Commercial_Poultry_Nutrition

44 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 14. Flaxseed to feed flaxseed for the entire grow-out period. Feeding 10% flaxseed to broilers for only the last Other Names: Linseed 14 d of grow-out, results in significant incorporation of omega-3 fatty acids in the meat. With cooked Nutritional Characteristics: breast + skin there is an increase in omega-3 con- tent from 150 675 mg/100 g cooked product. Flax is grown essentially for its oil content, although in Europe there is still some production Linolenic acid enriched eggs and poultry meat of special varieties for linen production. Fat- are therefore an attractive alternative to con- extracted flax, which is commonly called linseed sumption of oily fish. Linolenic acid is essentially meal, has traditionally been used for ruminant responsible for the characteristic smell of ‘fish oils’ feeds. Over the last few years, there has been and undoubtedly flax oil does have a ‘paint-type’ interest in feeding full-fat flaxseed to poultry, smell. There is some concern about the taste and because of its contribution of linolenic acid. Flax smell of linolenic acid-enriched poultry meat and oil contains about 50% linolenic acid (18:3w3) this topic needs more careful study with controlled which is the highest concentration of omega-3 taste panel work. There is often discussion fatty acids within vegetable oils. It has recent- about the need to grind flaxseed. The seeds are ly been shown that 18:3w3, and its desaturation very small, and for birds with an ‘immature’ products docosahexaenoic acid and eicos- gizzard it seems likely that some seeds will apentaenoic acid are important in human health, pass directly through the bird. Flaxseeds are quite and especially for those individuals at risk from difficult to grind, and are usually mixed 50:50 chronic heart disease. Government agencies in with ground corn before passing through a many countries now recognize the importance hammer mill. Perhaps the greatest benefit to of linolenic acid in human health, suggesting the grinding is seen with mash diets. Table 2.5 need to increase average daily intake, and shows digestible amino acid values, determined especially intake in relation to that of linoleic acid. with adult roosters for whole and ground flaxseed. Feeding flaxseeds to poultry results in direct These digestibility values were determined incorporation of linolenic acid into poultry using the force-feeding method, and so the bird meat and also into eggs. Feeding laying hens 10% is fed only the flaxseed, which is a novel flax results in a 10-fold increase in egg yolk situation to the bird. Over time gizzard linolenic acid content and eating two such activity may increase and so digestibility of modified eggs each day provides adults with most whole seeds may improve. Using a classical AMEn of their daily recommended allowance of bioassay, we have shown a consistent increase linolenic acid. For each 1% of flaxseed added in AMEn of flaxseed when diets are steam to a layer diet, there will be a +40 mg increase crumbled (Table 2.6). in total omega-3 fatty acids per egg. Likewise, in broilers, each 1% flaxseed addition will increase total omega-3 fats in the carcass by +2% of total fat. Feeding layers 8% flaxseed will result in an egg with about 320 mg total omega-3 fatty acids. For broiler chickens, there is no need SECTION 2.1 Description of ingredients

CHAPTER 2 45 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.5 Amino acid digestibility These problems can usually be overcome by of flaxseed (%) gradual introduction of flaxseed, using for ex - ample, 4% for one week, followed by 6% for Flaxseed another week and then the final 8-10% inclusion. It usually takes 15-20 d in order for omega-3 Methionine Whole Ground content of eggs to plateau at the desired level of Cystine 68 85 300 mg/egg. With prolonged feeding there is often Lysine 68 87 greater incidence of liver hemorrhage in layers, Threonine 72 88 even though mortality is rarely affected. Such Tryptophan 65 82 hemorrhaging occurs even in the presence of Arginine 85 95 100-250 IU vitamin E/kg diet, which is a Isoleucine 71 92 regular addition to flax-based diets. Disruption Valine 66 86 to liver function may become problematic if Leucine 65 84 other stressors occur. 67 87 Potential Problems: Courtesy Novus Int. Flaxseed should be introduced gradually Table 2.6 Effect of steam crumbling when feeding young layers. Weekly increments on AMEn of flaxseed (kcal/kg) using 4-6 and 8-10% over 3 weeks are ideal to pre- vent feed refusal. Ground flaxseed is prone to oxida- Bird Type Mash Steam tive rancidity, and so should be used Crumble within 2-3 weeks of processing. There seem to be advantages to steam pelleting diets contain-ing Broiler chicken 3560 4580 +31% flaxseed. Flaxseed contains a number of antinutrients including mucilage, trypsin inhibitor, Rooster 3650 4280 +17% cyanogenic glycosides and considerable quantities of phytic acid. The mucilage is main- Laying hen 3330 4140 +24% ly pectin, found in the seed coat and can be 5-7% by weight. The mucilage undoubtedly con- Adapted from Gonzalez (2000) and Bean (2002) tributes to more viscous excreta, and there is some evidence that ß-glucanase enzymes may be These assays were conducted at different of some benefit, especially with young birds. times and with different samples of flaxseed. In Flaxseed may contain up to 50% of the level of another study there was an 18% improvement trypsin inhibitors found in soybeans, and this is in AMEn for layers when flaxseed was extruded. possibly the basis for response to heat treatment Conventional pelleting seems sufficient to and steam pelleting of flaxseed. The main glucosides weaken the seed structure so as to allow greater yield hydrocyanic acid upon hydrolysis, and this digestibility of amino acids and energy. has an adverse effect on many enzyme systems involved in energy metabolism. With laying hens, there may be transitory problems with suddenly incorporating 8-10% flaxseed in the diet, usually manifested as reduced feed intake and/or wet sticky manure. SECTION 2.1 Description of ingredients

46 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Nutrient Profile: (%) Dry Matter 90.0 Methionine 0.41 Crude Protein 22.0 Methionine + Cystine 0.82 Metabolizable Energy: Lysine 0.89 35001-42002 Tryptophan 0.29 (kcal/kg) 14.64–17.60 Threonine 0.82 (MJ/kg) Arginine 2.10 Calcium 0.25 Av. Phosphorus 0.17 Dig Methionine 0.281-0.352 Sodium 0.08 Dig Meth + Cys 0.56-0.70 Chloride 0.05 Dig Lysine 0.64-0.78 Potassium 1.20 Dig Tryptophan 0.25-0.27 Selenium (ppm) 0.11 Dig Threonine 0.53-0.67 Fat 34.0 Dig Arginine 1.49-1.93 Linoleic acid 5.2 Crude Fiber 6.0 1 Mash; 2 Pellets Bulk Density: kg/m3 lb/ft3 lb/bushel 700 43.5 55.7 Formulation Constraints: Bird age Min. Max. Comments 0-4 wk 8 4-8 wk 8 Gradual introduction suggested > 8 wk 10 to prevent feed refusal. QA Schedule: Moisture CP Fat Ca/P AA’s Other All deliveries 6 mos 6 mos 12 mos 12 mos Fatty acid profile each 12 mos. SECTION 2.1 Description of ingredients

CHAPTER 2 47 INGREDIENT EVALUATION AND DIET FORMULATION 15. Meat meal from 75% to 55% and cystine from 65% down to 30%. If extreme pressure treatment becomes Other names: Meat and bone meal standard during rendering of meat meal, it will obviously be necessary to carefully re-evaluate Nutritional Characteristics: nutrient availability. Meat meal is a by-product of beef or swine pro- Recent evidence suggests that the metabolizable cessing, and this can be of variable composition. energy content of meat meal, and other animal For each 1 tonne of meat prepared for human con- protein by-products, is higher than the most sumption, about 300 kg is discarded as inedible common estimates used in the past. In bioassays, product, and of this, about 200 kg is rendered into ME values determined at inclusion levels of 5 –10% meat meal. In the past, meat meal referred only are much higher than those determined at more to soft tissue products, while meat and bone classical levels of 40 – 50% inclusion. The reason meal also contained variable quantities of bone. for the higher values is unclear, although it may Today, meat meal most commonly refers to ani- relate to synergism between protein or fat sources, mal by-products with bone where protein level and these are maximized at low inclusion levels. is around 50% and calcium and phosphorus are Alternatively, with very high inclusion levels of meat at 8% and 4% respectively. Because the miner- meal, the high calcium levels involved may al comes essentially from bone, the calcium cause problems with fat utilization due to soap phosphorus ratio should be around 2:1 and devi- formation, and so energy retention will be reduced. ations from this usually indicate adulteration Another reason for change in energy value, is that with other mineral sources. commercial samples of meat meal today contain less bone than occurred some 20 – 30 years ago. Variation in calcium and phosphorus content Dale suggests that the TMEn of meat meal from is still problematic, and the potential for over- beef is around 2,450 kcal/kg while that from feeding phosphorus is a major reason for upper pork is closer to 2,850 kcal/kg. limits of inclusion level. Meat meals usually contain about 12% fat and the best quality Another concern with meat meal is microbial meals will be stabilized with antioxidants such content, and especially the potential for con- as ethoxyquin. Some of the variability in tamination with salmonella. Due to increasing composition is now being resolved by so-called awareness and concern about microbial quality, ‘blenders’ that source various meat meal surveys show that the incidence of contamination products and mix these to produce more has declined, but remains at around 10%. Protein consistent meat meals. blends are at highest risk, because obviously a single contaminated source can lead to spread of Meat meals are currently not used in Europe salmonella in various blended products. One means because of the problems they have had with BSE of reducing microbial load is to treat freshly (Bovine Spongiform Encephalopathy). It seems processed meals with organic acids. In many stud- as though conventional rendering treatments ies, it is shown that meals are virtually sterile when do not inactivate the causative prions. However, pressure treatment to 30 psi (200 kPa) for about 30 minutes during or after rendering seems to destroy prions. Parsons and co-workers at the University of Illinois have shown that such pressure treatment can reduce lysine digestibility SECTION 2.1 Description of ingredients

48 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION they emerge from the cooking chambers, and that expanded diets will have much lower microbial problems most often occur with recontamination. counts than corresponding mash diets. Certainly most feed ingredients contain salmonella, however, because of the relative proportion of meat Unfortunately, there is variability in nutrient meals used in a diet, the actual chance of availability of conventionally rendered meat contamination for a single bird may, in fact, meal, where lysine digestibility, for example, can come from corn (Table 2.7). vary from 70 to 88%. Such variability is not highly correlated with simple in vitro assays The relative risk to an individual bird is, such as pepsin digestibility and KOH solubility. therefore, claimed to be higher from cereals because, even though they are not usually Potential problems: contaminated, their much higher inclusion level results in a greater potential risk. However, Meat meal should contain no more than this type of argument is open to the real criticism 4% phosphorus and 8% calcium, since higher that meat meals are much more likely to con- ash content will reduce its energy value. Nutrient taminate the feed, trucks, equipment etc., and availability is variable across suppliers, and so that salmonella numbers will likely increase it is important to have adequate quality control after feed manufacture. Pelleted and extruded/ procedures in place, and especially when there is a change in supplier. Table 2.7 Relative risk due to salmonella from various ingredients Corn Salmonella Diet Relative Vegetable proteins Contamination (%) Risk Factor Meat meals (%) 60 60 30 24 1 5 50 8 10 SECTION 2.1 Description of ingredients

CHAPTER 2 49 INGREDIENT EVALUATION AND DIET FORMULATION Nutrient Profile: (%) Dry Matter 90.0 Methionine 0.71 Methionine + Cystine 1.32 Crude Protein 50.0 Lysine 2.68 Tryptophan 0.36 Metabolizable Energy: Threonine 1.52 Arginine 3.50 (kcal/kg) 2450 - 2850 Dig Methionine 0.62 (MJ/kg) 10.25 - 11.92 Dig Meth + Cys 0.95 Dig Lysine 2.09 Calcium 8.0 Dig Tryptophan 0.26 Dig Threonine 1.17 Av. Phosphorus 4.0 Dig Arginine 2.78 Sodium 0.50 Chloride 0.90 Potassium 1.25 Selenium (ppm) 0.4 Fat 11.5 Linoleic acid 1.82 Crude Fiber - Bulk Density: kg/m3 lb/ft3 lb/bushel 394 37 47.4 Formulation Constraints: Bird age Min. Max. Comments 0-4 wk 6% Main concern is 4-8 wk 8% level of Ca and > 8 wk 8% P, and ash QA Schedule: Moisture CP Fat Ca/P AA’s Other All deliveries Yearly Fatty acid profile yearly. Salmonella each 3 months. SECTION 2.1 Description of ingredients

50 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 16. Poultry by-product meal Other Names: Poultry Meal, PBM Nutritional Characteristics: As for meat meal, poultry by-product meal products prior to heat processing. Ensiling is produced essentially from waste generated allows for more control over microbial con- during poultry meat processing. Because only tamination prior to processing, and allows the poten- one species is used, PBM should be a more tial to better utilize smaller quantities of poultry consistent product than is meat meal, and carcasses on-farm or from sites more distant to certainly calcium and phosphorus levels will be the PBM processing plant. Ensiling is also being lower. Variability in composition relates to considered as a means of handling spent layers whether or not feathers are added during processing prior to production of PBM. Poultry carcasses or or kept separate to produce feather meal. PBM offal do not contain sufficient fermentable car- and feathers are best treated using different bohydrate to allow lactic acid fermentation conditions, because feathers require more which will quickly reduce pH to about 4.2 and extreme heat in order to hydrolyze the keratin stabilize the product. These lactic acid produc- proteins. PBM with feathers may therefore ing microbes can therefore be encouraged to pro- mean that either the feather proteins are under- liferate by adding, for example, 10% molasses or cooked or that the offal proteins are overcooked. 10% dried whey to ground carcasses. These Overcooking usually results in a much darker mixtures quickly stabilize at around pH 4.2 – 4.5, colored product. PBM contains more unsaturated and can be held for 10 – 15d prior to manufac- fats than does meat meal, and so if much more ture of PBM. Carcasses from older birds may require than 0.5% fat remains in the finished product, slightly higher levels of theses carbohydrates, and it should be stabilized with an antioxidant. because of their inherently high fat content, may be mixed with products such as soybean meal Because of problems of disposal of spent in order to improve handling characteristics. layers, there is now some production of ‘spent Ensiled whole carcasses, as is now being produced hen meal’ which is essentially produced by with spent fowl, may present problems with rendering the whole body, including feathers. Such availability of feather proteins for reasons outlined spent hen meal contains around 11% fat and 20% previously in terms of ideal processing conditions ash, with 70% crude protein. Methionine, for tissue versus feathers. In the future, this TSAA and lysine in such samples are around 1.2%, problem may be resolved by adding feather- 2.5% and 3.5% respectively, with digestibility degrading enzymes to the ensiling mixture. of methionine and lysine at 85%, while cystine is closer to 60% digestible. As with poultry by- Potential problems: product meal, the ME of spent hen meal is influenced by content of ash, fat and protein, with Nutritive value will be positively correlated a mean value around 2,800 kcal/kg. with protein and fat content and negatively correlated with ash. Cystine content will give There is also current interest in ensiling an indication if feathers were included during various poultry carcasses and/or poultry by- processing, which will detract from amino acid digestibility. SECTION 2.1 Description of ingredients

CHAPTER 2 51 INGREDIENT EVALUATION AND DIET FORMULATION Nutrient Profile: (%) Dry Matter 90.0 Methionine 1.3 Crude Protein 60.0 Methionine + Cystine 3.3 Metabolizable Energy: Lysine 3.4 2950 Tryptophan 0.4 (kcal/kg) 12.34 Threonine 2.2 (MJ/kg) 3.60 Arginine 3.5 Calcium 2.10 Av. Phosphorus 0.36 Dig Methionine 1.1 Sodium 0.40 Dig Meth + Cys 2.3 Chloride 0.28 Dig Lysine 2.7 Potassium 0.90 Dig Tryptophan 0.3 Selenium (ppm) 8.50 Dig Threonine 1.8 Fat 2.50 Dig Arginine 3.0 Linoleic acid 1.9 Crude Fiber Bulk Density: kg/m3 lb/ft3 lb/bushel 578 36.0 46.1 FormulationConstraints: Bird age Min. Max. Comments 0-4 wk 8% 4-8 wk 10% No major concerns other > 8 wk 10% than fat stability QA Schedule: Moisture CP Fat Ca/P AA’s Other All samples Weekly Weekly Weekly Yearly Digestible amino acids, including cystine, yearly SECTION 2.1 Description of ingredients

52 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 17. Feather meal ly a reflection of higher than normal processing temperature, time and/or pressure, all of which Nutritional Characteristics: will adversely affect amino acid digestibility. Feather meal can be an excellent source of Feather meal also contains an amino acid crude protein where this is needed to meet called lanthionine, which is not normally found regulatory requirements. However, its use is severe- in animal tissue. Total lanthionine levels can there- ly limited by deficiencies of several amino acids, fore be used in assaying meat meal products for including methionine, lysine and histidine. potential contamination with feathers. Lanthionine Feather meal usually contains about 4.5 – 5.0% can occur as a breakdown product of cystine, and cystine, and this should be around 60% digestible. there are some research results which indicate The energy value of feather meal is quite high, a very good correlation between high lanthio- being around 3300 kcal ME/kg, and Dale and nine levels and poor digestibility of most other co-workers at the University of Georgia suggests amino acids. In most feather meal samples, TMEn of feather meal is highly correlated with lanthionine levels should be at 20 – 30% of total its fat content (2860 + 77 x % fat, kcal/kg). cystine levels. A potential problem in using Variability in quality is undoubtedly related to lanthionine assays in quality control programs, control over processing conditions. Feathers are is that it is readily oxidized by performic acid, partially dried and then steam-treated to induce which is a common step used in preparation of hydrolysis, and within reason, the higher the samples for amino acid analysis and particularly temperature and/or longer the processing time, where cystine levels are of interest. the better the chance of complete hydrolysis. Obviously extreme processing conditions will cause As with other animal proteins, there is current destruction of heat-labile amino acids such as interest in alternate methods of processing. lysine. As a generalization, the lower the pro- Treating feathers with enzyme mixtures that pre- cessing and drying temperatures, the lower the sumably contain keratinase enzyme together level of cystine digestibility. Research has shown with NaOH has been shown to improve overall processing conditions to result in digestible protein digestibility and bird performance. More cystine levels as low as 45% with low cooking recently, it has been shown that a pre-fermenta- temperature, to as high as 65% with higher tion with bacteria such as Bacillus licheniformis temperatures for longer durations. Because for 5 d at 50ºC, produces a feather lysate that is feather meal is an important contributor to comparable in feeding value to soybean meal when TSAA in the diet, the level of digestible cystine amino acid balance is accounted for. is a critical factor in evaluating nutritive value. Potential problems: High pressure, unless for a short duration, seems to reduce amino acid digestibility, and again Amino acid digestibility, and especially this is especially critical for cystine. Under cystine digestibility is greatly influenced by extreme processing conditions it seems as though processing conditions. Monitoring total sulfur sulfur can be volatilized, likely as hydrogen levels may be a simple method of assessing sulfide, and so another simple test for protein consistency of processing conditions. quality, is total sulfur content. Sulfur level should be just over 2%, and any decline is like- SECTION 2.1 Description of ingredients

CHAPTER 2 53 INGREDIENT EVALUATION AND DIET FORMULATION Nutrient Profile: (%) Dry Matter 90.0 Methionine 0.60 Crude Protein 85.0 Methionine + Cystine 6.10 Metabolizable Energy: Lysine 1.72 3000 Tryptophan 0.60 (kcal/kg) 12.55 Threonine 4.51 (MJ/kg) 0.20 Arginine 6.42 Calcium 0.70 Av. Phosphorus 0.70 Dig Methionine 0.47 Sodium 0.40 Dig Meth + Cys 2.85 Chloride 0.30 Dig Lysine 1.10 Potassium 0.72 Dig Tryptophan 0.41 Selenium (ppm) 2.50 Dig Threonine 3.15 Fat 0.10 Dig Arginine 5.05 Linoleic acid 1.50 Crude Fiber Bulk Density: kg/m3 lb/ft3 lb/bushel 460 28.7 36.7 Formulation Constraints: Bird age Min. Max. Comments 0-4 wk 2% Amino acid 4-8 wk 3% digestibility the > 8 wk 3% main concern QA Schedule: Moisture CP Fat Ca/P AA’s Other 6 mos All deliveries Weekly Monthly 6 mos Total sulfur each 3 months SECTION 2.1 Description of ingredients

54 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 18. Fish meal Other names: Herring meal; White Fish meal; Menhaden meal Nutritional Characteristics: fishmeal, especially from fresh water fish, there is also the potential problem of excessive Because of the decline in activities of most thiaminase activity. Depending upon geographical fisheries directed at human consumption, fish meals location, taint in eggs and meat can be detected are now almost exclusively produced from by consumers when birds are fed much more than smaller oily fish caught specifically for meal 4 – 5% fish meal. Problems of taint will be manufacture. Menhaden and anchovy are the more acute with high fat samples, and of course, main fish species used for meal manufacture, with the problems are most acute if fish oil per se is used. lesser quantities of herring meal produced in Even at levels as low as 2.5% fish meal, some brown Europe. Fish meal is usually an excellent source egg birds produce tainted eggs which may be relat- of essential amino acids, while energy level is ed to the trimethylamine content of fish meal, and largely dependent upon residual oil content. the genetic predisposition of certain birds failing Because of variable oil and protein content, to produce sufficient trimethylamine oxidase. expected ME value can be calculated based Excess trimethylamine is shunted to the egg, pro- on knowledge of their composition in the meal. ducing a characteristic fishy taint (see also canola meal). The trimethylamine content of fish meal ME (kcal/kg) = 3000 ± (Deviation in % fat x is around 50 – 60 mg/kg, and assuming a 2.5% 8600) ± (Deviation in % CP x 3900) inclusion level, and feed intake of such brown egg Where standard fat content is 2%, and CP is 60%. layers of 115 g/day, means that the bird is taking in about 0.2 mg/day. Each affected egg con- Therefore, a 4% fat, 63% CP sample is tains around 0.8 mg, and so, it is obvious that the expected to have an ME of 3289 kcal/kg, while diet contains sources of trimethylamine other a 1% fat, 58% CP sample will have ME closer than fish meal, or that there is microbial synthe- to 2836 kcal/kg. The ash content of fishmeal will sis in the intestine. be predominantly calcium and phosphorus and the latter can be around 90% available, as is For young chicks, and especially the broil- phosphorus from any quality animal protein. er chicken, a major concern with feeding fish meal, is gizzard erosion. A proportion of chicks fed All fish meals should be stabilized with almost any level of fish meal develop gizzard antioxidants. This is especially true for high oil lesions, although there is a strong dose-response. content samples, but even with only 2% Affected birds have signs ranging from small residual oil, there is good evidence to show localized cracks in the gizzard lining, through reduced oxidation (in terms of production of to severe erosion and hemorrhage which ultimately oxidation products and free fatty acids, as well leads to total destruction of the lining. The as reduced heat production) by adding 100 thick lining is required for preventing degrading ppm ethoxyquin during manufacture. effects of acid and pepsin produced by the proventriculus. Because of disrupted protein Potential problems in feeding fish meal are taint of both eggs and meat, and gizzard erosion in young birds. With inadequately heat-treated SECTION 2.1 Description of ingredients

CHAPTER 2 55 INGREDIENT EVALUATION AND DIET FORMULATION degradation, the affected birds show very slow potent in causing gizzard erosion. Currently the growth rate. The condition is most common when only useful screening test is to feed high levels fish meal is included in the diet, although (25 – 50%) to young chicks and score the degree similar signs are seen with birds fed a high level of gizzard lesions (see ingredient quality control of copper (250 ppm) or vitamin K deficient Section 2.2 i). diets, or simply induced by starvation. Gizzard erosion was initially thought to be associated with Because the mode of action of gizzerosine histamine levels in fish meal. Feeding histamine is via acid production and a change in gizzard to birds simulates the condition, as does feed- pH, there have been attempts at adding buffers ing a heated semi-purified diet containing his- to prevent the problem. For example adding tidine. Fish meals contain histamine, and following sodium bicarbonate has been reported to lessen microbial degradation during pre-cooking stor- the severity of gizzard erosion. However, age, bacteria possessing histidine decarboxy- levels as high as 10 kg/tonne are required to change lase will convert variable quantities from histi- gizzard pH by only 0.3 units. Variable levels of dine to histamine. Histamine has the effect of gizzerosine in fish meals likely relate to stimulating excessive acid production by the pre-processing holding time and storage proventriculus, and it is this acid environment temperature, and also to the time and temper- that initiates breakdown of the gizzard lining. A ature of the cooking and oil extraction procedures. product known as gizzerosine has been isolated from fish meal, and this has Potential Problems: histamine-type properties in terms of stim- ulating acid secretion. Gizzerosine is formed by Taint of meat or eggs can occur with much heating histidine and a protein during manufacture more than 2% fish meal in the diet. Fish meal of fish meal. The most common components are should be stabilized with an antioxidant, and this lysine and histidine. Gizzerosine is almost 10x factor is critical when residual fat content as potent as is histamine in stimulating proven- exceeds 2%. With young chicks, gizzard erosion tricular acid production and some 300x more is a consequence of using poorly processed, or inadequately stored fish meal. SECTION 2.1 Description of ingredients

56 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Nutrient Profile: (%) Dry Matter 90.0 Methionine 1.82 Crude Protein 60.0 Methionine + Cystine 2.92 Metabolizable Energy: Lysine 5.28 2750 Tryptophan 0.58 (kcal/kg) 11.51 Threonine 3.01 (MJ/kg) 6.50 Arginine 4.05 Calcium 3.50 Av. Phosphorus 0.47 Dig Methionine 1.62 Sodium 0.55 Dig Meth + Cys 2.42 Chloride 0.32 Dig Lysine 4.72 Potassium 1.85 Dig Tryptophan 0.48 Selenium (ppm) 2.0 Dig Threonine 2.50 Fat 0.3 Dig Arginine 3.62 Linoleic acid 1.0 Crude Fiber Bulk Density: kg/m3 lb/ft3 lb/bushel 674 42 53.8 Formulation Constraints: Bird age Min. Max. Comments 0-4 wk 8% Taint problems likely in most 4-8 wk 10% markets at levels much in excess > 8 wk 10% of 2% QA Schedule: Moisture CP Fat Ca/P AA’s Other All deliveries Monthly 12 mos Fat oxidation, gizzerosine each 6 mos. SECTION 2.1 Description of ingredients

CHAPTER 2 57 INGREDIENT EVALUATION AND DIET FORMULATION 19. Fats and oils content of free fatty acids. Also, dependent upon the degree of heating that they have been Nutritional Characteristics: subjected to, these greases can contain significant quantities of undesirable break-down products. Fats provide a concentrated source of energy, and so relatively small changes in inclusion In order to ensure adequate levels of linole- levels can have significant effects on diet ME. Most ic acid, and to improve palatability and reduce fats are handled as liquids, and this means dustiness of diets, all diets require a minimum heating of most fats and fat blends that contain of 1% added fat, regardless of other economic appreciable quantities of saturated fatty acids. or nutritional considerations. There is consid- erable information published on factors that Depending upon the demands for pellet influence fat digestibility, but in most instances, durability, 3 – 4% is the maximum level of fat that this knowledge is not used during formulation. can be mixed with the other diet ingredients. To In large part variability is due to the fact that this, up to 2 – 3% can be added as a spray-on digestibility is not a static entity for any fat, but coat to the formed pellet. Alternate technology rather its utilization is variable with such factors of spraying fat onto the hot pellet as it emerges as bird age, fat composition and inclusion level. from the pellet die means that much higher Unfortunately, these variables are difficult to inclusions are possible since the hot pellet factor into formulation programs. Other concerns seems better able to adsorb the fat. Under about fats are their potential for rancidity and effect these conditions, there is concern for manufacturers on carcass composition. Following are descrip- who demand extreme pellet durability, since fines tions of the major types of fat used in the feed will already be treated with extra fat, prior to their industry. Table 2.8 summarizes the fatty acid recycling through the pellet mill. profile and ME of the most common fat sources used in poultry nutrition. An attempt has been All fats and oils must be treated with an made to predict fat ME based on bird age. antioxidant which ideally should be added at the point of manufacture. Fats held in heated tanks 19a. Tallow at the mill must be protected from rancidity. The more unsaturated a fat, the greater the chance Tallow has traditionally been the principle fat of rancidity. Fats also provide varying quantities source used in poultry nutrition. However, over the of the essential nutrient linoleic acid. Unless a last 10 years, there has been less use of pure tallow diet contains considerable quantities of corn, it and greater use of blended fats and oils. Tallow is may be deficient in linoleic acid, because all diets solid at room temperature and this presents some should contain a minimum of 1%. A major prob- problems at the mill, especially when heated lem facing the industry at the moment is the increasing use of restaurant grease in feed-grade fats. These greases are obviously of variable composition in terms of fatty acid profile and SECTION 2.1 Description of ingredients

58 SECTION 2.1 Table 2.8 Nutrient composition of CHAPTER 2 Description of ingredients fats and oils INGREDIENT EVALUATION AND DIET FORMULATION Metabolizable Fatty acid profile (%) energy Fat M.I.U.5 (kcal/kg) Ingredient 11 22 % % 12:0 14:0 16:0 18:0 16:1 18:1 18:2 18:3 19a Tallow 19b Poultry fat 7400 8000 98 2 4.0 25.0 24.0 0.5 43.0 2.0 0.5 19c Fish oil 19d Vegetable oil 8200 9000 98 2 1.0 20.0 4.0 5.5 41.0 25.0 1.5 19e Coconut oil 19f Palm oil 8600 9000 99 1 8.0 21.0 4.0 15.0 17.2 4.4 3.03 19g Vegetable soapstock 19h Animal-Vegetable blend 8800 9200 99 1 0.5 13.0 1.0 0.5 31.0 50.0 2.0 19i Restaurant grease 7000 8000 99 1 50.04 20.0 6.0 2.5 0.5 4.0 2.1 0.2 7200 8000 99 1 2.0 42.4 3.5 0.7 42.1 8.0 0.4 7800 8100 98 2 0.3 18.0 3.0 0.3 29.0 46.0 0.8 8200 8600 98 2 2.1 21.0 15.0 0.4 32.0 26.0 0.6 8100 8900 98 2 1.0 18.0 13.0 2.5 42.0 16.0 1.0 1ME for young birds up to 3 weeks of age; 2ME for birds after 3 weeks of age; 3Contains 25% unsaturated fatty acids 20:4; 4Contains 15% saturated fatty acids 10:0; 5Moisture, impurities, unsaponifiables.

CHAPTER 2 59 INGREDIENT EVALUATION AND DIET FORMULATION fats are added to very cold ingredients originating makes them uneconomic for animal feeds. from unheated outside silos. Being highly Most vegetable oils provide around 8700 kcal saturated, tallow is not well digested by young ME/kg and are ideal ingredients for very young chickens, although there is some evidence of birds. If these oils are attractively priced as better utilization by young turkeys. The digestibil- feed ingredients, then the reason(s) for refusal by ity of tallow can be greatly improved by the the human food industry should be ascertained addition of bile salts suggesting this to be a e.g. contaminants. limiting feature of young chicks. However, the use of such salts is not economical and so 19e. Coconut Oil inclusion of pure tallow must be severely restricted in diets for birds less than 15 – 17 d of age. Coconut oil is a rather unusual ingredient in that it is a very saturated oil. Coconut oil is more 19b. Poultry Fat saturated than is tallow. It contains 50% of saturated fatty acids with chain length less than This fat source is ideal for most types and ages 12:0. In many respects, it is at the opposite end of poultry in terms of its fatty acid profile. Due of the spectrum to fish oil in terms of fatty acid to its digestibility, consistent quality and residual profile. There has been relatively little work flavor, it is in high demand by the pet food conducted on the nutritional value of coconut industry, and this unfortunately reduces its oil, although due to its saturated fatty acid content supply to the poultry industry. As occurs with poul- it will be less well digested, especially by young try meal, there is a concern with integrated birds. However recent evidence suggests very poultry operations that fat-soluble contaminants high digestibility by young birds of medium may be continually cycled (and concentrated) chain triglycerides, such as C:8 and C:10 as through the birds. This can obviously be resolved found in coconut oil. These medium length fatty by breaking the cycle for a 1 or 2 bird cycle. acids do not need bile for emulsification or prior incorporation within a micelle prior to 19c. Fish Oil absorption. There is current interest in the use of fish oils 19f. Palm Oil in diets for humans and animals, since its distinctive component of long chain fatty acids is thought Palm oil production is now only second to beneficial for human health. Feeding moderate soybean oil in world production. Palm oil is levels of fish oils to broiler chickens has been produced from the pulpy flesh of the fruit, while shown to increase the eicosapentaenoic acid smaller quantities of palm kernel oil are extracted content of meat. However, with dietary levels in from the small nuts held within the body of the excess of 1%, distinct fish type odour is often fruit. Palm oil is highly saturated, and so will have present in both meat and eggs, which is due limited usefulness for very young birds. Also, soap- mainly to the contribution of the omega-3 fatty acids. stocks produced from palm oil, because of their free fatty acid content, will be best suited for older 19d. Vegetable Oil birds. There is potential for using palm and coconut oils as blends with more unsaturated oils A large range of vegetable oils is available as and soapstocks, so as to benefit from potential an energy source, although under most situations, fatty acid synergism. competition with the human food industry SECTION 2.1 Description of ingredients

60 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 19g. Soapstock (Acidulated soapstock) and restaurant chains have changed to hydro- genated vegetable cooking fats and oils. The fats As a by-product of the vegetable oil refining are hydrogenated to give them protection against industry, soapstocks provide a good source of high-temperature cooking. Today, restaurant energy and essential fatty acids. Soapstocks greases contain higher levels of oleic acid, and can be quite high in free fatty acids, and so much of this will be trans-oleate. Assuming there stabilization with an antioxidant is essential. has not been excessive heating, and that the grease Soapstocks may also be acidulated, and this has been cleaned and contains a minimum of may pose problems with corrosion of metallic impurities, then the energy value will be equipment. Some impurities may be added to comparable to that of poultry fat. Future use of soapstocks as a means of pollution-free non-fat ‘cooking fats’ will lead to considerable disposal by refineries, and therefore quality variation in the nutrient profile of these products. control becomes more critical with these products. Moisture level may also be high in some 19j. Conjugated Linoleic Acid (CLA) samples, and this simple test is worthwhile for economic evaluation. CLA is an isomer of conventional linoleic acid, but unlike linoleic, there are numerous health 19h. Animal-Vegetable Blend Fat benefits claimed for CLA. It is claimed to help control glucose metabolism in diabetic mammals, Some manufacturers mix animal and vegetable and more importantly to prevent and/or control based fats, to give so-called blended products. the growth of certain cancerous tumors. CLA is The vegetable source is usually soapstock normally found in dairy products, represent- material. The blend has the advantage of allowing ing around 0.3% of total fat. Turkey meat is also for some synergism between saturated fatty high in CLA. Feeding CLA to layers results in acids of animal origin and unsaturates from the bioaccumulation in the egg, much as for any fatty soapstock. Animal-vegetable blends are there- acid, and so there is potential for producing CLA fore ideally suited for most classes of poultry enriched designer eggs. It seems as though the without the adverse problem of unduly increasing AMEn of CLA is comparable to that of linoleic the unsaturates in meat which can lead to increased acid, suggesting that the two fatty acids are rate of oxidative rancidity (reduced shelf life). comparably metabolized. 19i. Restaurant Grease It is possible that CLA is not elongated as in linoleic acid during metabolism and so this has An increasing proportion of feed fats is posed questions about adequacy of prostaglandin now derived from cooking fats and oils, and the synthesis, and hence immune function. There generic product is termed restaurant grease. Its are some reports of altered lipid metabolism in use has increased mainly due to problems of embryos and young chicks from eggs hatched from alternate disposal. Traditionally restaurant hens fed 1 g CLA daily. There is some discussion greases were predominately tallow or lard based about whether or not synthetic sources of CLA products and this posed some problems in actually mimic the beneficial anti-cancerous collection and transportation of the solid properties of ‘natural’ CLA found in dairy material. In recent years, due to consumer products. concerns about saturated fats, most major fast food SECTION 2.1 Description of ingredients

CHAPTER 2 61 INGREDIENT EVALUATION AND DIET FORMULATION Important Considerations: free radical then becomes very susceptible to attack by atmospheric oxygen (or mineral oxides) to form Fats and oils are probably the most problem- unstable peroxide free radicals. These peroxide atic of all the ingredients used in poultry feeds.They free radicals are themselves potent catalysts, require special handling and storage facilities and so the process becomes autocatalytic and and are prone to oxidation over time. Their fatty rancidity can develop quickly. Breakdown acid profile, the level of free fatty acids and degree products include ketones, aldehydes and short of hydrogenation can all influence digestibility. Unlike chain fatty acids which give the fat its characteristic most other ingredients, fat digestion can be age ‘rancid’ odour. Animal fats develop a slight dependent, since young birds have reduced abil- rancid odour when peroxide levels reach 20 ity to digest saturated and hydrogenated fats. meq/kg while for vegetable oils problems start at around 80 meq/kg. a. Moisture, Impurities, Unsaponifiables Oxidative rancidity leads to a loss in energy Feed grade fats will always contain some value, together with the potential degradation of non-fat material that is generally classified as M.I.U. the bird’s lipid stores and reserves of fat- (moisture, impurities and unsaponifiables). soluble vitamins. Fortunately we have some Because these impurities provide no energy or control over these processes through the judicious little energy, they act as diluents. A recent use of antioxidants. Most antioxidants essentially survey indicated M.I.U’s to range from 1 – 9%. function as free radical acceptors – these Each 1% MIU means a loss in effective value of radical-antioxidant complexes are, however, the fat by about $3 - $4/tonne, and more stable and do not cause autocatalytic reactions. importantly, energy contribution will be less Their effectiveness, therefore, relies on adequate than expected. The major contaminants are dispersion in the fat immediately after process- moisture and minerals. It seems as though ing. As an additional safety factor, most diets will moisture can be quickly detected by Near Infra also contain an antioxidant added via the premix. Red Analysis. Moisture and minerals also lead The Active Oxygen Method (AOM) is most com- to increased peroxidation. monly used to indicate potential for rancidity. After 20 h treatment with oxygen, quality fats should b. Rancidity and Oxidation develop no more than 20 meq peroxides/kg. The feeding value of fats can obviously be Time is a very important factor in the AOM affected by oxidative rancidity that occurs prior test, because peroxides can break down and to, or after feed preparation. Rancidity can disappear with extended treatment. For this influence the organoleptic qualities of fat, as well reason, some labs will provide peroxide values as color and ‘texture’ and can cause destruction at 0, 10 and 20 hr. A newer analytical technique of other fat soluble nutrients, such as vitamins, is the Oil Stability Index (OSI). This is similar to both in the diet and the bird’s body stores. AOM, but instead of measuring initial peroxide Oxidation is essentially a degradation process that products, measures the accumulation of secondary occurs at the double-bond in the glyceride breakdown compounds. The assay is highly auto- structure. Because presence of double-bonds infers mated and records the time necessary to produce unsaturation, then naturally the more unsaturated a given quantity of breakdown products such as a fat, the greater the chance of rancidity. The short chain volatile fatty acids. initial step is the formation of a fatty free radical when hydrogen leaves the -methyl carbon in SECTION 2.1 the unsaturated group of the fat. The resultant Description of ingredients

62 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION c. Fatty Acid Profile energy of the 50:50 mixture of the unsaturated oleic acid with the saturated palmitic acid, is 5% Fat composition will influence overall fat higher than the expected value based on the mean utilization because different components are value of 2710 kcal/kg. We therefore have a boost digested with varying efficiency. It is generally of 5% in available energy that likely comes recognized that following digestion, micelle from greater utilization of the palmitic acid formation is an important prerequisite to absorp- because of the presence of the unsaturated tion. Micelles are complexes of bile salts, fatty oleic acid. acids, some monoglycerides and perhaps glycerol. The conjugation of bile salts with This type of synergism can, however, have a fatty acids is an essential prerequisite for confounding effect on some research results. If transportation to and absorption through we want to measure the digestibility of corn, it the microvilli of the small intestine. Polar is possible to feed just corn for a short period of unsaturated fatty acids and monoglycerides time and conduct a balance study. For obvious readily form this important association. However, reasons, it is impossible to feed only fats, and we micelles themselves have the ability to have to conduct studies involving graded fat solubilize non-polar compounds such as satu- additions to a basal diet, with extrapolation of rated fatty acids. Fat absorption is, therefore, results to what would happen at the 100% dependent upon there being an adequate feeding level. In these studies, we assume the supply of bile salts and an appropriate balance difference in digestibility between any two diets of unsaturates:saturates. is due solely to the fat added to the diet. If, because of synergism, the added fat improved digestibility Taking into account the balance of saturated of basal diet components, then this ‘boost’ in to unsaturated fatty acids can be used to advan- digestibility is attributed to the fat and an erro- tage in designing fat blends. This type of synergistic neously high value is projected. However, it can effect is best demonstrated using pure fatty acids be argued that this ‘boost’ to fat’s value occurs (Table 2.9). In this study, the metabolizable normally when fats are added to diets, and that these higher values more closely reflect the Table 2.9 Metabolizable energy of practical value of fat in a poultry diet. We have layer diets containing various fatty proposed this synergism to account for some of acids the so-called ‘extra-caloric’ effect of fat often seen in reported values, where metabolizable Determined Expected energy can sometimes be higher than corresponding gross energy values (which ME (kcal/kg) theoretically cannot occur). Table 2.10 shows results from this type of study where corn oil was Oleic 2920 assayed using different types of basal diet. Palmitic 50:50 mixture 2500 2850 (+5%) 2710 (Atteh and Leeson, 1985) SECTION 2.1 Description of ingredients

CHAPTER 2 63 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.10 Variation in ME value of various levels of free fatty acids (soapstock of the corn oil attributed to fatty acid respective fat). Table 2.11 shows a summary of saturation of the basal diet these results, indicating energy values for the respective fats containing the highest and Basal diet Corn oil ME lowest levels of free fatty acids used. (kcal/kg) Predominantly unsaturated Table 2.11 Effect of level of free Predominantly saturated 8390a fatty acid and bird age on fat ME Corn-soy diet 9380b value (kcal/kg) 8510a When the basal diet contains saturated fatty Tallow 13% FFA Age 54 d acids, there is an apparent increase in the ME of 95% FFA 10 d 7940 corn oil. This effect is possibly due to the unsat- 7460 6830 urates in corn oil aiding in utilization of the basal Palm 6% FFA 4920 diet saturates. However, because of methods of 92% FFA diet substitution and final ingredient ME 6690 7800 calculation, any such synergism is attributed Soy 14% FFA 3570 6640 to the test ingredient (corn oil). 68% FFA 9290 9300 ME values of fats will therefore vary with 8000 8480 inclusion level, although this effect will be influenced by degree of fat saturation. A ratio Adapted from Wiseman and Salvador (1991) of 3:1, unsaturates:saturates is a good compro- mise for optimum fat digestibility for all ages of These data suggest that free fatty acids are more bird. However, this ratio may not be the most problematic when the fat is predominantly economical type of fat to use, because of the saturated and this is fed to young birds. Contrary increased cost of unsaturates relative to saturates. to these results, others have shown comparable results with broilers grown to market weight d. Level of Free Fatty Acids and Fatty and fed tallows of varying free fatty acid content. Acid Hydrogenation Hydrogenation of fats becomes an issue Concern is often raised about the level of free with the general use of these fats in restaurants, fatty acids in a fat, because it is assumed these and the fact that restaurant grease is now a are more prone to peroxidation. Acidulated common, and sometimes the major compo- soapstocks of various vegetable oils contain nent of feed-grade fat blends. Hydrogenation the highest levels of free fatty acids, which can results in a high level of trans oleic acid (40 – 50%) reach 80 – 90% of the lipid material. For young and such vegetable oils have physical characteristics birds there is an indication that absorption of fatty similar to those of lard. There seems to be no acids is highest in birds fed triglycerides rather problem in utilization of these hydrogenated fats than free fatty acids and this may relate to less by poultry with ME values of restaurant greases efficient micelle formation or simply to less being comparable to those of vegetable oils. The bile production. Wiseman and Salvadore (1991) long-term effect of birds eating trans fatty acids demonstrated this effect in studying the ME is unknown at this time. value of tallow, palm oil and soy oil that contained SECTION 2.1 Description of ingredients

64 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION e. Bird Age and Bird Type g. Variable ME Values Young birds are less able to digest saturated It seems obvious that the use of a single fats, and this concept has been known for some value for fat ME during formulation is a com- time. With tallow, for example, palmitic acid promise, considering the foregoing discussion on digestibility increases from 50 to 85% through factors such as inclusion level, bird age, soap 14 to 56 d of age, which together with corre- formation etc. Table 2.8 gives different ME sponding changes for other fatty acids means that values for birds younger or older than 21 d, and tallow ME will increase by about 10% over this this in itself is a compromise. Following is an time period. The reason why young birds are less attempt to rationalize the major factors affecting able to digest saturated fats is not well understood, ME of a given fat, although it is realized that such although it may relate to less bile salt production, variables are not easily incorporated within a less efficient recirculation of bile salt or less formulation matrix (Table 2.12). production of fatty acid binding protein. Table 2.12 Factors affecting fat ME f. Soap Formation values When fats have been digested, free fatty Relative fat ME acids have the opportunity of reacting with other nutrients. One such possible association 28 d+ 100% is with minerals to form soaps that may or may not be soluble. If insoluble soaps are formed, there Bird age: 7 - 28 d 95% is the possibility that both the fatty acid and the Free fatty mineral will be unavailable to the bird. There is acids: 1–7d 88% substantial soap formation in the digesta of broiler chicks and this is most pronounced with Inclusion level: 0 – 10% (esp. for saturates) saturated fatty acids, and with increased levels Calcium level: 10 – 20% of diet minerals. Such increased soap production 20 – 30% 102% is associated with reduced bone ash and bone 100% calcium content of broilers. Soap production seems 30%+ 96% to be less of a problem with older birds. This is 92% of importance to laying hens that are fed high levels of calcium. In addition to calcium, other 1% (esp. for saturates) minerals such as magnesium can form soaps with 2% saturated fatty acids. In older birds and some other 3% 100% animals, there is an indication that while soaps 4% 100% form in the upper digestive tract, they are 5%+ 98% subsequently solubilized in the lower tract due <1% 96% to changes in pH. Under these conditions both >1% 94% the fatty acid and mineral are available to the bird. 100% Control over digesta pH may, therefore, be an 96% important parameter for control over soap formation. (esp. for birds <56 d of age) SECTION 2.1 Description of ingredients

CHAPTER 2 65 INGREDIENT EVALUATION AND DIET FORMULATION h. Trans Fatty Acids fats used in the feed industry will contain higher proportions of trans fatty acids than occurred some Trans fatty acids are isomers of naturally 20 years ago. It is thought that ‘overused’ frying occurring cis fatty acids. Trans fatty acids are often oil, that contains trans fatty acids as well as produced by the process of hydrogenation, as oxidized and polymerized materials, is harmful commonly occurs in production of margarine and to human health. These trans fatty acids can be other cooking fats. Hydrogenated (stabilized) found in human adipose tissue, and have been soybean oil, which is a common component of associated with immune dysfunction and cooking oils, contains around 20% trans fatty acids. unusual lipid metabolism in heart tissue. There With increasing use of restaurant grease in is very little information available on the effect animal fats and fat blends, it seems inevitable that of trans fatty acids on health of broilers or layers. OTHER INGREDIENTS lysine and 1% methionine plus cystine. The ME value is around 3200 kcal/kg, making these 20. Oats oats comparable to wheat in most characteristics. As with regular oats, ß-glucans can still be Oats are grown in cooler moist climates problematic and their adverse effect can be although they are of minor importance on a glob- overcome with use of exogenous enzymes, and al scale, representing only about 1.5% of total to a lesser extent antibiotics such as neomycin. cereal production. Most oats are used for ani- Much of the phosphorus in naked oats is as mal feed, and about 85% of this quantity is phytic acid, and so availability is very low. used locally and there is little trade involved. The There have been some reports of reduced hull represents about 20% of the grain by weight, skeletal integrity in birds fed naked oats unless and so this dictates the high fiber – low energy this reduced phosphorus availability is taken characteristics of oats. The amino acid profile into account. There are reports of broilers is however quite good, although there is some performing well with diets containing up to variation in protein and amino acid levels due 40% naked oats, and with layers, up to 50% has to varietal and seasonal effects. The best predictor been used successfully. of the energy value of oats, is simply the crude fiber content which is negatively correlated 21. Rye with ME. Oat lipids are predominantly oleic and linoleic acid, although a relatively high pro- Although the nutrient content of rye is essen- portion of palmitic acid leads to a ‘harder’ fat being tially similar to that of wheat and corn, its deposited it the bird’s carcass. feeding value for poultry is poor due to the presence of various antinutritional factors. Rye As for other small grains, oats contain an appre- contains a water insoluble fraction, which if ciable quantity of ß-glucans, and these cause prob- extracted, improves its feeding value. Various other lems with digesta and excreta viscosity. Most oats treatments such as water soaking, pelleting, contain about 3-7% ß-glucans and so with irradiation and the dietary supplementation of moderate inclusion levels of oats in a poultry diet various antibiotics all help to improve the growth it may be advantageous to use supplemental ß- of chicks fed rye. glucanase enzyme. There has been some inter- est in development of so-called naked oats, SECTION 2.1 which are similar in composition to oat groats. Description of ingredients Naked oats contain up to 17% CP with 0.68%

66 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION One of the most noticeable effects of feeding 23. Molasses rye, other than reduced performance is the production of a very sticky and wet excreta. Molasses is a by-product of the sugar refining The sticky droppings are due to the pectin-like industry, where either sugar beet or sugar cane components present in rye. Structural arabinoxylans, are used as raw materials. Because of a high water present in rye endosperm cell walls, are respon- content and concomitantly low energy value, it sible for creating the viscous digesta. These is only used extensively in poultry diets in areas viscous products reduce the rate of diffusion of close to sugar refineries. The molasses usually other solutes in the digesta so affecting nutrient available for animal feeding is so called final or uptake from the gut. In recent years enzyme blackstrap molasses, which is the product preparations have been developed that markedly remaining after most of the sugar has been reduce the antinutritional factor and eliminate the extracted for human consumption. Depending wet-sticky fecal problem with rye based diets. upon local conditions, high-test and type A and B molasses are sometimes available. The 22. Triticale high-test product is basically unrefined cane or beet juice that has had its sugars inverted to Triticale is a synthetic small grain cereal prevent crystallization. Type A and B molasses resulting from the intergeneric cross of wheat and are intermediate to final molasses. As expected, rye. Its higher yield per acre, as compared to rye the energy level of molasses decreases as more or wheat, make it of agronomic interest in areas and more sugar is extracted. Molasses is usually of the world not suitable for corn production. quantitated with a Brix number, measured in Numerous cultivars have been developed with degrees, and these numbers relate very closely protein contents varying from 11 to 20% and to the sucrose concentration in the product. amino acid balance comparable to wheat and Both cane and beet molasses contain about superior to that of rye. Energy content is also 46 - 48% sugar. similar to that of wheat and superior to that of rye. Like wheat, triticale has a significant Although molasses contains relatively little phytase content and so is a better source of energy and protein, it can be used to advantage to available phosphorus than other cereals such as stimulate appetite and to reduce dustiness of feed. corn or milo. There are reports of increased For example, feed intake is usually increased in birds enhancement of other dietary phosphorus with such as young Leghorn pullets, if molasses is triticale supplementation. The starch content of poured directly onto feed in the feed trough. It is triticale is as digestible as that of wheat and doubtful that molasses improves ‘taste’ of feed presents no wet litter or sticky manure problem. under these conditions, rather it presents a novel Where triticale is available, high levels can be used feed texture to the bird. A major problem with in poultry diets without any adverse molasses is a very high potassium content, at 2.5 problems. Similar to wheat and rye it contains – 3.5%, which has a laxative effect on birds. little or no xanthophylls and with fine grinding can While most birds perform well on balanced diets result in beak impaction with young birds. Also containing up to 2% molasses, inclusion levels much like wheat its feeding value can be increased by above 4% will likely result in increased water appropriate enzyme supplementation of the diet. intake and increased manure wetness. SECTION 2.1 Description of ingredients

CHAPTER 2 67 INGREDIENT EVALUATION AND DIET FORMULATION 24. Dehydrated Alfalfa 25. Full-fat Canola Seeds Dehydrated alfalfa meal can be quite high in The nutrient profile of canola seed makes it an protein (18 – 20%) although because the ideal ingredient for high nutrient dense diets. product is heated during drying, availability of Periodically, grades unfit for oil extraction are essential amino acids such as lysine is often 10 available for animal feeding. Canola seed suffers to a 20% below expected values. Alfalfa is from the same problems as described for canola very high in fiber content, and is most often added meal, although obviously most harmful elements to poultry diets as a source of xanthophylls for are diluted by the high oil content. Seeds must be pigmentation, or as a source of so-called ground adequately to ensure normal digestion, and unidentified growth factors. this is best accomplished by mixing with ground corn prior to passing through a hammer mill. Alfalfa products should contain a minimum The oil provides considerable energy, and is an excel- of 200,000 IU vitamin A activity per kg, although lent source of linoleic acid. The ground seed is not in most cases this will only be 70% available. In too oily, and so provides a practical way of adding order to achieve intense yellow skin color in considerable quantities of fat to a diet. Due to early broilers or egg yolk color of 10 on the Roche frost damage, some samples of canola contain oil scale, diets should contain 5% alfalfa as one source that is contaminated with chlorophyll – while unac- of xanthophylls in the diet. Alfalfa levels much ceptable to the human food industry, this contaminant in excess of 5% have only a moderate effect on does not seem to pose any major problems to poultry. pigmentation and so other natural or synthetic sources must be used to ensure consistently 26. Groundnut (Peanut) Meal high levels of pigmentation. At high levels of inclusion (20%) problems can arise due to the The peanut is an underground legume, and saponins and phenolic acids normally present because of warm moist conditions in the soil, is in alfalfa. If alfalfa contains any appreciable mold very susceptible to fungal growth with aspergillus count, then estrogen level can be high. Fresh grass contamination being of most concern. Grown is thought by some nutritionists to contain an essentially for their oil, peanuts yield a solvent unidentified growth factor which is of particular extracted meal containing 0.5 – 1% fat with about significance to turkeys, although much of this 47% protein. As with soybeans, peanuts con- factor is destroyed by the dehydrating process. tain a trypsin inhibitor that is destroyed by the Even so, many nutritionists still insist on adding heating imposed during oil extraction. Potential 1 – 2% dehydrated alfalfa to turkey feeds, aflatoxin contamination is the major problem with especially pre-starter and starter diets. The groundnut meal. Being a potent carcinogen, addition of small quantities of alfalfa also impart aflatoxin causes rapid destruction of the liver, even a darker color to diets which helps mask any minor at moderate levels of inclusion. Peanut meal that fluctuations in appearance due to regular changes is contaminated with aflatoxin can be treated by in formulations. The quality of alfalfa products ammoniation which seems to remove up to has been improved considerably in recent years 95% of the toxin. Alternatively, products such due to the use of inert gas storage, pelleting and as sodium-calcium aluminosilicates can be addition of antioxidants. added to the diet containing contaminated groundnut because these minerals bind with afla- toxin preventing its absorption. SECTION 2.1 Description of ingredients

68 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION 27. Peas in formulating lysine-deficient diets for experi- mental reasons. Sesame also contains high Peas are a medium energy-protein ingredient levels of phytic acid which can cause problems that can be used effectively in poultry diets with calcium metabolism leading to skeletal depending upon local economical conditions. disorders or poor eggshell quality. If diets The major limitation to using peas is low levels contain >10% sesame, then the diet should be of sulfur amino acids and moderate energy formulated to contain an extra 0.2% calcium. level. With high-tannin peas, there may be an advantage to some type of heat treatment, 30. Lupins although such processing is of little value for regular pea varieties. Protein digestibility is Low alkaloid lupins are being increasingly reduced by about 6% for each 1% increase in used as an alternative feedstuff for poultry in tannin content. Peas do have some of their certain areas of the world. These new cultivars have carbohydrate as oligosaccharides, and so enzyme been reported to contain low levels of the toxic alka- systems being developed to improve the digestibil- loids (less than .01%) normally found in wild vari- ity of soybean meal may be of use with peas. eties. These low alkaloid lupin seeds are often referred Peameal is a very dense material and bulk to as sweet lupins and can vary in seed color. density of the final diet should be taken into The high level of fiber in the seeds (up to 25%) results consideration for diets containing > 15% peas. in low metabolizable energy values compared to soybean meal. Mature lupin seeds contain little or 28. Safflower no starch, the bulk of their carbohydrate being oligosaccharides (sugars) and non-starch poly- Safflower is grown mainly for its oil content saccharides. Many reports suggest that sweet which, although variable, can be as high as lupins are comparable to soybeans in terms of pro- 40%. The residual meal contains in excess of 20% tein quality although they are much lower in fiber and is referred to as undecorticated safflower methionine and lysine. Their low oil content (6 to meal. It is possible to commercially remove a 10%) and absence of antinutritive factors means that large portion of the hull resulting in a meal they can be inexpensively processed. Recent containing 42 to 44% protein with a fiber studies have shown that dehulling lupins results in content of around 14%. This product is referred a marked increase in nutritive value. Also with prop- to as decorticated meal. Safflower meal is very er dietary enzyme supplement the feeding value of deficient in lysine, although with appropriate lysine raw lupins is improved. Fine grinding also aids supplementation the protein quality of safflower digestibility. meal is similar to that of soybean meal. However, with the high fiber content the available energy 31. Blood Meal is still relatively low and so its value does not equal that of soybean meal. Where safflower meal is Blood meal is very high in crude protein, and available, relatively large quantities can be used while it is an excellent source of lysine, it is very in poultry diets if proper consideration is given deficient in isoleucine and this imbalance needs to nutrient availability. correcting if any substantial quantity is used in a diet. Blood meal is essentially the solids of the 29. Sesame Meal blood from processing plants, and consists mainly of hemoglobin, cell membranes, cellu- Sesame meal is very deficient in available lar electrolytes and a small quantity of lipid. lysine, and this is sometimes used to advantage SECTION 2.1 Description of ingredients

CHAPTER 2 69 INGREDIENT EVALUATION AND DIET FORMULATION Historically, the level of blood meal used in than limestone, but it offers the advantage of being diets has been severely limited, mainly because clearly visible in the diet to the egg producer and of problems of palatability, poor growth rate so there is less chance of omission during feed and abnormal feathering. All these problems relate manufacture. Birds also have some opportunity to inherent amino acid balance and also to low at diet self-selection if oyster shell is given, and digestibility induced by overheating of the blood this may be of importance in maintaining during processing. With less harsh drying optimum calcium balance on egg-forming vs non treatments, the amino acids are more stable, and egg-forming days. There are current limitations there are few problems with palatability. If on oystershell dredging in the Chesapeake blood meal is overheated, it has a much region of the U.S.A., due to environmental darker color, tending to be black rather than issues, and this may add to the discrepency in reddish-brown. The amino acid balance of price between oystershell and limestone. blood meal can be ‘improved’ by combining it with other ingredients. For example, a 50:50 Limestone should be in as large a particle size mixture of blood meal and hydrolyzed hair as can be readily manipulated by the bird’s meal gives a product with a reasonable amino beak. For laying hens, this means a fairly coarse acid balance, and certainly a balance that is crumble consistency. There has been some preferable to either product alone. Such a concern in recent years regarding the variabil- mixture may be used in least-cost formulation, ity in solubility of limestone from various sources. whereas either ingredient is unlikely to be used This can easily be checked by measuring pH independently because of amino acid balance. changes when limestone is added to hydro - chloric acid at initial pH of 4.0. Obviously 32. Sources of Calcium, 100% solubility is desirable, yet ideally this Phosphorus and Sodium should be achieved over a prolonged period of time which hopefully correlates with the slow Calcium release of calcium into the blood stream. Constraints are not usually imposed on these Periodically, dolomitic limestone is offered ingredients because there should be fairly to the feed industry. Dolomitic limestone stringent constraints imposed on minimum and contains at least 10% magnesium, and this com- maximum levels of calcium and phosphorus in plexes with calcium or competes with a diet. There has been considerable controversy calcium for absorption sites. The consequence of in the past concerning the relative potency of feeding dolomitic limestone is induced limestone vs oyster shell as sources of calcium, calcium deficiency, usually manifested by poor skele- especially for the laying hen. Perhaps of more tal growth or egg shell quality. The major user of importance than the source of calcium, is dolomitic limestone is the steel industry and so prob- particle size. Usually the larger the particle lems with this ingredient seem to mirror the eco- size, the longer the particle will be retained in nomic malaise in steel production. Dolomitic lime- the upper digestive tract. This means that the stone should never be used in poultry diets. larger particles of calcium are released more slowly, and this may be important for the Phosphorus continuity of shell formation, especially in the dark period when birds are reluctant to eat. A considerable number of inorganic Oyster shell is a much more expensive ingredient phosphorus sources are used around the world. SECTION 2.1 Description of ingredients

70 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Most naturally occurring phosphate sources are friction at the pellet die. With phosphates, unavailable to the bird unless they are heat- there is a distinct advantage to using rock treated during processing. As with limestone, the phosphates rather than mono- or dicalcium solubility in HCl at pH 4 can be used as a meas- phosphate in terms of pelleting efficiency, where ure of quality. Insoluble phosphate sources are up to +10% throughput is achieved. unlikely to be available to the bird – however solubility is not a guarantee of subse- Sodium Sources quent availability. Solubility tests are therefore only useful in screening out insoluble sources. Tests Most diets will contain some added salt, for biological availability are much more com- usually in the form of sodium chloride. Where plex, because they necessarily require a chick bioas- iodine is not added as a separate ingredient, iodized say where growth and bone ash are measured. salt must be used. In most countries the various salt forms are differentiated by color, with The phosphorus in most phosphate sources common salt being a natural white color and with the exception of soft phosphate, can be iodized salt being red. Cobalt iodized salt is often regarded as close to 100% available. Rock used in diets for swine and ruminants, and this phosphate and Curaco phosphate are the major can be used without any problems for poultry. exceptions because these sources may only be This type of salt is usually colored blue. Because 60 – 65% available to the bird. Anhydrous high levels of sodium chloride can lead to dicalcium phosphate is about 10% less available increased water intake, then a substitution of than the hydrated form, and this seems to relate sodium bicarbonate for a portion of this chloride to solubility. In this context, ingredients that salt has been shown to be beneficial. Under these stimulate gastric secretion, and hence HCl condition, up to 30% of the supplemental salt production, seem to result in improved utiliza- can be substituted with sodium bicarbonate tion of the anhydrous form. Some rock phosphates without loss in performance, and such birds contain various contaminants of concern for often produce drier manure. For substitutions of poultry. The most common of these is vanadium. sodium bicarbonate for sodium chloride above At just 7 – 10 ppm of the diet, vanadium will cause 30%, care must be taken to balance dietary loss in internal egg quality and hatchability. At chloride levels, since under commercial conditions slightly higher levels (15 – 20 ppm), there is a it is often difficult to add inexpensive sources of change in the shell structure where the shell takes chloride other than salt. Chloride contributed on a somewhat translucent appearance, and by ingredients such as choline chloride and appears more brittle. Rock phosphates can lysine-HCl should be accommodated during also contain as much as 1.5% fluorine. Because formulation. There is a trade-off when substituting fluorine can influence calcium metabolism, sodium bicarbonate for sodium chloride under there are often regulations governing the heat-stress conditions. Birds will drink less maximum permissible levels in feed. Only de- when NaHCO3 is used, and this is the reason fluorinated rock phosphates are recommended for substitution. However, we really have to although it must be remembered that this question this scenario, since higher levels of water product usually contains about 5% sodium. intake are correlated with survival under extreme Most mineral sources are detrimental to the heat stress conditions. Sources of calcium, pelleting process because they create significant phosphorus and sodium are given in Table 2.13. SECTION 2.1 Description of ingredients

CHAPTER 2 71 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.13 Calcium, phosphorus and sodium sources Ingredient % Ca %P Limestone 38.0 - Oyster shell 38.0 - Calcium carbonate 40.0 - Bone meal 26.0 Monocalcium phosphate 17.0 13.0 Dicalcium phosphate 21.0 25.0 Tricalcium phosphate 23.0 20.0 Defluorinated rock phosphate 34.0 19.0 Curaco phosphate 35.0 19.0 Phosphoric acid (75%) 16.0 - 25.0 Ingredient % Na % Cl Plain salt 39.0 60.0 Iodized salt 39.0 60.0 (I, 70 mg/kg) Cobalt iodized salt 39.0 60.0 (I, 70 mg/kg; Co, 40 mg/kg) Sodium bicarbonate 27.0 - 33. Trace Minerals contain ‘bound’ water which obviously dilutes the effective mineral concentration. For Trace minerals are available in a variety of example, hydrated cupric sulphate (white forms, and periodically problems arise due to lack crystal) contains about 40% copper, whereas the of knowledge of the composition, and/or stability more common pentahydrate (blue) contains of mineral salts. Most research into mineral 26% copper. It should also be emphasized availability has been conducted with so-called that the various processing conditions used in reagent-grade forms of minerals, which are very manufacturing will likely influence mineral pure and of known composition and purity. bioavailability. A combination of these two Unfortunately, the feed industry cannot afford the factors can mean a substantially lower potency luxury of such purity, and so obviously, feed grade of trace mineral sources relative to chemical stan- forms are used. dard values (Table 2.14). For this reason, feed manufacturers are encouraged to take great One of the most important factors to ascertain prior to formulation is the state of hydration of a mineral. Many mineral forms SECTION 2.1 Description of ingredients

72 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.14 Trace mineral sources Cobalt Ingredient % of Manganese Ingredient % of Copper major major Iron oxide mineral Zinc oxide mineral Magnesium chloride 71.0 Selenium chloride 77.0 sulphate 24.0 Iodine sulphate 27.5 carbonate 21.0 carbonate 32.5 oxide1 46.0 oxide 47.0 chloride 79.0 chloride 78.0 sulphate 37.0 sulphate 48.0 carbonate 25.5 carbonate 36.0 oxide2 55.0 sodium selenite 52.0 chloride3 77.0 sodium selenate 46.0 sulphate2 34.0 potassium iodine 42.0 carbonate2 32.0 calcium iodate 77.0 oxide 40.0 65.0 carbonate 56.0 30.0 care in ordering trace minerals based on valency, 1 Cupric; 2 Ferrous; 3 Ferric hydration and purity. All minerals sources should be analyzed, on an ‘as is’ basis for the major Cobalt mineral component. The major source of cobalt is cobalt sulphate Because feed manufacturers are often or cobalt carbonate. Both products are good concerned about ‘space’ in the diet during sources of cobalt, with the cobalt as sulphate being formulation, there is a trend towards making slightly more available than in the carbonate very concentrated mineral and vitamin form. Cobalt oxide has very low availability, premixes. In considering concentration of min- and should not usually be considered during eral sources, oxides appear attractive, since they formulation. invariably contain the highest mineral concen- tration. Oxides however, are potent oxidizing Copper agents, and if stored with premixed vitamins for any length of time, can cause the destruction Copper oxide, sulphate and carbonate are used of vitamins that are susceptible to oxidation. by the feed industry. Copper oxide can be of very Since oxides are generally less available than other low biological availability, especially with poor mineral salts, they should not be used exclusively quality samples that contain significant amounts in mineral premixes. of metallic copper. Good quality copper oxide can be considered as available as is copper sulphate. As previously mentioned, the degree of hydration of copper sulphate must be specified. SECTION 2.1 Description of ingredients

CHAPTER 2 73 INGREDIENT EVALUATION AND DIET FORMULATION Iron aluminum, lead and cadmium. If good quality sources are considered, then zinc oxide and zinc sulphate Ferrous salts should be used in feed manu- appear to be of comparable biological availability. facture. As with copper, the major contaminant can be the metal itself, and this has a very low Selenium biological availability. Ferrous carbonate and fer- rous sulphate are the preferred forms of iron. Selenium is most often added to feeds as Ferrous salts are prone to chemical change dur- sodium selenite or sodium selenate. The most ing storage, such that 10 – 20% of ferric salts can common naturally occurring form of selenium be produced from original ferrous forms after 3 is selenomethionine, and this seems to have a much –6 months storage at around 25ºC. lower potency than either of the salt forms. There seems to be a greater availability of Magnesium selenium within low protein diets, although this may be related to the fact that when birds Magnesium carbonate and oxide are both are growing at a slower rate, their absolute available in feed grade form. The oxide can take selenium requirement is reduced. Selenium up both water and carbon dioxide when stored availability, from whatever source, is improved for any length of time, and such activity obviously when diets contain antioxidants. reduces the relative potency of magnesium. Selenite is more readily reduced to elemental Manganese selenium, and for this reason selenate is some- times preferred. Selenium metal is less available The major source of manganese used in the and can form insoluble complexes with other feed industry is manganese oxide. Sulphate minerals. Whichever form of selenium is used, and carbonate sources both have higher biological it must be remembered that the final diet inclusions availability, yet these are usually uneconomical are extremely low in relation to the other to use. Manganese oxide has a biological minerals, and so some degree of premixing is availability of 50 – 70%, yet this can be greatly essential prior to incorporation in diets or premixes. influenced by its major contaminant, namely manganese dioxide. Manganese dioxide is Iodine only 50% as bioavailable as is the oxide, and so an appreciable content of dioxide can lead to a If iodine is added to a mineral premix, rather marked reduction in effectiveness of manganese than supplied with salt, then potassium iodide oxide. Oxides should not contain more than 10% and calcium iodate are the preferred sources. dioxides, and undoubtedly the range of availability Potassium iodide is very unstable and deterio- quoted in research findings is usually a rates rapidly with moderate exposure to heat, light reflection of dioxide contamination. and/or moisture. Calcium iodate is the most common source of supplemental iodine. Zinc Mineral chelates Zinc oxide and zinc sulphate are the most common forms of zinc used in the feed Chelates are mixtures of mineral elements industry. Zinc is often used as a catalyst in bonded to some type of carrier such as an various industrial processes, and unfortunately cat- amino acid or polysaccharide. These carriers, alysts sometimes find their way into the feed or ligands, have the ability to bind the metal, industry and are of low biological availability. Zinc sources can be contaminated with SECTION 2.1 Description of ingredients

74 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION usually by covalent bonding through amino inorganic salts. There are also claims of chelated groups or oxygen. The formed chelate is usually minerals being used more effectively at the a ring structure with the divalent or multivalent cellular level following absorption. There are few metal held strongly or weakly through two or more classical supporting claims for these suppositions, covalent bonds. Iron in hemoglobin is the and so enhanced performance of meat birds and classical example of a chelate. The covalent bond- layers is discussed in terms of stimulation of ing is such that the chelate has no electrical charge. various biological processes by the mineral and/or that the chelated mineral enters certain Chelated, or complexed minerals are usually pools with greater affinity or efficiency. much more expensive than inorganic minerals, and so one expects improved bird perform- Inorganic minerals are likely to contain trace ance through either enhanced absorption or quantities of heavy metals such as arsenic, lead better utilization in some way. It is difficult to and cadmium. Such levels of heavy metals are rationalize the cost of chelated minerals based not problematic to poultry, although the EEC has solely on improved absorption in the intestine. recently imposed limits of these metals in Even a 50% difference in absorption can be most mineral premixes and complete feeds. While it economically resolved by doubling the level of is challenging to consistently achieve minimum inorganic mineral used. However, there are levels using conventional mineral salts, most chelat- limits to the level of any one mineral to be ed minerals are very pure and usually contain used, because of potential negative effects of no heavy metals. absorption and utilization of other minerals and other nutrients. The mineral availability from Ultimately the choice of using inorganic some inorganic sources can be very low. For exam- versus chelated minerals is one of economics, ple, the manganese in some samples of manganese which obviously relates to cost benefit. Such results sulfate has been reported at just 5%, and in may vary depending upon the levels and this instance a 20 fold increase in inclusion spectrum of trace minerals used and the bioavail- level, while correcting the potential manganese ability to be expected from inorganic sources that absorption problem, will likely have adverse effects are available. on utilization of phosphorus, calcium and iron. 34. Synthetic Amino Acids Factors affecting the uptake of heme iron are often used to support the concept of using Synthetic sources of methionine and lysine chelated minerals. There are a number of other are now used routinely in poultry diets and trace minerals, such as copper, manganese and tryptophan and threonine will likely be used phosphorus that can affect absorption of inorganic more frequently as future prices decline. In iron, while uptake of heme iron will be little most situations, the use of synthetic amino acids affected. The uptake of chelated minerals is there- (Table 2.15) is an economic decision, and so their fore expected to be more consistent and less price tends to shadow that of soybean meal, affected by adverse (or enhanced) environments which is the major protein (amino acid) source in the gut lumen. Bioavailability of minerals from used world-wide. By the year 2010, lysine use chelates should also be consistent because of in North America is estimated to be at 150,000 standardization during manufacture versus less tonnes while that for methionine will be around standard conditions with some supplies of 85,000 tonnes, of which the poultry industries use 30 – 65%. SECTION 2.1 Description of ingredients

CHAPTER 2 75 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.15 Synthetic amino acids Amino acid Relative Crude protein DL-Methionine activity equivalent Methionine hydroxy analogue (liquid) (%) L-Lysine L-Lysine HCL 100 59 L-Arginine L-Arginine HCL 88 0 L-Tryptophan L-Threonine 100 120 Glycine Glutamic acid 79 96 100 200 83 166 100 86 100 74 100 117 100 117 Lysine is usually produced as the hydrochlo- greater synthetic tryptophan use comes from the ride salt, and consequently, the commercial swine industry. Tryptophan will become a products have 79% lysine activity on a weight limiting nutrient as crude protein levels of diets basis. Liquid lysine products are now also avail- are reduced, although currently its efficient use able. In North America, lysine tends to be con- is somewhat hampered by complexity involved sidered a commodity, and as such its use is in diet analysis. Tryptophan levels in ingredients directly related to that of other ingredients. In and feed are much more difficult to assay than general, there is greater L-lysine HCl usage are the other common amino acids, and in when soybean meal price increases, or when corn part, this situation leads to variability in research price declines. In Europe however, because of results aimed at quantitating response to tryptophan. inherently higher commodity prices, L-lysine HCl This amino acid is most likely to be considered tends to be used less as a commodity, and more when diets contain appreciable quantities of meat as a means of improving performance. Care must or poultry by-product meal. be taken therefore, in interpretation of cost benefit of lysine use in research results reported Methionine is available in a number of forms from these two regions. and also as an analogue. Over the years there has been considerable research into the potency and Tryptophan is not usually a limiting amino use of these various sources. There are essentially acid in most poultry diets, and so the move to four different sources of methionine (Table 2.16). SECTION 2.1 Description of ingredients

76 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.16 Methionine sources DL- Methionine Methionine DL- methionine hydroxy hydroxy methionine Na analogue analogue- Ca CH3 CH3 CH3 CH3 S S S S CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 H-C-NH2 H-C-OH H-C-OH H-C-NH2 COONa+ COOH COOCa+ COOH Liquid Liquid Powder Powder Dow Chemical was the first to produce pow- liquid MHA (eg. Alimet®) often arises in selec- dered DL-methionine in commercial quantities tion of methionine sources. Liquid MHA has a in the 1940’s, while Monsanto introduced the value of 88% methionine based on normal calcium salt of methionine hydroxy analogue in the chemical structure. Availability of this 88% 1950’s. Since this time, the market has established value has then been shown to vary from 60 – demand for both DL-methionine and the analogue, 100%. It seems inconceivable that any nutrient in both powdered and liquid forms. could have such variable efficacy, and so one must look at experimental conditions and diet for- It has been known for some time that most mulation in assessing such results. Potency of essential amino acids can be replaced by the MHA relates to variable uptake in the intes- corresponding -keto acid (analogue). With the tine, degradation in body tissues and/or degree exception of lysine and threonine, which are not of elimination by the kidney. Another major vari- involved in transamination processes, it is able in response to MHA under commercial therefore possible to replace amino acids with conditions is ingredient methionine levels used their keto acid-analogues. Presumably the bird in formulation and diet specifications for methio- produces the corresponding amino acid by nine and cystine. There are usually logical reasons transamination involving mainly non-essential why nutritionists use different potency values. The amino acids such as glutamic acid. Such bottom line is cost per kg of meat/eggs produced, transamination can occur in various tissues, and the value of products such as MHA quick- and some bacteria in the intestine may also ly establish themselves over time within an synthesize amino acids prior to absorption. The integrated operation. In most situations MHA is question of relative potency of products such as used at 85-88% relative to DL-methionine. SECTION 2.1 Description of ingredients

CHAPTER 2 77 INGREDIENT EVALUATION AND DIET FORMULATION 2.2 INGREDIENT TESTING tests are specific to certain ingredients and to spe- cific nutrients and/or antinutrients within an I ngredients must be continuously moni- ingredient. Alternatively, some tests are more gener- tored to ensure consistency of nutrient ic and can be applied across a number of ingre- profile and presence of potential contam- dients. The decision to carry out any of these tests inants. The number and frequency of assays will is based on significance of the ingredient in depend upon the class of ingredient, historical the diet, and so the relative contribution of con- results of analysis and to some extent the season stituents under test. Developing historical data of the year. Ingredients from new suppliers on ingredients is also a useful way of deter- should be tested the most rigorously, and mining the need and frequency of number and frequency of testing reduced only various testing procedures. The following tests when consistency of nutrient profile is established. or methodologies are assumed to be in addition Examples of the type and frequency of testing are to more extensive chemical testing that will given previously with the description of all the routinely be used for the most important nutrients. major ingredients. a. Bulk density The frequency of sampling will obviously vary with the significance of a particular ingredient Bulk density of individual cereals is correlated in the feed. For example, where fish meal is used with energy value and protein content. In North extensively, and represents a significant pro- America, the usual measurement is bushel portion of dietary amino acids, then amino acid weight, while the common metric equivalent is analyses may be done more frequently, and it may kg/hl. Weight of 100 kernels of cereal is also used also be advisable to screen more often for as an indicator of bulk density. Under normal gizzard erosion factors. On the other hand, where growing conditions, as bulk density declines, there a history of consistent analyses is developed, then is usually a reduction in energy level, mainly testing can be less frequent. associated with reduction in starch content of the endosperm. Concurrently protein content often For assay results to be meaningful, ingredients increases since protein is commonly found in the must be sampled accurately. For bagged ingre- outer bran or pericarp layers. Bulk density is also dients, at least 4 bags per tonne, to a maximum a useful measure for calculation of needs for of 20 samples per delivery, should be taken, and storage space within the mill. then these sub-samples pooled to give one or two samples that are sent for assay. It is always Bulk density will vary with moisture content, advisable to retain a portion of this mixed sample, and this should be taken into account during especially when assays are conducted by outside measurement. Density is easily measured by laboratories. For bulk ingredients, there should weighing the cereal or feed into a container of be about 10 sub-samples taken from each truck known volume. The smaller the container, the or rail car load and again this mixed to give a greater the care needed in standardizing the representative composite for assay. filling and especially the packing of the ingredient. Bulk density values are not always There are a number of rapid tests available for evaluating ingredients. In some instances, these SECTION 2.2 Ingredient testing

78 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION additive and so the density of a mash feed pared for their nutrient content on a dry matter basis. cannot always be predicted from knowledge of Moisture much in excess of 12 – 13% is cause for bulk density of component ingredients. This concern regarding potential for mold growth. situation arises, because of ‘mixing’ of particles of different size within a feed, so affecting the Fat is determined by extracting the dry empty space common with low bulk density sample with ether. The weight of the extract is ingredients such as wheat shorts or alfalfa meal. determined after distilling the ether and weigh- ing the residue. Although this is the usual b. Proximate analysis method for determining fat in feeds, ether extraction does not remove all the fats, especially Proximate analysis is still the most widely used phospholipids or fats bound to protein. Often acid system for monitoring the quality of ingredi- hydrolysis followed by extraction of the hydrolysate ents. At a time when we formulate diets based with chloroform:methanol or ether is necessary on digestible or metabolizable nutrients, its to obtain ‘total’ lipid values. Acid hydrolysis also value is often questioned, since proximate com- liberates fat present as soap, and is more likely ponents are very broad and encompass what can to liberate fat from bacterial cell walls. be both digestible and indigestible components. However, proximate analysis is quite rapid and Crude protein is determined by measuring the inexpensive, and does give an idea of continu- nitrogen content of the feed and multiplying this ity of composition. Proximate analyses can by 6.25. This factor is based upon the fact that on also be used to predict the content of nutrients average, a pure protein contains 16% nitrogen. such as total and digestible amino acids. This type Thus 100/16 = 6.25. For most ingredients, this of information is essentially regression analyses assumption is fairly accurate, and allows us to esti- of simple proximate components versus analytical mate protein (which is a very complex assay) based values for amino acids. simply on assay for nitrogen, which is quite straightforward and inexpensive. The nitrogen con- For proximate analysis an ingredient is tent of a feedstuff is determined usually by the partitioned into six fractions, namely water, Kjeldahl or heco methods. The Kjeldahl involves ether extract, crude fiber, nitrogen-free extract, conversion of the nitrogen in feedstuffs to an crude protein and ash. Some of the information ammonium salt by digestion with concentrated from proximate analyses (usually the protein, ether sulfuric acid in the presence of a suitable catalyst. extract, fiber and ash values) are shown on The ammonia is distilled from the digestion mix- descriptive feed labels, which accompany feed- ture into a collecting vessel after the sample is made stuffs and complete feeds. These values alkaline. The amount of ammonia is determined represent the guarantees of quality used by the by titration with standard acid, and then nitrogen, feed manufacturing industry. and hence crude protein are calculated. Water is usually determined by the loss in weight Ashing of an ingredient combusts all organic that occurs in a sample upon drying to constant constituents, leaving behind only the mineral weight in an oven. Although water is considered elements. Some elements such as selenium a nutrient, it effectively is a diluent for other and arsenic form volatile oxides at this temper- nutrients. Increase in moisture, therefore, reduces ature. These losses can be avoided if the ash is the total nutritional value of a feedstuff. Because made alkaline by addition of known quantities water content can vary, ingredients should be com- of calcium oxide prior to ashing. SECTION 2.2 Ingredient testing

CHAPTER 2 79 INGREDIENT EVALUATION AND DIET FORMULATION Crude fiber refers to the organic residue of Proximate analyses should perhaps be better a feed that is insoluble after successive boiling termed ‘approximate analyses’, especially since its with H2SO4 and NaOH solutions according to main component, NFE, is determined by specified procedures. The determination of difference. However, it is a useful starting point for crude fiber is an attempt to separate the more necessity to conduct other more specific analyses. readily digestible carbohydrates from those less readily digestible. Boiling with dilute acid and c. Amino acid analyses alkali is an attempt to imitate the process that occurs in the digestive tract. This procedure is based on Determination of total amino acids is time the supposition that carbohydrates, which are consuming and expensive and so tends not to be readily dissolved by this procedure, also will be read- a routine procedure. The most common procedure ily digested by animals, and that those not soluble today is gas-liquid chromatography, which can under these conditions are not readily digested. At be highly automated to give relatively speedy best, this is an approximation of the indigestible mate- analyses. However, the major time factor resides rial in feedstuffs. Nevertheless, it is used as a gen- in preparation of the sample for analysis, since the eral indicator in estimating the energy value of feeds. component amino acids have to be freed from with- Feeds high in fiber will be low in ME. in protein structures. This pre-analysis procedure is usually termed hydrolysis, and unfortunately Nitrogen-free extract (NFE) is determined by care must be taken during this process, since two subtracting from 100 the sum of the percentages important amino acids can be destroyed by inap- of ash, crude protein, crude fiber, ether extract propriate processing. Tryptophan is almost com- and water. The NFE is considered to be a measure pletely destroyed by acid hydrolysis and can only of the digestible carbohydrates. A criticism of the be determined following alkaline or enzymatic proximate analysis system, is that its major hydrolysis. The acid buffers used in amino acid contributor, namely NFE, is calculated by difference, analyses also cause loss of tryptophan. Special pre- and not actually determined directly. cautions also must be taken against loss of methio- nine and cystine during hydrolysis. Perfomic Proximate analysis gives some indication acid oxidation is usually carried out prior to of the nutritive value of an ingredient. For hydrolysis, such that methionine is converted to example, a material very high in crude fiber is methionine sulfone and cystine to cysteic acid. likely to have a low energy value, while feedstuffs Amino acids are then liberated from the proteins low in crude fiber and high in ether extract are by hydrolysis with HCl. In the case of tryptophan, likely to be of high energy value. The crude pro- further precautions against destruction by acids and tein content of material is a good indicator of its alkalis are essential. Such problems in prepara- potential value as a protein source. Unless the tion of samples are often the reason that tryptophan amino acid composition is known, however, the is omitted from published data. actual quality of the protein cannot be determined. Certain ingredients such as meat meal normally For measurement of digestible (available) contain a high quantity of ash. In meat meal and amino acids, it is necessary to feed birds and meas- fish meal, calcium and phosphorus may be ure total amino acids in the feed and excreta. The estimated from the ash value since it consists main- difference between amino acid input and ly of bone ash. Thus a determination of the ash output is assumed to be digestible or available of these materials may be very useful. amino acids. The bioassay is most easily achieved SECTION 2.2 Ingredient testing

80 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION by the TME precision force-feeding system, Because of the complexity and cost involved because the ingredient can be considered alone. in measuring AME or TME, various chemical or in In a classical bioassay, the bird voluntarily eats vitro systems have been developed. Essentially these feed and only the test ingredient can supply amino methods attempt to correlate more easily measurable acids. This situation means that semi-purified diets components, with available energy. One of the first (containing other basal ingredients such as such calculations was applied by Carpenter and sugar, starch, sand and oils) are necessarily Clegg (1956) and their equation is still as good as used and the practicality of such diets are often anything developed in the last 50 years. questioned. Today, virtually all estimates of amino acid digestion are derived from the force- ME (kcal/kg) = 53 + 38(%CP + 2.25 x % fat feeding method, and values are often termed TAAA + 1.1 x % starch + % sugar) (True Amino Acid Availability). This type of prediction equation is accurate to d. Metabolizable Energy within ± 200 kcal/kg and so is useful for giving an (AME or TME) estimate of AME for a novel ingredient. There have also been ME assays based on enzyme digestion. The Metabolizable energy is the most costly most successful uses duodenal fluid taken from a pig, nutrient in an ingredient or diet, yet unfortunate- and measuring the gross energy of solubilized ly it is the most difficult to measure. As for components after 1 – 2 hr of incubation. AME has digestible amino acids, estimates of AME or TME also been predicted by NIRA (see next section). require a bioassay involving live animals. The only lab assay for energy is gross energy and this e. Near Infra Red Analysis is merely a starting point used in AME or TME (NIRA) determinations. Gross energy is the total heat evolved when an ingredient or diet is burned in an NIRA offers the possibility for very rapid atmosphere of oxygen. Wood and corn have analyses of ingredients and feeds. The technique approximately the same gross energy. has the potential to assay many organic com- pounds. The system has the capability to measure In an energy bioassay, birds are fed diets metabolizable energy as well as more simple containing a given quantity of the ingredient, and components such as fat, moisture, protein and feed intake and excreta output measured over a fiber. Analysis relies on measuring how much 3–5 d balance period. Gross energy is determined light energy is absorbed when the sample is on feed and dried excreta and calculations made bombarded with light at very specific wavelengths. to determine the metabolizable energy derived from the ingredient under test. In theTME assay, the bird The basis of NIRA is chemometrics, which is force-fed only the ingredient under test, and so is the application of mathematics to analytical the estimate of ME is simplified. With all the chemistry. The technique is an integration of laboratory and sample preparation necessary for spectroscopy, statistics, and computer sciences. the test, it is challenging to generate results Mathematical models are constructed that relate within a 2–3 week period, at a cost approaching chemical composition (active chemical groups) $1,000 USD per sample. to energy changes in the near infra red region of the spectrum which ranges from 700 to 2500 nm in wavelength. In this region of the spectrum we SECTION 2.2 Ingredient testing

CHAPTER 2 81 INGREDIENT EVALUATION AND DIET FORMULATION measure mainly vibrations of chemical bonds in of correlation coefficients at each wavelength and which hydrogen is attached to atoms such as nitro- simultaneously selecting both the best fit with the gen, oxygen, or carbon. Because most feedstuffs nutrient under study, and also the best fit at all other are opaque, NIRA uses reflectance instead of absorption frequencies so as to remove all interference transmittance. The reflected light of a sample is problems with application of a correction factor. used to indirectly quantify the amount of energy absorbed in a sample. NIRA measures the The usefulness of NIRA, therefore depends absorption of infra red radiation by various entirely on the careful and conscientious calibration components, for example, peptide bonds at of the equipment. To some extent this exercise specific wavelengths in the near infra red spectrum. has been simplified through introduction of Other components of the sample absorb energy so-called scanning machines that cover a wide as well, however, and have the effect of interfer- band of NIR. Prior to this technology, only fixed ing. This effect is eliminated by mathematical treat- wavelength equipment was available, and so ment of the spectral data and by multiple linear prior knowledge of likely absorption bands or regression or other statistical procedures. tedious testing of numerous wavelengths was essential in order to develop useful calibrations. Because each molecule usually exists in its low- est energy state, absorption of energy will raise its Developing calibrations for components energy state to some degree. Such energy absorp- such as moisture, fat, crude protein and fiber is tion occurs at a wavelength that is characteristic for a very straightforward procedure. These calibrations that particular molecule. Energy absorption in the can be combined within a single program such fundamental infra red region is very strong, but also that from each ingredient scan, these various very specific for certain molecular groups. For exam- analyses are conducted concurrently. For most ple, water has a characteristic absorption at the same commercial machines, ensuring consistent fine- wavelength as does starch. Strong, but specific ness of grind and controlling moisture content fundamental wavelengths, would be difficult to dif- of samples eliminates much of the variation ferentiate for these two components. This does not associated with operating procedure. mean to say that infra red analysis does not have a place in feed analysis. For example, with pure Determination of ME with NIRA provides a nutrients (amino acids, vitamins) the use of light considerable challenge. Firstly, there is a need reflectance in the fundamental range may offer poten- for an extensive range of diets of determined analy- tial for very specific analysis of purity. With sam- sis to be used for calibration. The conventional ples of mixed composition, whether it be ingredients bioassay for ME is both time consuming and very or complete feeds, then a more subtle analysis must expensive, and these facts have undoubtedly be used to differentiate all the various chemical group- limited investigation to date. Secondly, ME per ings. In the weaker absorbing NIR range of wave- se provides a complex problem for NIRA, lengths, it is secondary absorption wavelengths that because energy contribution is not confined to are considered – these are most often referred to one nutrient but rather is represented by a range as ‘overtones’. By considering a spectrum of of molecular bondings and configurations. wavelengths, a characteristic pattern of absorption Usefulness of NIRA to predict ME therefore energy is given for each major component of the depends upon careful bioassay of a range of diets sample. Chemometrics then involves calculation preselected in terms of anticipated ME, nutrient SECTION 2.2 Ingredient testing

82 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION contribution and ingredient composition. These of such predictions is greatly influenced by latter parameters are of importance if ‘universal’ the time and precision involved in calibration using calibrations are to be developed. Similarly, samples of known composition. great care must be taken in the mathematical manipulation of spectral coefficients. Over the f. Urease testing of soybeans and last few years Valdes and Leeson (1992, 1994) soybean meal have developed a number of such calibrations for feeds and ingredients. Table 2.17 shows some Levels of the enzyme urease are used as an of these results for ingredients. indicator of trypsin inhibitor activity. Urease is much easier to measure than is trypsin inhibitor Table 2.17 Prediction of metaboliz- and both molecules show similar characteristics able energy by NIRA (kcal/kg) of heat sensitivity. A rapid qualitative screening test for urease can be carried out using Ingredient Determined NIRA conversion of urea to ammonia in the presence prediction of an indicator. Corn 3380 Barley 2720 3370 A qualitative test for urease activity can be Wheat 3275 2670 carried out using a simple colorimetric assay. Soybean meal 2340 3225 Urea-phenol-red solution is brought to an amber Bakery meal 2990 2320 color by using either 0.1 N HCl or 0.1 N NaOH. Tallow 8690 3005 About 25 g of soybean meal is then added to 50 Poultry fat 9020 8680 ml of indicator in a petri dish. After 5 minutes, Corn oil 9660 8840 the sample is viewed for the presence of red Palm oil 7300 9530 particles. If there are no red particles showing, 7700 the mixture should stand another 30 minutes, and again if no red color is seen, it suggests overheating Adapted from Valdes and Leeson (1992, 1994) of the meal. If up to 25% of the surface is covered in red particles, it is an indication of accept- There is also potential for NIRA to predict able urease activity, while 25 – 50% coverage amino acids in ingredients (Table 2.18) as well suggest need for more detailed analysis. Over as antinutrients such as glucosinolates or trypsin 50% incidence of red colored particles sug- inhibitors. As with NIRA analyses, the accuracy gests an under-heated meal. Table 2.18 Prediction of amino g. Protein solubility acids in fish meal Plant proteins are normally soluble in weak Methionine %Amino Acid alkali solution. However, if these proteins are Cystine Assay NIRA prediction heat-treated, as normally occurs during pro- Lysine cessing of many ingredients, the solubility of Tryptophan 1.5 1.6 ± 0.06 protein will decline. Dale and co-workers at Threonine 0.6 0.6 ± 0.07 Georgia have developed a fairly rapid test which Arginine 3.7 4.0 ± 0.30 seems to give a reasonable estimate of protein 0.6 0.5 ± 0.03 solubility and hence protein quality in soybean 2.2 2.3 ± 0.09 meal. The assay involves adding just 1.5 g of soy- 3.4 3.4 ± 0.09 bean meal to 75 ml of 0.2% potassium hydrox- Valdes and Leeson (unpublished) SECTION 2.2 Ingredient testing

CHAPTER 2 83 INGREDIENT EVALUATION AND DIET FORMULATION ide solution, and stirring for 20 minutes. Soluble 2,4 dinitrobenzene (FDNB), which gives a proteins will be in the liquid phase and so all or yellow/orange color when combined with lysine. a portion of the centrifuged liquid is assayed for crude protein, and protein content relative to the Table 2.19 Protein solubility of original 1.5 g sample calculated accordingly. By samples of soybean meal heated for knowing the crude protein content of the orig- various times inal sample of soybean meal, percentage solu- bility can easily be calculated. Typical results, Heating Urease Protein Wt as shown by Dale and Araba are given in Table time (ph solubility gain Feed:Gain 2.19. As heating time is increased, there is a 0 (Raw) change) (%) (g) decrease in protein solubility. Values of 75–80% 5 min solubility seem to be ideal, with higher values sug- 10 min 2.40 99.2 343d 2.44c gesting under-heating, and lower values over-heat- 15 min ing of the protein. A variation of this test is to assess 20 min 2.04 87.7 429c 2.29bc protein solubility in water. Sometimes termed Protein Solubility Index, the results of water sol- 0.23 79.1 481ab 2.00a ubility are said to be more highly correlated with feeding value than are estimates of urease index 0 74.9 496a 2.09ab or protein solubility in KOH. 0 71.8 500a 2.03a Dale and Araba (1987) h. Protein and amino acid i. Fish meal gizzard erosion factor dye-binding In some countries, fish meal is an econom- Proteins will bind with a number of dyes and ical feed ingredient to use in poultry diets. As so this provides the basis for colorimetric assays. previously described, some samples of fish meal These dye-binding techniques can be used to will cause severe gizzard erosion in young birds. test protein per se or used to test for protein in Where fish meal is an integral part of a broiler diet, various extractions involved in assays of solubility then it is common to carry out a chick growth or digestibility. Dye-binding can therefore test with each shipment of fish meal. About 50 replace the Kjeldahl analysis depending upon chicks are fed a broiler starter diet, usually sensitivity needs. The most commonly used without any fish meal, for 5 – 7 days. At this time, methods are as follows: the diet is mixed with 40 – 50% of the test fish meal, and this diet fed for another 7 – 10 days. Cresol Red J. Amer. Assoc. Anal. Birds are then sacrificed and the gizzard exam- Chem. 43:440 ined for erosion, often using a subjective scale Orange G J. Nutr. 79:239 as follows: Coomassie Blue Anal. Biochem. 72:248 1. very mild erosion, with good gizzard Lysine also reacts with certain dyes to give color a colorimetric assay. Carpenter suggested that if the e-amino group of lysine is free to react 2. mild erosion, with evidence of with dye, then the lysine can be considered as destruction of the lining in some areas ‘available’. The most commonly used dye is Fluoro- 3. erosion in localized areas, with cracks in the thinner lining 4. severe erosion, cracking, thinning and discoloration 5. sloughing of the gizzard lining with hemorrhage SECTION 2.2 Ingredient testing

84 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION Because 40 –50% fish meal is used, some seed oil is often suspected. Placing egg yolks in gizzard erosion is expected with most samples. a petri dish with ammonia quickly causes vary- Scores of 4 – 5 are often used to reject samples, ing degrees of brown discoloration depending although this decision will to some extent upon gossypol content. depend upon the level of fish meal to be used in the commercial diet. l. Fat assays j. Sorghum tannins Fat quality is best assessed by measurement of moisture, impurities and individual fatty Tannins are detrimental to protein utilization, acids. However, there are a number of less and so levels should be minimized in poultry diets. extensive tests that can be used to give some idea Sorghum is a potential source of tannin, and this of fat composition and quality. Fat titre is a is usually found in the outer seed coat. measure of hardness, and simply relates to Unfortunately, there is not a clear relationship melting point. The break-point between tal- between seed coat color and tannin content. High lows and greases is about 40˚C. The higher the tannin sorghums are usually darker in color, melting point, the more saturated the fat. Titre but some dark colored sorghums are also low in should obviously be consistent for an individual tannin. The tannins are present in the testa, which class of fat or fat blend from any one supplier. is the layer immediately beneath the outer peri- Iodine value can also be used as a measure of carp. One quick test is therefore to cut into the hardness. Each double bond (unsaturated) will seed and observe for presence of a pigmented take up a molecule of iodine, and so higher val- (tannin) testa. More recently, a bleach test has ues mean a greater degree of unsaturation, been developed which again shows presence, which in turn should relate to lower titre (Table or not, of a pigmented testa. About 20 g of 2.20). Iodine value is greatly influenced by sorghum is mixed with 5 g potassium hydroxide levels of palmitic, oleic and linoleic acid in crystals and 75 ml of household bleach. The most fats and oils. Generally, as titre increases mixture is shaken until the KOH dissolves, and by 10 units over the range of 50 – 100, then then set aside for 20 minutes. Sorghum grains palmitic acid content decreases by about 2%. Also are then strained, rinsed with water and placed as a rule of thumb iodine value = 0.9 x % oleic on a paper towel. The KOH will remove the outer acid + 1.8% x linoleic acid. pericarp, and expose the testa. High tannin grains will appear dark brown/black while low tannin Table 2.20 Iodine value and titre of sorghum will be bleached white/yellow. common fats k. Gossypol in eggs Tallow Iodine Value TitreºC Lard 45 45 Feeding gossypol to laying hens can result in Poultry fat 65 40 discoloration of both the yolk (green-brown) Vegetable oil 80 35 and albumen (pink). Gossypol is usually found 120 15 in cottonseed meal and, as described previ- ously for this ingredient, there are ways to minimize the effects of this compound by diet modification. However, egg discoloration occurs periodically, and cottonseed meal or cotton- SECTION 2.2 Ingredient testing

CHAPTER 2 85 INGREDIENT EVALUATION AND DIET FORMULATION A major concern with the quality of fats and n. Mineral solubility oils, is rancidity or the potential for rancidity. Rancidity is an irreversible oxidative process, that Neutralizing mineral salts with various acids is autocatalylic, meaning that breakdown products can be used to give some idea of mineral avail- fuel further degradation. Rancid fats will be less ability, and when an assay is monitored over time palatable, less digestible, and in extreme cases, the then information on rate of solubility is also process of oxidative rancidity can continue in obtained. Hopefully, all mineral sources will be the body of the bird following consumption of these totally available to the bird, although, at least with fats. The Initial Peroxide Value (IPV) is often used calcium sources, there is concern about solubility. to measure degree of rancidity upon delivery of a Slow solubilization is preferable to very rapid fat. An IPV in excess of 18 – 20 meq is cause for solubilization, because the former more closely concern. If a fat is not stabilized with an antiox- matches the prolonged duration of need for idant, there is potential for subsequent rancidity calcium supply to the shell gland in laying hens. during storage. This potential can be measured by creating extreme conditions for rancidity, name- Limestone solubility can easily be meas- ly bubbling pure oxygen through the heated ured by monitoring pH of the mineral in dilute sample for 24 hr, and re-measuring peroxide acid. After recording the original pH of a 90 ml value. As a word of caution, peroxide build-up is aliquot of 0.1 N HCl, 10 g of limestone is grad- time dependent, since after reaching a peak, there ually added, and without stirring, pH measured is a breakdown of peroxides to other indigestible after time intervals of say 10, 20, 30 and 60 compounds. Therefore fats that have finished minutes. Limestone will result in an increase in oxidizing can show a low peroxide value, but have pH, as H+ ions are liberated from solution. A very poor nutritive value. Such samples are best pH change of +0.1 relates to a 20% solubility, detected by their ‘rancid smell’. while changes of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 and 1.0 relate to about 37, 50, 60, 70, 75, m. Hulls in rice by-products 80, 84, 87 and 90% solubility respectively. A pH change of +2.0 means 99% solubility. A high Rice bran, sometimes called rice pollard, is solubility after 60 minutes is expected from a used extensively in rice growing areas of the world. quality limestone, whereas the rate of achieving The major variable affecting nutritive value, is the 95 – 99% solubility will give an indication of the content of hulls, which are essentially indi- rate of calcium release in the proventriculus. gestible for poultry. A major component of hulls Particle size and particle porosity are the factors is lignin, and this reacts with the reagent phloroglu- most likely to affect rate of change of solubility. cinol to produce a color reaction. The reagent Optimum eggshell quality, and perhaps bone devel- is produced by combining 1 g of phloroglucinol opment in young birds, are dependent upon a with 80 ml 2M HCl and 20 ml ethanol. The rice consistent pattern of calcium solubility. by-product is mixed 1:2 with reagent and held at about 25ºC for 10 minutes. Development of Neutralization of ammonium citrate has red color will be directly proportional to hull been used to assess solubility of phosphate content. Actual hull content and a color score- sources and also of manganese and zinc salts. card are necessary to ‘calibrate’ the assay. SECTION 2.2 Ingredient testing

86 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION A2.3 FEED ADDITIVES sion levels of around 5 – 12 kg/tonne. There have number of additives are often used in poul- been reports of colloidal-clay type products try diets and most of these do not con- binding some B-vitamins and pigments in the gut, tribute any nutrients per se. Most and so making them unavailable to the bird. The additives are used to improve physical diet colloidal-clay products may also aid in reduc- characteristics, feed acceptability or bird health. ing apparent moisture content of the bird’s exc- The following discussion is not intended to reta and more recently, some forms of clay have emphasize efficacy of the various products but been shown to have activity in binding aflatoxin. rather to highlight various implications of their The lignosulfonate pellet binders often contain use in terms of diet formulation, ingredient 20 – 30% sugars, and so contribute to diet compatibility and/or general feeding management. energy level. Studies show lignosulfonate binders to have ME values of 900 – 2200 kcal/kg a. Pellet binders depending upon sugar content. Because these binders are often used at 1 – 1.2% of the diet, When pellet quality is of concern, a pellet then energy contribution is meaningful at 10 –25 durability index is often ascribed to ingredients kcal/kg of diet. and this is considered during formulation. This index may range from 55 – 60 for corn soy diets b. Anticoccidials that are notoriously difficult to pellet, to 90 – 95 for wheat-based diets. With corn-based diets, it Anticoccidials are used in diets for most is often necessary to use synthetic pellet binders meat birds and young breeding stock that are reared in order to achieve desirable pellet quality. In most on litter floors. Over the past 20 years, the so- instances, the need for a good pellet is necessary called ionophore anticoccidials have predom- to placate the purchaser of the feed, because the inated and they have proved most efficacious in bird per se is often tolerant of a range of quality controlling clinical signs of coccidiosis. From in terms of growth rate and feed efficiency. The a nutritional viewpoint, some care must be turkey poult is perhaps the most sensitive to taken in selection of these products as they can pellet or crumble quality, where growth rate influence metabolism of the bird under certain can be markedly influenced by both pellet size situations. and the proportion of fines. The pelleting process is discussed in more detail in the following Monensin has been a very successful section on Feed Mixing and Pelleting. anticoccidial, and seems to work well with both broiler chickens and turkeys. Monensin, A number of pellet binders are available, like most ionophores, has an affinity to bind metal although they are used at considerably different ions, the most important in terms of bird metab- inclusion levels, and such levels should be olism being sodium and potassium. Lasalocid clearly specified for each product. When wheat also binds metals, although its major affinity is or wheat by-products are used at less than 10% for potassium and secondly, sodium. Most of the diet, then a binder will often be necessary ionophores also increase the permeability of if high pellet durability is desired. The two membranes to H+ ions, a factor that may be major types of binders have lignosulfonate or of significance in acid-base balance. For this colloidal clays as the base product, with inclu- SECTION 2.3 Feed additives

CHAPTER 2 87 INGREDIENT EVALUATION AND DIET FORMULATION reason, there needs to be more work conducted levels is often ignored, and as a consequence on ionophores for heat-stressed birds. Ionophores performance is sub-optimal. The relationship have been shown to alter mineral availability, between ionophores and water intake has not been although this should not be of concern under fully resolved other than the fact that birds fed commercial conditions where most minerals monensin do seem to produce drier manure. are present in excess of requirements. Studies show that the effect of ionophores on mineral Non-ionophore anticoccidials are not used metabolism is not always consistent for various extensively in chicken broiler production, minerals. For example, monensin may lead to although their use is often recommended in increased tissue level of certain minerals, while shuttle programs. Nicarbazin is an anticoccidial lasalocid has the opposite effect, yet for another that seems to work well in such shuttle programs, mineral these effects could be reversed. although again there are some potential problems with this product. Nicarbazin seems Ionophores, and monensin in particular, to accentuate the undesirable effects of heat seem to have an adverse effect when used in con- stress, and if inadvertently added to layer or junction with low protein (methionine) diets. When breeder diets at normal anticoccidial levels, low protein diets or feed restriction are employed can cause loss in reproductive performance. for birds less than 21 d of age, alternatives to Nicarbazin fed to brown egg birds turns their ionophores should be considered in an attempt eggshells white within 48 hr although this is to alleviate potential growth depression, loss of completely reversible when the product is with- uniformity and poor feathering. However, with drawn from the feed. Even low levels of normal diet protein levels, the ionophores do not nicarbazin can cause some loss in shell color, have a measurable effect on TSAA requirement. and mottling of egg yolks, and loss in fertility and Ionophores and monensin in particular do hatchability of breeders. impart some growth depression in young birds, although this seems to be completely overcome Amprolium is used extensively in diets for with compensatory growth during the with- growing breeder pullets, because unlike the drawal or finisher period. For monensin, a 5 – 7 d ionophores, it allows some build-up of withdrawal is optimum for compensatory gain, immunity. Amprolium induces a thiamin deficiency assuming that no major coccidiosis challenge will in the developing oocysts, and as such, has occur during this time. With minimal challenge, been queried with respect to thiamin status of the a non-medicated withdrawal diet is recom- bird. In most instances thiamin deficiency will mended, while in situations of high challenge, not occur in birds, although cases have been an alternative anticoccidial may be necessary. reported of combinations of amprolium and poorly processed fish meal that is high in There has also been some controversy on the thiaminase enzyme, leading to thiamin relationship between wet litter and certain deficiency in young birds. ionophore products. Lasalocid in particular has been associated with wet litter, and as such, Coccidial vaccines are now commonly used recommendations are often given for reducing in breeders, and their use will likely increase for diet sodium levels when this anticoccidial is used. broilers. There has been some discussion about Under such conditions adjustment of chloride diet manipulation so as to improve the immune SECTION 2.3 Feed additives

88 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION response. Oocysts start to cycle when birds are Without the use of such ‘antibiotics’, there will 10 d of age, and if the litter is exceptionally dry undoubtedly be greater risk of bacterial overgrowth this important cycling is less effective. Under such in the bird’s digestive tract and especially when extreme conditions, it may be advisable to ‘poorly’ digested ingredients are used since temporarily increase diet or water sodium these provide substrates for microbial fermentation levels, so as to stimulate water intake. in the lower gut. Such enhanced microbial growth can have various consequences for the c. Antibiotics, Growth bird. If the microbes are pathogens, then disease Promoters can occur. With proliferation of non-pathogens there can still be effective loss of nutrients to There has been a gradual reduction in the use the bird and undoubtedly such conditions of antibiotics per se, although growth promot- contribute to ‘feed passage’ where feed particles ing agents are still used extensively in most can be seen in the excreta. Using germ-free regions. The mode of action of growth promoting (gnotobiotic) birds, there is invariably a decrease agents is comparable to that of antibiotics in terms in diet AMEn, since there is no ‘digestion’ by of beneficial modification of gut microflora. In microbes. this context, the type of dietary ingredients used may influence the efficacy of these products There will undoubtedly be future interest in because microbial activity is influenced by developing nutritional strategies aimed at digesta composition. There has been insuffi- reducing our reliance on sub-therapeutic cient work conducted in this area, e.g. the antimicrobials. In general, such strategies revolve beneficial effect seen when antibiotics are used around limiting the nutrient supply to the intestinal with ingredients such as rye. It is unlikely that microbes, altering the lumen environment so as growth promoters result in increased digestibil- to hinder microbial growth and/or priming or ity of feed, rather improvements in feed efficiency improving the bird’s immune response (Table 2.21). are a consequence of increased growth rate and hence reduced days to market. Over the past If diets are made more digestible, then few years, there has been criticism about the use theoretically, there should be fewer substrates of antibiotics in poultry feeds, especially with available for microbial growth. The greatest respect to the potential for build-up of microor- success in this area will likely occur from ganisms resistant to a specific antibiotic, and developments in feed processing and greater subsequent transfer of this resistance to known application of exogenous feed enzymes. There pathogens. In this context, the use of antibiotics seems great potential for modifying gut pH, such as penicillin, that are also used in human- either with use of feed or water source acids, or medicine, come under very close scrutiny. simply by stimulating gizzard activity. Many organic acids are bactericidal, and while some It is very difficult to grow broilers without the are corrosive, there are few limitations in adding use of growth promoters, since clostridial organ- them to diets in terms of stability of most other isms often proliferate and clinical necrotic nutrients. While such acids may not have a dra- enteritis develops. While some countries have matic effect on pH of the small intestine, a ban on sub-therapeutic growth promoters in products such as lactic acid are bactericidal the feed, their use is escalating as water additives. over quite a range of pH. SECTION 2.3 Feed additives

CHAPTER 2 89 INGREDIENT EVALUATION AND DIET FORMULATION Table 2.21 Nutritional strategies to reduce reliance on sub-therapeutic growth promoters 1. Limit microbial growth by Areas of study Examples limiting their nutrient 1. Use more digestible Corn vs small grains supply ingredients Pelleting, expansion etc. 2. Limit microbial growth by 2. Feed processing NSP, lipase? manipulating digesta pH 3. Use of feed enzymes Increased use synthetic AA’s 4. Reduce diet nitrogen 3. Improve immunity to Phosphoric, propionic, lactic acids infection 1. Feed/water acids Feed whole grain or large feed 2. Stimulate gizzard particles. 4. Interfering with sites of bacterial attachment activity Coccidiosis Fatty acids, Vitamin E 1. Vaccines 2. Prime the immune Mannanoligosaccharides system 1. sugars Laying hens and especially broiler chickens charides (MOS). Gram-negative bacteria have today have very rudimentary gizzards. With mannose specific fimbriae that are used for increased gizzard activity, there will be greater HCl attachment to the gut wall. Mannan derivates production from the proventriculus and this is obvi- from the cell wall of yeast offer the bacterial ously bactericidal. Stimulating gizzard growth and fimbriae an alternate binding site, and consequently activity may, therefore become more important, are excreted along with the undigested mann - and contribute to health management of the anoligosaccarhride. Adding 1 – 3 kg of MOS per birds There are often reports of higher digestibil- tonne feed, depending on bird age, will likely be ity of broiler feeds when particle size of feed is part of future strategies for growing birds on reduced. However, in most of these trials, the ‘antibiotic-free’ diets. ‘young’ broilers likely have a rudimentary gizzard. For birds that have previously been fed larger size The other issue involving use of antibiotics particles and/or more fiber, such that gizzard and growth promoters in poultry feeds is the activity is increased, then there is greater digestibil- potential for tissue or egg accumulation of these ity of feed with a larger particle size. Gizzard func- compounds. Adherence to regulated withdrawal tion is generally a factor of fiber content of the feed, periods eliminates these problems, as does together with consideration of feed particle size. scheduling of mixing non-medicated and med- icated feeds in the mill. Most countries are As detailed in Table 2.21 another potential now establishing GMP and HACCP programs at substitute for antibiotics is mannanoligosac- SECTION 2.3 Feed additives

90 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION feed mills to eliminate any potential for Unfortunately, relatively high levels of alumi- antibiotic residues in poultry products. nosilicates must be used and these provide no other nutrients and may, in fact, act as chelating A number of ingredients are still referred to agents for some essential minerals. However, as having ‘unidentified growth factors’. On where aflatoxin contamination is common, then this basis, ingredients such as alfalfa meal, adding up to 15 kg aluminosilicates per tonne distiller’s solubles, bakery yeasts and animal of feed may be necessary in order to minimize proteins are often added at 1 – 2% of the diet. the effect of this mycotoxin. Any ‘unexplained’ response to these ingredients most often relates to their containing trace In addition to, or as an alternative to using such levels of vitamin or natural antibiotic residues. antifungal agents, there is a potential for minimizing mold growth through formulation, d. Antifungal agents diet preparation and feeding management. There seems little doubt that the feed surface area is direct- In many regions of the world, molds and ly related to potential fungal activity since the greater associated mycotoxins are major problems, the surface area of feed exposed to the atmosphere, affecting both growth and reproductive the greater the possibility of fungal spore colonization. performance. Mycotoxins produced by both This fact is the most likely cause for the increase aerobic field molds and anaerobic storage molds in mold growth often seen with feed as it travels can accumulate, often undetected, in a range of from the mill to the feed trough because particle ingredients. A number of antifungal agents are size is invariably reduced. Up to a 50% increase available, most of which are based on organic acids. in fines can occur with high-fat pelleted broiler diets By altering the pH of the feed, it is hoped to con- between the time of pelleting and consumption by trol mold growth, although it must be remembered the bird. At the same time, there is a 100% that any mycotoxin already present in feed will increase in the potential (and most often the not be destroyed by these antifungal agents. occurrence) of fungal activity. In areas of poten- Apart from their cost, these organic acids can be tial mycotoxin contamination, there is obviously problematic in accelerating the corrosion of an advantage to maintaining as large a pellet or crum- metal feeders and mill equipment. ble size as possible. The heat generated during pel- leting has been shown to sterilize feed to some extent, Gentian violet is also used in many countries because fresh pellets have low fungal counts. as an antifungal agent, and in this context, its effi- However, pelleting will not destroy mycotoxins already cacy is governed by factors that determine the formed prior to pelleting, and warm moist pellets efficacy of organic acids (i.e.: time, tempera- are an ideal medium for fungal growth. Research ture, moisture and feed particle size). Gentian vio- has shown increased fungal activity in feed taken let also has some bacteriostatic activity and as such, from trough vs tube feeders with the former hav- is often used to maintain a beneficial gut microflo- ing more feed exposed to the atmosphere. ra, comparable to an antibiotic. In recent years, there has been some interest in use of alumi- With toxins such as aflatoxin, there is a nosiliacate (zeolites) as an ‘adsorbent’ of aflatoxin, benefit to increasing the protein content of the and also products based on yeast cell walls. diet, and in particular, sulfur amino acids. It is possible that sulphates may also be beneficial in SECTION 2.3 Feed additives

CHAPTER 2 91 INGREDIENT EVALUATION AND DIET FORMULATION helping to spare sulfur amino acids that are in number of Lactobacilli at the expense of catabolized during aflatoxicosis. Due to the coliforms. A healthy animal has a preponder- specific enzyme system involved with aflatox- ance of lactic acid producing bacteria, and so icosis, selenium at up to 0.4 ppm may be it is only under situations of ‘stress’, when beneficial in overcoming major adverse effects coliforms often increase in numbers, that probiotics of this mycotoxin. There have also been reports will be of measurable benefit. In this context there of niacin increasing the catabolism of aflatoxin is interest in the use of live cultures administered B1, and so decreasing overall toxicity. (orally) to day-old poultry as a means of preventing harmful bacteria such as salmonella from It appears that diet modification and feed colonizing the gut. management can be manipulated to minimize chances of mycotoxicosis. However, such The term ‘competitive exclusion’ is often measures will not likely be 100% effective, and used synonymously with probiotics. It is assumed it should always be remembered that most that the probiotic will have a competitive advan- fungal growth can be reduced if moisture tage over any inherent pathogen, and either content of grains and feeds is kept below 14 – 15%. replace it, or prevent its colonization. Bacterial antagonism may arise due to synthesis of e. Probiotics and Prebiotics inhibitors by the probiotic organism. Lactic acid from Lactobacilli and other species is an Probiotics, unlike antibiotics, imply the use example of such a product. Probiotic organisms of live microorganisms rather than specific may also stimulate mucosal immunity. While products of their metabolism. Not being specific undefined mixtures of bacteria, usually derived molecules therefore, they are difficult to from cecal contents of healthy adult birds, seem quantitate and even more difficult to describe in to be effective probiotics, regulatory agencies are terms of proposed modes of action. Probiotics often concerned about dosing animals with can be classified into two major types – viable unknown organisms. Defined synthetic mixtures microbial cultures and microbial fermentation of bacteria seem less efficacious at this time, products. Most research has centered on possibly because we have only scant knowledge Lactobacilli species, Bacillus subtilis and some of the normal (beneficial) microbial population Streptococcus species. Similar to the situation within a healthy bird. However, this approach with antibiotics, the mode of action is still to developing a probiotic probably has the best unclear although the following have been long-term chance of success. With potential suggested: a) beneficial change in gut flora with instability in most feeds for many Lactobacillus reduction in population of E. Coli; b) lactate species, there has been recent interest in probiotics production with subsequent change in intestinal based on Bacillus subtilis species, because they pH; c) production of antibiotic-like substances; possess a viable spore that has greater stability d) reduction of toxin release (suppression of than do most lactic acid producing cultures. E. coli). With these varied potential routes of activity, it is perhaps not too surprising that Regardless of somewhat inconclusive results, research results are inconsistent. In most it appears that probiotic use is increasing, and instances, the feeding of live cultures modifies that the animal industry looks to such products the gut microflora of birds usually with increases as the substitutes for conventional antibiotics. These SECTION 2.3 Feed additives

92 CHAPTER 2 INGREDIENT EVALUATION AND DIET FORMULATION products seem ideal candidates for genetic ance is not fully understood. Yeasts may beneficially manipulation which has been inferred by a alter the inherent gut microflora, possibly through number of researchers in this area. By using controlling pH. The presence of living yeast genetic engineering, some researchers suggest cells may also act as a reservoir for free oxygen, that bacteria can be reformed to carry more which could enhance growth of other anaerobes. desirable gene characteristics, including the At the present time, there does not seem to be any production of digestive enzymes and antimicrobial move to manipulate yeast for specific purposes substances. related to animal nutrition. To some extent, this relates to scant knowledge on mode of action, and Prebiotics are aimed at supplying probi- so should more facts be uncovered in this area otics with an advantageous source of nutrients, so-called ‘designer’ yeast may be considered. implying that their needs are different to those of the host and/or different to those of potential g. Enzymes pathogens. Certain oligosaccharides, which resist endogenous enzyme degradation, seem to Enzymes have been added to poultry diets ever promote a more favorable microflora in the since workers at Washington State University lower small intestine and also the large intestine. showed improvement in digestibility of barley and However, certain pathogenic bacteria, such as rye-based diets when various enzymes were Clostridium perfringens are also able to ferment used. In the 1950’s, corn-soybean diets pre- some of the oligosaccharides. There is some dominated, and these were assumed to be preliminary work with pigs suggesting synergism highly digestible and so there was little interest for certain combinations of prebiotics and in feed enzyme application. Over the past few probiotics, which is expected if both are efficacious. years, this area of nutrition has gained interest and activity due to economics of small grain use f. Yeasts and also because of a better understanding of mode of action and availability of various enzymes. Yeast, or single-celled fungi, have been used in Enzymes are now being manufactured specifically animal feed and the human food industry for for feed use, and can be broadly categorized as many years. Brewer’s yeast was a common feed carbohydrases, proteinases and lipases. Increasing ingredient in diets for monogastric animals prior to the digestibility of various carbohydrate the identification of all the B-vitamins. Today, fractions of cereals and plant proteins has received some nutritionists still incorporate these most attention, although there is growing inactivated microbes as a source of so-called interest in the potential for improving digesti- ‘unidentified growth factor’. More recently there bility of both plant and animal proteins, and of has been an interest in the use of live yeast saturated fatty acids for young birds. Currently, cultures. These cultures most often contain the yeast enzymes are used most commonly to aid themselves and the medium upon which they digestion of diets containing wheat, barley and have been grown.Yeast cultures are usually derived rye where improvements are seen in dry matter from Saccharomyces species, in particular, digestibility and also in consistency of the Saccharomyces cerevisiae. As with probiotics, their excreta. There is also current interest in enzymes mode of action in enhancing animal perform- designed specifically to improve soybean meal digestibility. SECTION 2.3 Feed additives

CHAPTER 2 93 INGREDIENT EVALUATION AND DIET FORMULATION The term non-starch polysaccharides (NSP) polymers of sucrose. Most cell wall NSP’s is now frequently used to describe what in the either exist alone or as structural material often past has been referred to as fiber. Birds have a complexed with protein and lignin. Solubility of very limited ability to digest fiber because they NSP’s usually relates to the degree of binding to lack the enzymes necessary to cleave these lignin and other insoluble carbohydrates. In water, large and complex molecules. In animals such most NSP’s produce a very viscous solution, and as the pig, and in ruminants, it is the resident micro- this has a predictably negative effect on diges- bial populations that synthesize cellulase type ta flow and interaction of all substrates with enzymes that allow for varying degrees of fiber their endogenous enzyme systems. Some NSP’s digestion. If we can improve digestion of the such as pectins, have a three-dimensional struc- complex carbohydrates, we not only increase ture that can chelate certain metal ions. Any potential energy utilization, but also remove increase in digesta viscosity causes an increase any negative impact that these products may have in thickness of the unstirred water layer adjacent on gut lumen activity and excreta consistency. to the mucosal villi. Consequently, there is reduced solubilization and uptake of most nutri- The NSP content of cereals and other by- ents. Digesta retention time increases, but product feeds is usually inversely proportional because of the increased viscosity there is less to their conventional energy level. These NSP opportunity for substrates to contact enzymes. components are most often associated with the There are also more endogenous secretions and hull and underlying aleurone layers. In order for these contain proportionally more bile acids. In normal endogenous enzymes to contact the addition to reduced digestibility, there are also starch endosperm, these outer layers must be reports of reduced net energy of diets due to NSP’s. disrupted or chemically degraded. Although many The reduced NE may be a consequence of compounds fit into the category of NSP’s, there increased energy expended by the digestive are three main types of importance in poultry system in simply moving digesta through the sys- nutrition. These are the ß-glucans in barley, the tem. The increased digesta viscosity also influ- arabinoxylans or pentosans in wheat and the raf- ences the gut microflora and there is an indication finose group of oligosaccharides in soybeans. Barley that their overgrowth may, in fact, add to the over- ß-glucans are polymers of glucose while arabi- all deleterious effects. To the poultry producer, noxylans contain long chains, and cross chains the most notable effect of NSP’s will be wetter, of fructose. The oligosaccharides in soybean are more sticky and viscous excreta. Table 2.22 details Table 2.22 Non-starch polysaccharides in selected ingredients (%) Ingredient Cellulose Arabinoxylan Pectin ß-glucans Corn 2.5 5.0 0.1 - Wheat 2.5 6.0 Barley 4.8 7.0 0.1 1.0 5.01 0.5 Soybean meal 0.2 4.0 – 5.0 12.0 - 1 depending on hull fraction returned SECTION 2.3 Feed additives