Commercial_Poultry_Nutrition

144 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS However, grower is fed for two weeks longer than to light stimulate this flock a week earlier than normal, during weeks 13 and 14, to ensure ideal scheduled, with appropriate early introduction weight at 17 weeks. of the layer diet. Table 3.28 shows examples for feed sched- The examples shown in Table 3.27 and Table uling of brown egg birds where increased growth 3.28 emphasize the need for flexibility in feed is the problem. In Scenarios 1 and 2, the pul- scheduling. For most flocks, the end goal will lets are overweight at various ages according to likely be the breeder’s recommended target the standard. In Scenario #1, pullets are over- weight at 16-18 weeks or whenever light stim- weight at 5 weeks and so the lower nutrient dense ulation occurs. In certain situations it may be nec- grower diet is introduced a week early. Likewise essary to manipulate mature body weight accord- developer diet type is used from 10 rather than ing to economics of manipulating egg size and 11 weeks. In Scenario #2, pullet growth is egg grade (see Section d). As a generalization, much higher than standard. This growth is tem- the smaller the body weight of the pullet, the small- pered somewhat by earlier introduction of grow- er the size of the egg throughout the entire lay- er and developer diets, yet pullets are still over- ing cycle. Conversely, a larger pullet will always weight at 16 weeks. Because such rapid growth produce a bigger egg and this is little influ- will result in earlier maturity it may be advisable enced by layer nutrition. Table 3.27 Feeding scenarios for White pullets according to growth (g) Standard Scenario #1 Scenario #2 Week(s) Body Feed type Body Feed type Body Feed type wt. wt. wt. 1 70 Starter 70 Starter 70 Starter 2 135 Starter 130 Starter 135 Starter 3 205 Starter 190 Starter 205 Starter 4 280 Starter 255 Starter 280 Starter 5 365 Starter 320 Starter 365 Starter 6 450 Starter 400 Starter 450 Starter 7 535 Grower 500 Starter* 535 Grower 8 620 Grower 600 Starter* 620 Grower 9 700 Grower 700 Starter* 650 Starter* 10 775 Grower 775 Grower 720 Starter* 11 845 Grower 845 Grower 800 Starter* 12 915 Grower 915 Grower 870 Grower 13 975 Developer 975 Developer 950 Grower* 14 1035 Developer 1035 Developer 1000 Grower* 15 1095 Developer 1095 Developer 1095 Developer 16 1165 Developer 1165 Developer 1165 Developer 17 1235 Developer 1235 Developer 1235 Developer * different from standard SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 145 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Table 3.28 Feeding scenarios for ISA Brown pullets according to growth (g) Week(s) Standard Scenario #1 Scenario #2 Body Feed type Body Feed type Body Feed type wt. wt. wt. 1 50 Starter 50 Starter 50 Starter 2 100 Starter 110 Starter 110 Starter 3 190 Starter 200 Starter 210 Starter 4 280 Starter 290 Starter 320 Grower* 5 380 Starter 420 Grower* 460 Grower* 6 480 Grower 510 Grower 550 Grower 7 580 Grower 600 Grower 650 Grower 8 675 Grower 700 Grower 780 Developer* 9 770 Grower 790 Grower 900 Developer* 10 850 Grower 870 Developer* 980 Developer* 11 950 Developer 960 Developer 1050 Developer 12 1040 Developer 1040 Developer 1200 Developer 13 1130 Developer 1130 Developer 1260 Developer 14 1220 Developer 1220 Developer 1320 Developer 15 1300 Developer 1300 Developer 1350 Developer 16 1390 Developer 1390 Developer 1430 Layer* * different from standard Table 3.29 Effect of immature body weight on development to sexual maturity Body weight (g) Age at first Weight of egg (d) first egg (g) 18 wks 1st egg Change 153 40.7 1100 1360 +260 150 42.0 149 43.7 1200 1440 +240 148 42.5 1280 1500 +220 1380 1590 +210 An argument that is often heard about the role For the smaller pullet there is a degree of com- of body weight at maturity, is that it is not in fact, pensatory growth up to the time of the first egg, too important because the pullet will show although this is insufficient to allow for total ‘catch- catch-up growth prior to first egg. In other up’ growth. It is also interesting to note the rela- words, if the pullet is small, it will take a few days tionship between body weight and age at first egg longer to mature, and start production at the ‘same and also between body weight and size of first weight’. However, this does not seem to hap- egg. In other studies, we have monitored the pen, as small birds at 18 weeks are smaller at time growth of pullets through a production cycle in of laying their first egg (Table 3.29). relation to 18 week body weight which is the age of light stimulation. Again, there is a remarkably SECTION 3.3 Feeding management of growing pullets

146 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Fig. 3.3 Effect of immature body weight on subsequent body weight during lay. similar pattern of growth for all weight groups brown egg strains will likely mature 7-10 d ear- indicating that immature weight seems to ‘set’ lier than the Leghorn strains. the weight of the bird throughout lay (Figure 3.3). d) Manipulation of body weight More importantly from a production viewpoint, at sexual maturity is the performance of birds shown in Figure 3.3. When the lightest weight birds were fed diets of In the previous section, the main emphasis very high nutrient density (20% CP, 3000 kcal was on attaining the breeder’s recommended ME/kg) they failed to match egg production and weight at time of sexual maturity. Under certain egg size of the largest weight pullets that were fed conditions, some tempering of mature body very low nutrient dense diets (14% CP, 2600 kcal size may be economically advantageous. Because ME/kg). These results emphasize the impor- body size has a dramatic effect on egg size, large tance of mature body weight in attaining maxi- birds at maturity can be expected to produce large mum egg mass output. eggs throughout their laying cycle. Depending upon the pricing of various egg grades, a very large The actual body weight achieved will obvi- egg may be uneconomical to produce, and in most ously vary with strain and bird type (Tables instances tempering of egg size of birds from 40- 3.12, 3.19). For Leghorns, weight should be around 65 weeks of age is often difficult to do without 400-450 g at 6 weeks, 850-1000 g at 12 weeks associated loss in egg numbers. Because body and 1200-1300 g at 18 weeks. The brown egg weight controls feed intake and egg size, an eas- strains will be 450-480 g at 6 weeks, 1000 g at ier way of manipulating life-cycle egg size is 12 weeks and 1500-1600 g at 18 weeks. The through the manipulation of mature body size. SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 147 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS If the maximum possible egg size is desired, then which in this scenario means moving at 17 rather efforts must be made to realize the largest pos- than 18 weeks of age. Moving the bird, and sible mature weight. However, where a small- light stimulating at 17 vs. 18 weeks will have no er overall egg size is economical then a small- adverse effect on performance, as light stimulation er pullet is desirable. Such lightweight pullets is still at the desired body weight standard (that has can be obtained by growing pullets more slow- been achieved one week earlier than anticipated). ly or most easily by light-stimulating pullets at an earlier age. Figure 3.4 gives a schematic rep- Early maturity is not a problem for flocks that resentation of the above concept. In this scenario, have ideal body weight and condition. Early matu- birds are on the heavy side of the breeder’s rity and light stimulation will only result in sub- weight guide, and so if moved at 18 weeks, would sequent small egg size and increased incidence be heavier than the ideal weight and be expect- of prolapse if the bird is small at this age. This ed to produce very large eggs. If this situation concept is preferred over attempts at trying to slow is not economical in the laying house, then the bird down during growth in an attempt to delay these birds should be moved at the ‘ideal weight’ maturity (Figure 3.5). Fig. 3.4 Light stimulation at target weight rather than age. SECTION 3.3 Feeding management of growing pullets

148 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Fig. 3.5 Potentially harmful adjustment to pullet weight. Such adjustments are invariably brought about tion on nutrient flow for pullets through to 18 by use of very low nutrient dense diets and/or use weeks. On a per pullet basis therefore, each bird of restricted feeding. Both of these practices have produces about 0.1 kg N and 0.03 kg P in the the desired ‘effect’ of slowing down mean growth, manure to 18 weeks of age. but at the great cost of loss of pullet uniformity. Manure nutrient loading is in direct pro- e) Nutrient management portion to corresponding diet nutrient levels. Using lower protein or lower phosphorus diets will invari- Although growing pullets do not produce large ably result in less of these elements appearing quantities of manure in relation to adult layers, in the manure. Attempts at reducing crude nutrient loading of manure will likely be a man- protein levels in pullet diets, as a means of agement consideration. Under average condi- reducing feed cost and/or manure N loading, often tions of feeding and management, pullets will retain results in poor growth rate (Table 3.31). Regardless about 25% of nitrogen and 20% of phosphorus of constant levels of the most important amino consumed. Most of the remaining phosphorus acids in these diets, pullets responded adverse- will be retained in the manure while around 30% ly to any reduction in crude protein. This data of the excreted nitrogen will be lost as ammo- suggests that pullets have minimal needs for nia, either in the pullet house or during storage non-essential amino acids and/or that require- prior to land disposal. Based on these values for ments for amino acids such as threonine and nutrient balance, Table 3.30 provides informa- arginine are of more importance than normally SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 149 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Table 3.30 Nitrogen and phosphorus balance for 50,000 pullets to 18 weeks of age Intake (kg)1 Body retention Excretion Gas Loss Manure (kg) (kg) (kg) (kg) 1760 5000 Nitrogen 7680 1920 5760 - 1560 Phosphorus 1950 390 1560 1Assumes 6 kg feed per pullet, averaging 16% CP (2.56% N) and 0.65% total phosphorus Table 3.31 Body weight of Leghorn and brown egg pullets fed low protein diets with constant levels of TSAA, lysine and tryptophan Diet CP (%) Brown bird weight (g) Leghorn weight (g) Starter1 Grower2 56d 98d 126d 56d 98d 126d 20 16 746a 1327a 1524a 592a 1086a 1291a 18 14 16 12 720b 1272b 1471b 576b 1046b 1235b 14 10 706b 1144c 1301c 546c 921c 1085c 540c 989d 1175d 434d 781d 932d 1 0.66% TSAA: 0.90% lysine; 0.24% tryptophan 2 0.55% TSAA; 0.72% lysine; 0.19% tryptophan Table 3.32 Effect of dietary phosphorus on pullet development and phophorus excretion Diet available P (%) Body weight (g) Feed intake Tibia Manure P Starter Grower Developer 6 wk 18 wk (kg) ash (kg/1000) (%) 0.40 0.35 0.30 345 1210 5.94 28 0.30 0.25 0.20 340 1260 5.98 50.7 24 0.20 0.15 0.10 330 1200 5.85 49.3 18 48.8 Adapted form Keshavarz (2000) estimated. Regardless of mode of action, it well with the prediction shown in Table 3.30. It seems that there is only limited potential to seems as though there is potential for at least 30% reduce the crude protein levels in pullet diets as reduction in manure P output of pullets through a means of reducing manure nitrogen loading. diet formulation. There does seem to be potential for reducing diet phosphorus levels in pullet diets, to limit manure f) Prelay nutrition and loading. Keshavarz (2000) shows acceptable pul- management let growth with diet levels as low as 0.2% in the starter diet (Table 3.32). There was an indication i) Considerations for calcium metabolism – of slightly lower egg production to 30 weeks of Prelay diets and prelay management are designed age in pullets fed the lowest level of diet P, to allow the bird the opportunity to establish ade- although growth characteristics were little affect- quate medullary bone reserves that are neces- ed. The P loading of manure of 28 kg/1000 agrees SECTION 3.3 Feeding management of growing pullets

150 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS sary for calcifying the first egg produced. In prac- comb and wattles. Consequently, there will tice, there is considerable variation in formula- be little medullary deposition, regardless of diet tion and time of using prelay diets, and to some calcium level, if the birds are not showing comb extent this confusion relates to defining sexual and wattle development and this stage of matu- maturity per se. Historically, prelay diets were rity should be the cue for increasing the bird’s fed from about 2 weeks prior to expected matu- calcium intake. rity, up to the time of 5% egg production. With early, rapid and hopefully synchronized matu- Because egg production is an ‘all or none’ ration with today’s strains, we rarely have the oppor- event, the production of the first egg obviously tunity to feed for 2 weeks prior to maturity. places a major strain on the bird’s metabolism Likewise, it is unwise to feed inadequate levels when it has to contend with a sudden 2 g loss of calcium when flocks are at 5% production. of calcium from the body. Some of this calcium One of the major management decisions today will come from the medullary bone, and so is the actual need for prelay diets, or whether pul- the need to establish this bone reserve prior to lets can sustain long-term shell quality when moved first egg. The heaviest pullets in a flock will like- from grower diet directly to a high calcium ly be the first to mature, and so it is these birds layer diet. that are most disadvantaged if calcium metab- olism is inadequate. If these early maturing The bird’s skeleton contains around 1 g of pullets receive a 1% calcium grower diet at medullary calcium that is available for shell cal- the time they are producing their first few eggs, cification on any one day. This calcium is con- they will only have a sufficient calcium reserve tinually replenished between successive ovula- to produce 2-3 eggs. At this time, they will like- tions, and in times of inadequate calcium repletion, ly stop laying, or less frequently continue to the medullary reserve may be maintained at the lay and exhibit cage layer fatigue. If these ear- expense of structural cortical bone. Around 60- lier maturing birds stop laying, they do so for 4- 70% of the medullary calcium reserves are locat- 5 days, and then try to start the process again. ed in the long bones, and so long-term problems The bird goes through very short clutches, when of calcium deficiency can lead to lameness and at this time she is capable of a very prolonged cage layer fatigue. 30 – 40 egg first clutch. Advocates of pro- longed feeding of grower diets suggest that it makes Prelay diets normally contain 2-2.5% calcium, the bird more efficient in the utilization or and when fed over a 10-14 d period provide the absorption of calcium, such that when she is even- bird with the opportunity to deposit medullary tually changed to a layer diet, improved efficiency bone. This bone deposition coincides with fol- continues for some time, with the bird having more licular maturation and is under the control of both calcium available for shell synthesis. Figure estrogens and androgens. The latter hormone 3.6 indicates that percentage calcium absorption seems essential for medullary bone growth, from the diet does decline with an increased level and its presence is manifested in growth of the of calcium in the diet. SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 151 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Fig. 3.6 Relationship between calcium intake and calcium retention. However, with 40% retention of 5 g of cal- build up of medullary reserves without adverse- cium consumed daily, there will be greater ly influencing general mineral metabolism. absolute calcium retention (2 g/d) than the bird However, as previously discussed for grower diets, consuming 2.5 g Ca/d and exhibiting 60% effi- 2 – 2.5% calcium prelay diets are inadequate for ciency of retention (1.5 g retained/d). There is sustained egg production, and should not be fed also no evidence to support the suggestion of carry beyond 1% egg production. The main disad- over of this higher efficiency during early egg pro- vantage of prelay diets is that they are used for duction. If 1% calcium grower diets are used a short period of time, and many producers do around the time of maturity, then these diets should not want the bother of handling an extra diet at not be used after the appearance of first egg, and the layer farm. There is also a reluctance by some to 0.5% production at the very latest. It must be producers with multi-age flocks, at one site, to remembered that under commercial conditions, use prelay diets where delivery of diets with 2% it is very difficult to precisely schedule diet calcium to the wrong flock on site can have dis- changes, and so decisions for diet change need astrous effects on production. to precede actual time of diet change, such that production does not reach 5 – 10% before Simply in terms of calcium metabolism, the birds physically receive the calcium enriched diets. most effective management program is early introduction of the layer diet. Such high calci- Prelay diets provide more calcium than do um diets allow sustained production of even the most grower diets, but still not enough Ca for sus- earliest maturing birds. As previously men- tained production. Prelay diets should allow the tioned, higher calcium diets fed to immature birds, SECTION 3.3 Feeding management of growing pullets

152 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS lead to reduced percentage retention, although any adverse effect on kidney structure is seen (see absolute retention is increased (Table 3.33). following section on urolithiasis). It seems like- ly that the high levels of excreta calcium shown Feeding layer diets containing 3.5% calcium, in Table 3.33 reflect fecal calcium, suggesting that prior to first egg, therefore results in a slight excess calcium may not even be absorbed into increase in calcium retention of about 0.16 g/d the body, merely passing through the bird with relative to birds fed 0.9% calcium grower diets the undigested feed. This is perhaps too simplistic at this time. Over a 10 d period, however, this a view, since there is other evidence to suggest increased accumulation is equivalent to the that excess calcium may be absorbed by the imma- output in 1 egg. Since there is only about 1 g of ture bird at this time. Such evidence is seen in mobile medullary calcium reserve in the mature the increased water intake of birds fed layer bird, then the calcium retention values shown diets prior to maturity (Figure 3.7). in Table 3.33 suggest accumulation of some cortical bone at this time. Early introduction of a high calcium layer diet seems to result in increased water intake, and a Early introduction of layer diets is therefore resultant increase in excreta moisture. an option for optimizing the calcium retention Unfortunately this increased water intake and wet- of the bird. However, there has been some ter manure seems to persist throughout the lay- criticism leveled at this practice. There is the argu- ing cycle of the bird, (Table 3.34). These data sug- ment that feeding excess calcium prior to lay gest that birds fed high calcium layer diets imposes undue stress on the bird’s kidneys, during the prelay period will produce manure that since this calcium is in excess of her immediate contains 4 – 5% more moisture than birds fed 1% requirement and must be excreted. In the study calcium grower or 2% calcium prelay diets. detailed in Table 3.33, there is increased excreta There are reports of this problem being most pro- calcium. However, kidney histology from these nounced under heat stress conditions. A 4-5% birds throughout early lay revealed no change increase in manure moisture may not be prob- due to prelay calcium feeding. Recent evi- lematic under some conditions, although for those dence suggests that pullets must be fed a layer farms with a chronic history of wet layer manure, diet from as early as 6 – 8 weeks of age before this effect may be enough to tip the balance and Table 3.33 Effect of % diet calcium fed to birds immediately prior to lay on calcium retention Diet Ca (%) Daily Ca Excreta Ca retention (g) (% dry matter) 0.9 1.5 0.35 1.4 2.0 0.41 3.0 2.5 0.32 5.7 3.0 0.43 5.9 3.5 0.41 7.5 0.51 7.7 SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 153 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Fig. 3.7 Effect of introducing a 4% calcium layer diet at 112 days ( _____ ) and at 138 ( _ _ _ _ ) on daily water intake. Table 3.34 Effect of prelay calcium level on excreta moisture (%) Prelay diet Ca (%) Bird age (d) (16 – 19 weeks)1 147 175 196 245 65.5 1.0 71.4 78.7 75.3 63.9 63.9 2.0 71.6 77.2 73.9 69.4 3.0 72.1 77.7 74.1 4.0 77.0 80.0 76.0 1 All birds fed 4.0% Ca after 20 weeks of age produce a problem. The current trend of feeding manure may be a problem, a 2% calcium prelay even higher calcium levels to laying hens may accen- diet is recommended. There seems to be no prob- tuate this problem, and so dictate the need for prelay lem with the use of 2% calcium prelay diets, as diets with more moderate levels of calcium. long as birds are consuming a high calcium layer diet no later than at 1% egg production. In summary, the calcium metabolism of the earliest maturing birds in a flock should be the ii) Prelay body weight and composition – criterion for selection of calcium levels during Prelay diets are often formulated and used on the the prelay period. Prolonged feeding of low-cal- assumption that they will improve body weight cium diets is not recommended. Early introduction and/or body composition, and so correct problems of layer diets is ideal, although where wet arising with the prior growing program. Body weight SECTION 3.3 Feeding management of growing pullets

154 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS and body condition should not really be considered of the limitations in the use of high nutrient dense in isolation, although at this time, we do not have prelay diets. a good method of readily assessing body con- dition in the live pullet. For this reason our main While body composition at maturity may emphasis at this time is directed towards well be as important as body weight at this age, body weight. it is obviously a parameter that is difficult to quantitate. There is no doubt that energy is like- Pullet body weight is the universal criterion ly the limiting nutrient for egg production of all used to assess growing program. Each strain of strains of bird, and at peak egg numbers, feed may bird has a characteristic mature body weight that not be the sole source of energy. Labile fat must be reached or surpassed for adequate egg reserves seem essential to augment feed sources production and egg mass output. In general, prelay that are inherently limited by low feed intake. These diets should not be used in an attempt to manip- labile fat reserves become critical during situations ulate mature body size. The reason for this is that of heat stress or general hot weather conditions. for most flocks, it is too late at this stage of Once the bird starts to produce eggs, then its abil- rearing to meaningfully influence body weight. ity to build fat reserves is greatly limited. Obviously, if labile fat reserves are to be of significance, However, if underweight birds are necessarily then they must be deposited prior to maturity. As moved to a layer house, then there is perhaps with most classes of bird, the fat content of the pul- a need to manipulate body weight prior to let can best be manipulated through changing the maturity. With black-out housing, this can energy:protein balance of the diet. If labile fat some-times be achieved by delaying photo- reserves are thought necessary, then high energy, stimulation – this option is becoming less use- high fat prelay diets should be considered. As pre- ful in that both Leghorns and brown egg strains viously stated, this scenario could well be ben- are maturing early without any light stimulation. eficial if peak production is to coincide with If prelay diets are used in an attempt to correct periods of high environmental temperature. rearing mismanagement, then it seems as though the bird is most responsive to energy. This fact The requirement for a specific body com- fits in with the effect of estrogen on fat metab- position at the onset of maturity has not been ade- olism, and the significance of fat used for liver quately established. With mammals, onset and and ovary development at this time. While using function of normal estrus activity is dependent high nutrient density prelay diets may have a minor on attainment of a certain body fat content. In effect in manipulating body weight, it must be humans, for example, onset of puberty will not remembered that this late growth spurt (if it occurs) occur if body fat content is much less than will not be accompanied by any meaningful 14%. No such clear cut relationship has emerged change in skeletal growth. This means that in with egg layers. Work conducted with broiler extreme cases, where birds are very light weight breeders, in fact, indicates a more definite rela- and of small stature at say, 16 weeks of age, then tionship between lean body mass and maturity, the end result of using high nutrient dense rather than fat content and maturity. prelay diets may well be pullets of correct body weight, but of small stature. Pullets with a iii) Early egg size – Egg size is greatly influ- short shank length seem more prone to pro- enced by the size of the yolk that enters the oviduct. lapse/pick-out, and so this is another example In large part this is influenced by body weight SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 155 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS of the bird and so factors described previously nutrient dense diet at the time of sexual matu- for mature body weight can also be applied to rity. This somewhat unorthodox program is concerns with early egg size. There is a gener- designed to ‘pause’ the normal maturation pro- al need for as large an early egg size as is pos- cedure, and at the same time to stimulate greater sible. Most attempts at manipulating early egg egg size when production resumes after about size have met with limited success. Increased 10-14 days. This type of prelay program is levels of linoleic acid in prelay diets may be of therefore most beneficial where early small egg some use, although levels in excess of the usual size is economically undesirable. 1% found in most diets produce only marginal effects on early egg size. From a nutritional stand- Pre-pause can be induced by simply with- point, egg size can best be manipulated with diet drawing feed, usually at around 1% egg pro- protein, and especially methionine concentra- duction. Under these conditions, pullets imme- tion. It is logical, therefore to consider increas- diately lose weight, and fail to realize normal ing the methionine levels in prelay diets. weight-for-age when refed. Egg production and feed intake normalize after about 4 weeks, iv) Pre-pause – In some countries, and most notably although there is 1-1.5 g increase in egg size. Japan, pre-pause feeding programs are used to Figure 3.8 shows the production response of maximize early egg size. The idea behind these Leghorn pullets fed only wheat bran from 18 weeks programs is to withdraw feed, or feed a very low (or 1% egg production) through to 20 weeks of age. Fig. 3.8 Early egg production of pullets fed wheat bran at 1% egg production or at 18 weeks of age. SECTION 3.3 Feeding management of growing pullets

156 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS The most noticeable effects resulting from use Because diet electrolytes can influence water of a pre-pause diet such as wheat bran, are a very balance and renal function, it is often assumed rapid attainment of peak egg production and an that electrolyte excess or deficiency may be increase in egg size once refeeding commences. predisposing factors in urolithiasis or gout. This management system could therefore be Because salts of uric acid are very insoluble, then used to better synchronize onset of production the excretion of precipitated urate salts could serve (due to variance in body weight), to improve early as a water conservation mechanism, especial- egg size or to delay production for various man- ly when cations are excreted during salt loading agement related decisions. The use of such or when water is in short supply. When roost- pre-pause management will undoubtedly be ers are given saline water (1% NaCl) and fed high affected by local economic considerations, and protein diets, uric acid excretion rates are dou- in particular the price of small vs. medium vs. bled compared to birds offered the high protein large grade eggs. diet along with non-saline drinking water. Because uric acid colloids are negatively charged, v) Urolithiasis – Kidney dysfunction often leads they attract cations such as Na, and so when these to problems such as urolithiasis that some-times are in excess, there is an increased excretion via occurs during the late growing phase of the urates, presumably at the expense of conventional pullet or during early egg production. While infec- NH4 compounds. There is some evidence of an tious bronchitis can be a confounding factor, imbalance of Na+K:Cl levels influencing kidney urolithiasis is most often induced by diet min- function. When excess Na+K relative to Cl is fed, eral imbalance in the late growing period. At post- a small percentage of the birds develop urolithi- mortem, one kidney is often found to be enlarged asis. It is likely that such birds are excreting a and contain mineral deposits known as uroliths. more alkaline urine, a condition which encour- Some outbreaks are correlated with a large ages mineral precipitation and urate formation. increase in diet calcium and protein in layer vs. grower diets, coupled with the stress of physically As previously described, Urolithiasis occurs moving pullets at this time, and being subject- more frequently in laying hens fed high levels of ed to a change in the watering system (usually calcium well in advance of sexual maturity. onto nipples in the laying cages). The uroliths Feeding prelay (2-2.5% Ca) or layer diets con- are most often composed of calcium-sodium-urate. taining 4-5% calcium for 2-3 weeks prior to first egg is usually not problematic, and surprising- The occurrence is always more severe when ly, uroliths rarely form in adult male breeders fed immature pullets are fed high calcium diets for high calcium diets. High levels of crude protein an extended period prior to maturity. For exam- will increase plasma uric acid levels, and poten- ple, urolithiasis causing 0.5% weekly mortali- tially provide conditions conducive to urate ty often occurs under experimental conditions formation. when pullets are fed layer diets from 10-12 weeks of age (relative to maturity at 18-19 In humans, urolith formation (gout) can be weeks). However, there is no indication that early controlled by adding urine acidifiers to the diet. introduction of a layer diet for just 2-3 weeks prior Studies with pullets show similar advantages. to maturity is a causative factor. Adding 1% NH4Cl to the diet results in a more SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 157 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS acidified urine, and uroliths rarely form under can be minimized by not oversupplying nutri- these conditions. Unfortunately, this treatment ents such as calcium, crude protein and electrolytes results in increased water intake, and associat- for too long a period prior to maturity. ed wet manure. One of the potential prob- lems in using NH4Cl once the birds start laying g) Lighting programs is that the metabolic acidosis is detrimental to eggshell quality especially under conditions of Photoperiod has a dramatic influence on the heat stress. Such treatment also assumes the kid- growth and body composition of the growing pul- ney can clear the increased load of H+, and for let and so light programs must be taken into a damaged kidney, this may not always be pos- account when developing feeding programs. In sible. As a potential urine acidifier without terms of pullet management, day length has two such undesirable side effects, several researchers major effects, namely the development of repro- have studied the role of Alimet® a methionine ductive organs and secondly a change in feed intake. analogue. In one study, pullets were fed diets con- It is well known that birds reared on a step-up or taining 1 or 3% calcium with or without Alimet® naturally increasing day length will mature ear- from 5-17 weeks. Birds fed the 3% calcium diet lier than those reared on a constant day length. excreted alkaline urine containing elevated cal- Similarly, if birds are subjected to a step-down day cium concentrations together with urolith formation length much after 12 weeks of age, they will and some kidney damage. Feeding Alimet® acid- likely exhibit delayed sexual maturity. The longer ified the urine, but did not cause a general the photoperiod, the longer the time that birds have metabolic acidosis. Alimet® therefore reduced to eat feed, and so usually this results in heavier kidney damage and urolith formation without caus- birds. Table 3.35 shows the growth rate and ing acidosis or increased water consumption. feed intake of pullets reared on constant day Urine acidification can therefore be used as a pre- lengths of 6, 8, 10 or 12 hours to 18 weeks of age. vention or treatment of urolithiasis, and this For Leghorn pullets, each extra hour of day length can be accommodated without necessarily during rearing increased body weight by about 20 inducing a generalized metabolic acidosis. g and feed intake by 100 g. For brown egg pul- From a nutritional viewpoint, kidney dysfunction lets there was a 13 g increase in weight and 70 g increase in feed intake for each hour of extra light. Table 3.35 Effect of day length during rearing on growth and feed intake of pullets Hours of Leghorn Brown egg light/d 7d-18 wks 18 wk Feed 17 wk egg 18 wk Feed 17 wk egg wt (g) intake production wt (g) intake production 6 8 1328c (kg) (%) 1856b (kg) (%) 10 1376b 1930ab 12 1425a 6.14 0 1889ab 7.53 12 1455a 1953a 6.00 1.2 7.83 12 6.30 2.0 7.60 10 6.71 3.4 8.06 12 SECTION 3.3 Feeding management of growing pullets

158 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Longer photoperiods may be beneficial in hot eggshell deformation). The reason for improved weather situations where feed intake of pullets shell quality is not clear, although we have seen is often depressed. As the day length for the grow- this with other flocks that fail to show adequate ing pullet is increased, there is a reduction in age sustained peaks – maybe giving up a few eggs at at maturity. Research data suggests earlier matu- peak is a means of improving shell quality. The rity with constant rearing day lengths up to 16- increased egg size for birds on the constant 14 18 hours per day, although longer daylengths such h photoperiod is undoubtedly due to birds being as 20-22 hours per day seem to delay maturity. heavier at maturity, and then eating more feed Another potential problem with longer day throughout the laying period. length during rearing is that it allows less poten- tial for light stimulation when birds are moved to When birds are light stimulated prior to first laying facilities. However, in equatorial regions egg, their age at light stimulation will have an effect where maximum day length fluctuates between on age at first egg. Our data suggest that after98 11-13 hours, many birds are managed without d of age, for each 1 d delay in age at light stim- any light stimulation. In fact, under such hot weath- ulation, first egg will occur about 0.5 d later (Figure er, high light intensity conditions, excessive 3.9). This means that light stimulating a pullet stimulation often results in prolapse and blowouts. at 105 d rather than 125 d, will likely result in In these situations if light stimulation is given, it earlier maturity by about 10 days. At this time, should follow rather than lead, the onset of egg it is important to re-emphasize the previous production. It seems that for modern strains of discussion concerning adequacy of body weight birds, light stimulation at ‘maturity’ is not always and body condition before considering earlier necessary for adequate layer performance. In a light stimulation. Another program that can be recent trial, we have shown some advantages to used to stimulate growth is ‘step-down’ lighting constant 14 h photoperiods for the entire life of (Figure 3.10). the bird vs. an 8 h rearing photoperiod followed by a 14 h layer photoperiod (Table 3.36). Pullets In Figure 3.10, birds are given 23 hr light/d for that were grown on constant 14 h light and not the first week and then day length is reduced by given any extra day length at maturity produced about 1 h each week until 10 h per day is fewer eggs mainly due to reduced peak pro- achieved, at which time it is held constant. When duction. However, this flatter peak was associ- birds are in open-sided houses, the minimum day ated with a significant increase in egg size and length achieved is dictated by the maximum a significant improvement in shell quality (lower natural day length during this time. Birds can then Table 3.36 Effect of rearing daylength on subsequent layer performance Photoperiod 336d egg Egg weight Shell deformation production (g) (µg) Rearing Laying 58.4b 26.5a 271a 8h 14h 60.3a 25.4b 256b 14h 14h SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 159 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Fig. 3.9 Age at light stimulation (8-14 hr) and sexual maturity. Fig. 3.10 Step-down lighting. SECTION 3.3 Feeding management of growing pullets

160 CHAPTER 3 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS be photostimulated at the normal time. The step- now maturing very early and since their mature down program has the advantage of allowing the body size has been decreased, the need for pullets to eat feed for considerably more time each restriction occurs less frequently. A major con- day during their early development. In hot cern with restriction programs is maintenance of weather conditions, this long day length means flock uniformity. With a mild restriction program, that birds are able to eat more feed during cool- birds can be allowed to ‘run-out’ of feed one day er parts of the day. The system should not be con- per week and usually this will do little harm to fused with historical step-down lighting pro- uniformity. If it is necessary to impose a greater grams that continued step-down until 18-20 degree of feed restriction on a daily basis, then weeks; these older programs were designed to delay it is important to ensure rapid and even feed dis- maturity. For the program in Figure 3.10, matu- tribution, as subsequently discussed for broiler rity will not be affected as long as the step-down breeders (Chapter 5). Feed restriction should be regime is stopped by 10 – 12 weeks of age, i.e. relaxed if birds are subjected to any stresses before the pullet becomes most sensitive to such as beak trimming, vaccination, general changes in day length. The step-down lighting pro- disease challenges or substantial reduction in envi- gram is one of the simplest ways of increasing growth ronmental temperature. An alternative man- rate in pullets and is practical with both blackout agement procedure for overweight birds is to sched- and open-sided buildings. ule an earlier light stimulation and move to layer cages (see Figure 3.4). Keshavarz (1998) shows increased body weight of 15 week old pullets grown on a step-down Brown egg pullets do seem to consume less lighting program of 23 to 8 h by 16 weeks (Table 3.37). energy and so are smaller when given lower ener- In this study the step-down photoperiod was con- gy diets. For example providing pullets grow- tinued through to 16 weeks, and this delayed sex- er-developer diets at 2750 vs. 3030 kcal ME/kg ual maturity resulting in a 1 g increase in egg size. resulted in an 8% reduction in energy intake and 4% reduction in body weight. These same diets h) Feed restriction fed to Leghorn pullets resulted in just 4% reduc- tion in energy intake of the lower energy diet with Feed restriction may be necessary for controlling virtually no change in body weight. Reduced nutri- the weight of brown egg pullets during cooler win- ent density should therefore be considered in con- ter months. The goal of any restriction program junction with physical feed restriction, for con- is to ensure optimum weight-for-age at sexual matu- trolled growth of brown egg pullets. rity. Because many strains of brown egg birds are Table 3.37 Effect of continuous weekly step-down lighting on pullet development Rearing Body wt 18 wk Feed intake Age first egg photoperiod (15 wk) (g) uniformity (%) (0-18 wk) (kg) (d) 8h 1070a 69 5.98 130 23 to 8 h @ 16 wk1 1120b 78 6.20 140 11 hour decrease/wk Adapted from Keshavarz (1998) SECTION 3.3 Feeding management of growing pullets

CHAPTER 3 161 FEEDING PROGRAMS FOR GROWING EGG-STRAIN PULLETS Suggested Readings Leeson, S., J.D. Summers and L.J. Caston, (1993). Growth response of immature brown egg strain pul- Keshavarz, K. (1998). The effect of light regimen, lets to varying nutrient density and lysine. Poult. floor space and energy and protein levels during the Sci. 72:1349-1358. growing period on body weight and early egg size. Poult. Sci. 77:1266-1279. Leeson, S., J.D. Summers and L.J. Caston, (1998). Keshavarz, K. (2000). Re-evaluation of non-phytate Performance of white and brown egg pullets fed phosphorus requirement of growing pullets with varying levels of diet protein with constant sulfur and without phytase. Poult. Sci. 79:1143-1153. amino acids, lysine and tryptophan. J. Appl. Poult. Leeson, S. and J.D. Summers, (1985). Response of Res. 7:287-301. growing Leghorn pullets to long or increasing pho- toperiods. Poult. Sci. 64:1617-1622. Leeson, S., J.D. Summers and L.J. Caston, (2000). Leeson, S. and J.D. Summers, (1989). Performance Net energy to improve pullet growth with low pro- of Leghorn pullets and laying hens in relation to tein amino acid fortified diets. J. Appl. Poult. Res. hatching egg size. Can. J. Anim. Sci. 69:449-458. 9:384-392. Leeson, S. and J.D. Summers, (1989). Response of Leghorn pullets to protein and energy in the diet Lewis, P.D. and G.C. Perry, (1995). Effect of age at when reared in regular or hot-cyclic environments. sexual maturity on body weight gain. Br. Poult. Sci. Poult Sci. 68:546-557. 36:854-856. Leeson, S., (1986). Nutritional considerations of poultry during heat stress. World’s Poult. Sci. Martin, P.A., G.D. Bradford and R.M. Gous, (1994). 42:619-681. A formula method of determining the dietary amino Leeson, S., (1991). Growth and development of acid requirements of laying type pullets during their Leghorn pullets subjected to abrupt changes in envi- growing period. Br. Poult. Sci. 35:709-724. ronmental temperature and dietary energy level. Poult. Sci. 70:1732-1738. Patterson, P.H. and E.S. Lorenz, (1997). Nutrients in Leeson, S. and L.J. Caston, (1993). Does environmen- manure from commercial White Leghorn pullets. J. tal temperature influence body weight; shank length Appl. Poult. Res. 6:247-252. in Leghorn pullets? J. Appl. Poult. Res. 2:253-258. Summers, J.D. and S. Leeson, (1994). Laying hen performance as influenced by protein intake to six- teen weeks of age and body weight at point of lay. Poult. Sci. 73:495-501. SECTION 3.3 Feeding management of growing pullets



4CHAPTER FEEDING PROGRAMS 163 FOR LAYING HENS Page 4.1 Diet specifications and formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .164 4.2 Feed and energy intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170 4.3 Problems with heat distress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177 a. Bird’s response to heat stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179 b. Maintaining energy balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182 c. Protein and amino acids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 d. Minerals and vitamins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184 e. Electrolyte balance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185 f. Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 g. Effect of physical diet change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188 h. Summary of nutritional management during heat . . . . . . . . . . . . . . . . . .189 4.4 Phase Feeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .190 4.5 Formulation changes and feed texture . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192 4.6 Nutrition and shell quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193 4.7 Controlling egg size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .198 4.8 Diet and egg composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203 4.9 Diet involvement with some general management problems . . . . . . . . . . . . .214 4.10 Nutrient management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222

164 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS 4.1 Diet specifications and formulations D iet specifications for laying hens are diet or as a ratio to energy, decline as the bird shown in Table 4.1, and are catego- progresses through the laying cycle. In order to rized according to age and feed intake. sustain shell quality, it is important to increase There is no evidence to suggest that the energy level diet calcium level, and to concomitantly decrease of diets needs to be changed as the birds progress diet phosphorus level, as the bird gets older. The through a laying cycle. The layer’s peak energy need for less methionine is partially related to the needs are most likely met at around 35 weeks of need for tempering late-cycle increase in egg size, age, when production and daily egg mass output since this is usually uneconomical regarding egg are maximized. However, the layer quite precisely pricing and larger eggs have thinner shells. adjusts its intake according to needs for energy and There is little evidence for change in needs for so variable energy needs are accommodated by vitamins and trace minerals as birds get older, and change in feed intake. so a single premix specification is shown in Table 4.1. For most of the B-vitamins, it is pos- Most Leghorn strains will now commence egg sible to phase feed with up to 30% reduction by production with feed intakes as low as 80 – 85 the end of the laying cycle. g/day, and it is difficult to formulate diets for such a small appetite. For brown egg strains, initial Examples of layer diets using corn, wheat, or feed intake will be around 92 - 95 g/day and so sorghum as the main energy source and with or formulation is more easily accommodated. For without meat meal, are shown in Tables 4.2 – 4.5. all diets, maintaining the balance of all nutrients The diets are categorized according to age of bird. to energy is the most important consideration dur- It is difficult to achieve desired energy level in ing formulation. Phase I diets (Table 4.2) without resorting to inclu- sion of significant quantities of fat. If fat supply In general terms, diet nutrient concentrations and quality is questionable, it may be advisable decrease over time, with the notable excep- to reduce the energy level of the diet (and also tion of the need for calcium. Thus, diet protein all other nutrients in the same ratio), by up to 50 and amino acids expressed as a percent of the – 70 kcal ME/kg. SECTION 4.1 Diet specifications and formulations

CHAPTER 4 165 FEEDING PROGRAMS FOR LAYING HENS Table 4.1 Diet specifications for layers Approximate age 18-32 wks 32-45 wks 45-60 wks 60-70 wks Feed intake (g/bird/day) 100 105 100 110 Crude Protein (%) 90 95 95 100 Metabolizable Energy (kcal/kg) 17.5 16.5 16.0 15.0 Calcium (%) 20.0 19.0 19.0 18.0 2850 2850 2800 2800 Available Phosphorus (%) Sodium (%) 2900 2900 2875 2875 4.5 4.3 4.6 4.4 Linoleic acid (%) 0.38 0.36 0.33 0.31 Methionine (%) 4.2 4.0 4.4 4.2 0.16 0.15 0.16 0.15 Methionine + Cystine (%) 1.3 1.2 1.2 1.1 Lysine (%) 0.50 0.48 0.43 0.4 0.39 0.37 0.34 0.32 Threonine (%) 0.67 0.64 0.6 0.57 Tryptophan (%) 0.18 0.17 0.17 0.16 0.78 0.74 0.73 0.69 Arginine (%) 0.60 0.57 0.55 0.52 Valine (%) 1.8 1.7 1.5 1.4 0.16 0.15 0.15 0.14 Leucine (%) 0.77 0.73 0.74 0.70 Isoleucine (%) 0.45 0.43 0.41 0.39 0.67 0.64 0.63 0.60 Histidine (%) 0.43 0.41 0.40 0.38 Phenylalanine (%) 0.75 0.71 0.70 0.67 0.58 0.55 0.53 0.50 0.13 0.12 0.12 0.11 Vitamins (per kg of diet): 0.86 0.82 0.80 0.76 0.44 0.42 0.41 0.39 Vitamin A (I.U) Vitamin D3 (I.U) 0.69 0.66 0.64 0.61 Vitamin E (I.U) Vitamin K (I.U) 0.18 0.17 0.17 0.16 Thiamin (mg) Riboflavin (mg) 0.88 0.84 0.82 0.78 Pyridoxine (mg) Pantothenic acid (mg) 0.77 0.73 0.72 0.68 Folic acid (mg) Biotin (µg) 0.53 0.50 0.48 0.46 Niacin (mg) Choline (mg) 0.68 0.65 0.63 0.60 Vitamin B12 (µg) 0.17 0.16 0.15 0.14 Trace minerals (per kg of diet): Manganese (mg) 0.52 0.49 0.48 0.46 Iron (mg) Copper (mg) 8000 Zinc (mg) 3500 Iodine (mg) Selenium (mg) 50 3 2 5 3 10 1 100 40 400 10 60 30 5 50 1 0.3 SECTION 4.1 Diet specifications and formulations

166 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Table 4.2 Examples of Phase 1 layer diets (18-32 wks) 1 2 3 4 56 507 554 Corn 517 619 440 373 Wheat 327 70 68 184 Sorghum 45 245 42 70 70 Wheat shorts 31 171 311 214 Meat meal 1.2 261 40 60 59 Soybean meal 3.6 1.2 60 Fat 99.5 2.6 1.5 1.8 1.8 DL-Methionine* 15.7 92.3 1.6 2.0 3.6 2.6 Salt 1 2.9 3.0 94 100 93 Limestone 1000 1 100 1.5 14.6 1.6 Dical Phosphate 1000 14.4 1 1 1 Vit-Min Premix** 1 1000 1000 1000 1000 Total (kg) 20 20 20 20 20 20 Crude Protein (%) 2900 2900 2900 2900 2900 2900 ME (kcal/kg) Calcium (%) 4.2 4.2 4.2 4.2 4.2 4.2 Av Phosphorus (%) 0.5 0.5 0.5 0.5 0.5 0.5 Sodium (%) 0.18 0.18 0.18 0.18 0.18 0.18 Methionine (%) 0.45 0.46 0.45 0.45 0.45 0.45 Meth + Cystine (%) 0.76 0.75 0.77 0.76 0.8 0.78 Lysine (%) 1.14 1.15 1.12 1.05 1.17 1.16 Threonine (%) 0.86 0.83 0.75 0.7 0.78 0.75 Tryptophan (%) 0.28 0.26 0.30 0.28 0.28 0.26 * or eqivalent MHA ** with choline SECTION 4.1 Diet specifications and formulations

CHAPTER 4 167 FEEDING PROGRAMS FOR LAYING HENS Table 4.3 Examples of Phase 2 layer diets (32-45 wks) Corn 1 2 3 4 5 6 Wheat 536 581 Sorghum 586 508 419 382 Wheat shorts 301 70 118 200 Meat meal 39 220 8 123 65 Soybean meal 24.6 60 279 192 Fat 0.9 233 156 60 56 DL-Methionine* 3.3 1.1 50 50 Salt 106 2.3 1.5 1.5 Limestone 12.8 100 1.3 1.2 3.4 2.5 Dical Phosphate 1 2.7 1.8 107 100 Vit-Min Premix** 1000 1 107 99 11.1 1000 11.0 1 1 Total (kg) 1 1 1000 1000 1000 1000 Crude Protein (%) 19 19 19 19 19 19 ME (kcal/kg) 2875 2875 2875 2875 2875 2875 Calcium (%) Av Phosphorus (%) 4.4 4.4 4.4 4.4 4.4 4.4 Sodium (%) 0.43 0.44 0.43 0.44 0.43 0.44 Methionine (%) 0.17 0.17 0.17 0.17 0.17 0.17 Meth + Cystine (%) 0.41 0.42 0.41 0.41 0.41 0.41 Lysine (%) 0.70 0.70 0.72 0.70 0.74 0.72 Threonine (%) 1.07 1.07 1.04 1.04 1.08 1.09 Tryptophan (%) 0.82 0.79 0.71 0.67 0.74 0.71 0.26 0.25 0.28 0.26 0.26 0.25 * or eqivalent MHA ** with choline SECTION 4.1 Diet specifications and formulations

168 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Table 4.4 Examples of Phase 3 layer diets (45-60 wks) 1 2 3 456 626 Corn 584 60 Wheat 190 648 571 14.8 Sorghum 113 550 483 1.2 50 35 143 Wheat shorts 2 187 115 55 105 40 40 248 169 Meat meal 1.3 1.5 40.5 1 2.5 1.5 40 Soybean meal 261 1000 111 107 1.5 1.5 9.2 3.2 2.5 Fat 29 11 111 1000 1000 9.8 105 DL-Methionine* 1 1 1000 1 Salt 3 1000 Limestone 111 Dical Phosphate 10 Vit-Min Premix** 1 Total (kg) 1000 Crude Protein (%) 17.5 17.5 17.5 17.5 17.5 17.5 ME (kcal/kg) 2850 2850 2850 2850 2850 2850 Calcium (%) Av Phosphorus (%) 4.5 4.5 4.5 4.5 4.5 4.5 Sodium (%) 0.38 0.39 0.38 0.38 0.38 0.38 Methionine (%) 0.16 0.16 0.16 0.16 0.16 0.16 Meth + Cystine (%) 0.40 0.42 0.39 0.41 0.39 0.39 Lysine (%) 0.67 0.67 0.67 0.67 0.70 0.68 Threonine (%) 0.95 0.95 0.92 0.93 0.98 0.98 Tryptophan (%) 0.76 0.73 0.63 0.60 0.68 0.64 0.24 0.22 0.26 0.24 0.24 0.22 * or eqivalent MHA ** with choline SECTION 4.1 Diet specifications and formulations

CHAPTER 4 169 FEEDING PROGRAMS FOR LAYING HENS Table 4.5 Examples of Phase 4 layer diets (60-70 wks) 1 23 4 56 619 527 Corn 638 570 Wheat Sorghum 485 467 156 200 Wheat shorts 51 126 190 42 49 38 192 138 Meat meal 157 138 90 40 37 9.7 40 40 Soybean meal 221 1.2 1.4 1 1.1 1.2 3 2.6 Fat 13 2.3 2.4 1.8 115 111 110 115 111 6.8 DL-Methionine* 0.8 6.5 1 1 1 1 1 1000 1000 Salt 3 1000 1000 1000 Limestone 115 Dical Phosphate 8.2 Vit-Min Premix** 1 Total (kg) 1000 Crude Protein (%) 16 16 16 16 16 16 ME (kcal/kg) 2800 2800 2800 2800 2800 2800 Calcium (%) Av Phosphorus (%) 4.6 4.6 4.6 4.6 4.6 4.6 Sodium (%) 0.33 0.35 0.35 0.35 0.35 0.35 Methionine (%) 0.16 0.16 0.16 0.16 0.16 0.16 Meth + Cystine (%) 0.36 0.37 0.35 0.36 0.34 0.34 Lysine (%) 0.60 0.60 0.60 0.60 0.62 0.61 Threonine (%) 0.83 0.83 0.80 0.80 0.85 0.85 Tryptophan (%) 0.70 0.67 0.57 0.55 0.60 0.59 0.22 0.20 0.24 0.23 0.21 0.20 * or eqivalent MHA ** with choline SECTION 4.1 Diet specifications and formulations

170 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS 4.2 Feed and energy intake production. This situation leads to smaller eggs, and often lower than normal peak or birds drop- F eeding programs for layers cannot be ping relatively quickly in production shortly developed without consideration for the rear- past peak as discussed in the previous chapter. ing program as discussed in Chapter 3. Unfortunately, many egg producers purchase point- It takes a certain amount of feed to produce of-lay pullets from independent pullet grow- a laying hen with optimum body size. If this feed ers, and here the goals of the two producers are is not consumed in the growing period, it must not always identical. Too often the egg producer be fed in the laying house. Of course, one is interested in purchasing mature pullets at the would have to be sure that the pullets are healthy lowest possible cost per bird regardless of their and are not carrying an excess of body fat. condition. For pullet growers to make a profit However, the problem of excess body fat with they must produce birds at the lowest possible today’s modern type, early maturing pullet, does cost. With feed representing some 60 to 70% of not usually occur. Egg producers should also find the cost to produce a pullet, the obvious way for out as much as possible about the pullets they are the pullet grower to reduce costs is to save on purchasing, such as the type of feeding program feed cost. While they may be able to save a small they have been on, the health status of the flock, amount of feed by eliminating feed waste or by and the type of waterers used in rearing. With ensuring that house temperatures are optimum, this type of information, they should be in a the only way to save a substantial amount of feed better position to ensure a profitable laying flock. is to place the pullets on a growing program such that feed consumption is reduced and/or cheap- It is now common practice to describe feed- er diets are used. Because it is not possible to ing programs for layers according to the level of enhance the efficiency with which pullets con- feed intake. It is well known that under normal vert feed into body weight gain, the net result is environmental and management conditions, a smaller bird at time of transfer. If the birds have feed intake will vary with egg production and/or been on an increasing light pattern, they might age of bird, and this must be taken into account well be mature, as judged from appearance, at when formulating diets. While layers do adjust the onset of production. However, such pullets feed intake according to diet energy level, there must still grow before they reach their opti- is no evidence to suggest that such precision occurs mum weight and condition as a laying hen. with other nutrients. Consequently, the egg producer will have to feed this pullet in an attempt to bring the body weight The following daily intakes of nutrients are sug- up to normal if a profitable laying flock is to be gested under ideal management and environmental obtained. If egg producers attempt to save on feed, conditions (Table 4.6). the result will be underweight birds at peak egg SECTION 4.2 Feed and energy intake

CHAPTER 4 171 FEEDING PROGRAMS FOR LAYING HENS Table 4.6 Daily nutrient needs for Leghorn birds. Age (wks) 18 – 32 32 – 45 45 – 60 60 – 70 20 16 Protein (g) 260 18.5 17.5 280 Metabolizable energy (kcal) 4.0 4.6 Calcium 550 290 285 Av. Phosphorus (g) 500 330 Methionine (mg) 4.2 4.4 340 TSAA (mg) 830 600 Lysine (mg) 950 450 380 730 (mg) 430 390 740 670 840 780 Table 4.7 Feed intake of Leghorns as influenced by body weight, egg production, egg weight and environmental temperature1 Body weight Egg production Egg weight Temperature Egg production Intake Egg wt Intake ºC Intake Body wt Intake (%) (g/d) (g) (g/d) (g/d) (g) (g/d) 98 100.5 50 90.8 10 102.2 94 98.8 55 94.0 15 102.1 1200 92.7 90 97.1 60 97.1 20 97.1 86 95.4 65 100.3 25 92.1 1250 94.9 82 93.8 70 103.4 30 87.1 1300 97.1 2.4% 1 g 1.6 g 1 g 1ºC 1 g 1350 99.3 1400 101.5 23g 1 g 1 Assumes 1300 g body weight, 90% egg production, 60 g egg weight and 20 C as the standard, with diet at 2850 kcal/kg At any given time, it is necessary to adjust diet It is possible to predict energy needs, and hence specifications according to the actual feed intake feed intake, based on knowledge of the major of the flock. Within a single strain it is possible variables. The equation most commonly used to see a ± 15 g variance in feed intake at any age is described below. Using this equation, Table related to stage of maturity, egg mass, body 4.7 was developed with variable inputs of body size and most importantly, environmental tem- weight, egg production, egg weight and envi- perature. ronmental temperature. Feed intake was calculated assuming a diet energy level of 2850 kcal ME/kg. Energy (kcal ME/bird/day) = [Body weight (kg)] [170 – 2.2 x ºC] + [2 x Egg mass/d (g)] + [5 x Daily weight gain (g)] SECTION 4.2 Feed and energy intake

172 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS For these calculations, one factor at a time was high vs. low body weight etc. should be accom- changed, and the standards for other parameters modated in diet formulation. are highlighted across the middle of Table 4.7. For example, in the case of body weight, the effect A knowledge of feed intake, and the factors on feed intake was calculated with 50 g incre- that influence it, are therefore essential for any ments of weight from 1200 to 1400 g. For each feed management program. To a degree, the ener- of these calculations for body weight, egg pro- gy level of the diet will influence feed intake, duction was fixed at 90%, egg weight at 60 g and although one should not assume the precision environmental temperature at 20˚C. Likewise, of this mechanism to be perfect. In general, birds when egg production was the variable considered over consume energy with higher energy diets, all other factors remained constant. The summary and they will have difficulty maintaining normal data appearing as the last row in Table 4.7 show energy intake when diets of less than 2500 kcal the relative change in each input parameter nec- ME/kg are offered. In most instances, under- con- essary to change feed intake by one gram/bird/day. sumption rather than over-consumption is the prob- Consequently, ± 23 g body weight, ± 2.4% egg lem, and so use of higher energy diets during sit- production, ±1.6 g egg weight, and ± 1ºC all change uations such as heat stress will help to minimize feed intake by ± 1 g/bird/day. Of these factors envi- energy insufficiency. Table 4.8 shows the ronmental temperature is usually the most vari- Leghorn bird’s response to variable diet energy. able on a day-to-day basis, and so, is likely responsible for most of the variation in feed These Leghorn strain birds performed sur- intake seen in commercial flocks. prisingly well with the diluted diets, and showed an amazing ability to adjust feed intake as diet With variable feed intake, it is necessary to nutrient density changed, and down to 2600 adjust the ratios of nutrients to energy to main- kcal ME/kg were able to maintain almost constant tain constant intakes of these nutrients. While energy intake. Only at 2450 kcal/kg, which it is impractical to consider reformulation based represents a 15% dilution of the original diet, were on day-to-day fluctuation in environmental tem- there indications of failure to consume ade- perature, trends in feed intake associated with quate amounts of energy (or other nutrients?). Table 4.8 Layer response to diet dilution (19 - 67 wks age) Diet Feed intake (g/b/d) Feed (kg) Egg Energy energy _____________________ ____________ ___________________ intake (kcal/kg)1 43 51 65 (19 – 67 wk) Number Mass (Mcal/365d) wks wks wks (kg) 33.9b 98.3 2900 100b 103bc 103b 34.3b 290 17.9a 94.7 37.1a 96.8 2750 100b 103bc 103b 37.1a 294 16.9b 91.2 2600 116a 113a 109ab 304 17.9a 2450 112a 111a 115a 302 17.3ab 1 All other nutrients in same ratio to energy across all diets Adapted from Leeson et al. (2001) SECTION 4.2 Feed and energy intake

CHAPTER 4 173 FEEDING PROGRAMS FOR LAYING HENS These birds were maintained at 20 - 22˚C, and requirement for nitrogen or non-essential amino it is suspected that the layers may have had dif- acids and/or that our assessment of essential amino ficulty maintaining nutrient intake with the dilut- acid needs are incorrect. As crude protein level ed diets if any heat distress conditions occurred. of the diet is reduced, regardless of amino acid supply, there is also increase in mortality and The diet specifications listed in Table 4.1 show reduced feather score (Table 4.9). The feather- values for crude protein. If soybean meal and ing of white and especially brown egg birds is corn, wheat or sorghum make up 60 – 70% of adversely affected by low protein diets (lower score). the diet, then protein per se gives an indication of the likely adequacy of amino acid needs. There is little doubt that body weight at Obviously formulation to total and digestible amino maturity is a major factor influencing feed intake acids is critical in more precisely meeting the bird’s of laying hens. Body weight differences seen at nutrient needs, yet there is still a need for other maturity are maintained throughout lay almost nitrogen containing nutrients that are variably regardless of nutrient profile of layer diets. It is described as crude protein or non-essential therefore difficult to attain satisfactory nutrient amino acids. Theoretically, a layer diet has to pro- intakes with small birds. Conversely, larger vide only the ten essential amino acids and birds will tend to eat more, and this may become under ideal conditions, these will be at require- problematic in terms of the potential for obesi- ment levels. However, when diets are formulated ty and/or too large an egg towards end of lay. Phase on this basis, production, and economic returns feeding of nutrients can overcome some of are reduced, suggesting the need for a ‘minimal’ these problems, although a more simplistic level of crude protein. Under commercial con- long-term solution is control over body weight ditions, production goals are rarely achieved when at maturity. Under most economic conditions, crude protein levels much less than 15% are used ‘heavier’ birds at maturity are ultimately most eco- through the layer cycle regardless of the supply nomical for table egg production in terms of egg of essential amino acids. Such effects imply a revenue relative to feed costs. Table 4.9 Effect of crude protein on mortality and feather score Feather score (Scale 0-20) %CP %Cannibalism White Brown 11.1 17.6 12.5 8.3 12.4 10.7 13.8 5.1 15.2 2.7 13.7 11.3 16.5 4.2 17.9 0.4 13.9 12.8 19.3 2.5 15.0 13.1 14.8 14.1 14.9 14.6 15.9 15.0 Adapted from Ambrosen and Petersen (1997) SECTION 4.2 Feed and energy intake

174 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Feed management becomes even more crit- tively, and relate these to the required intake of ical with earlier and higher sustained peak egg a standard diet. production from today’s strains of bird. Energy insufficiency during pre-peak production can cause The significance of energy intake as the lim- problems during post-peak production. Egg iting nutrient for egg production with modern strains production curves that show a 5 – 8% reduction of layer is shown in Figure 4.1. There is a dra- after peak are characteristic of birds with insuf- matic response to energy intake from 184 – 312 ficient appetite caused by too small a pullet at kcal/bird/day, in the form of egg output. At maturity (Figure 3.1). The reduction in appetite very high energy intakes, there is little apparent is of concern relative to the adequacy of ener- response to protein intake over the range of gy intake. Calculations of energy balance indi- 13 – 21 g/bird/day. Only when energy intake is cate a somewhat precarious balance around limiting is there any measurable increase in the time of peak egg numbers, emphasizing egg numbers in response to increased protein the need for stimulating feed intake and the intake. However, as will be detailed later possibility of providing some labile energy (Figure 4.13), the converse applies in terms of reserves in the form of carcass energy (fat) stores. egg size, when the bird shows a dramatic Tables 4.10 and 4.11 show such calculated val- response to protein intake, and little response to ues for Leghorn and brown egg strains respec - energy intake. Table 4.10 Energy balance of leghorn pullets during early egg production Theoretical Daily Energy Requirement Required intake of 17% CP, 2850 ME Age (kcal ME per bird) (wks) diet (g/d) Maintenance Growth Eggs Total 62 16 64 17 133 40 177 65 18 67 19 137 40 181 70 20 73 21 142 40 186 80 22 85 23 150 35 5 190 90 24 91 25 154 35 10 199 92 26 93 27 154 30 24 208 94 28 95 29 154 30 44 228 96 30 154 25 57 242 154 25 78 257 155 20 85 260 155 18 87 262 158 15 92 265 158 15 95 268 160 13 97 270 161 12 100 273 SECTION 4.2 Feed and energy intake

CHAPTER 4 175 FEEDING PROGRAMS FOR LAYING HENS Table 4.11 Energy balance of brown egg pullets during early egg production Theoretical Daily Energy Requirement Required intake of 17% CP, 2850 ME Age (kcal ME per bird) (wks) diet (g/d) Maintenance Growth Eggs Total 70 16 72 17 148 50 2 200 75 18 80 19 148 50 8 205 85 20 87 21 134 50 30 214 92 22 95 23 138 40 50 228 96 24 97 25 142 40 60 242 98 26 99 27 148 30 70 248 100 28 101 29 152 30 80 262 102 30 155 25 95 271 160 25 96 274 164 15 97 276 166 15 98 279 168 15 99 282 173 12 100 285 175 12 101 288 176 12 102 290 Fig. 4.1 Egg production (18-66 weeks) in response to daily intakes of energy and protein. SECTION 4.2 Feed and energy intake

176 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Many problems associated with marginal nutri- An argument against being overly concerned ent intake of young layers can most often be over- about uniformity, is that birds will adjust their come by ensuring optimum body weight and intake according to nutrient (energy) needs, and appetite of young laying pullets. Unfortunately, so early maturing birds will eat more, and late matur- mean weight of the flock at this age, is too ing birds less, during the early phases of produc- often considered independently of flock uniformity. tion. However, if birds are given diets formulat- Pullets may be of ‘mean’ body weight, yet be quite ed based on feed intake, this can lead to problems, variable in weight, and often outside the accept- the most serious of which is overfeeding of the larg- ed range of 85% of the flock being within ± 10% er early maturing bird. Another confounding of mean weight. The major problem with a factor is that as birds mature within a flock, the per- non-uniform flock is variability in age at first egg, cent production realized on a daily basis does not and so variability in feed intake. If diets are tai- reflect the number of birds laying at that time. As lored to feed intake, then late maturing smaller shown in Figure 4.2, the proportion of laying birds (with small appetites) will likely be under- birds always exceeds the percent production cal- fed. Conversely heavier, early maturing pullets culated and this difference is most pronounced in with increased appetites may be overfed at this early production. For example, at about 40% pro- time. The consequence is often a delayed peak, duction, there are, in fact, around 70% of the birds and reduced overall egg production. mature and requiring proportionally more nutri- ents than suggested by egg production alone. Fig. 4.2 Comparison of number of birds producing eggs and actual egg production SECTION 4.2 Feed and energy intake

CHAPTER 4 177 FEEDING PROGRAMS FOR LAYING HENS 4.3 Problems with heat distress becomes critical. High temperature and humid- ity combined are much more stressful to birds than T he majority of the world’s laying hens are is high temperature alone. Other environmen- kept in areas where heat stress is likely to tal factors such as air speed and air movement are be a major management factor at some also important. It is also becoming clear that adap- stage during the production cycle. The major prob- tation to heat stress can markedly influenced bird lem relates to birds not consuming enough feed response. For example, laying birds can tolerate at this time, although there are also some sub- constant environmental temperatures of 35˚C and tle changes in the bird’s metabolism that affect perform reasonably well. On the other hand, most both production and shell quality. While all types birds are stressed at 35˚C when fluctuating of poultry thrive in warm environments during day/night temperatures are involved. In the fol- the first few weeks of life, normal growth and lowing discussion, it is assumed that fluctuating development of older birds is often adversely affect- conditions exist, since these are more common ed. Obviously, the bird’s requirements for sup- and certainly more stressful to the bird. plemental heat declines with age, because insu- lating feathers quickly develop and surface Figure 4.3 shows the bird’s generalized response area, in relation to body size, is reduced. Heat to variable temperature and humidity. Regardless stress is often used to describe bird status in hot of housing system, environmental conditions of > environments, although it is obvious that more 32˚C and > 50% RH are likely to cause some degree than just environmental temperature per se is of heat distress. Table 4.12 shows typical layer involved. Because birds must use evaporative response to high environmental temperatures. cooling (as panting) in order to lose heat at high temperatures, humidity of inhaled air Table 4.12 Performance of brown egg layers at 18˚C vs. 30˚C Feed intake Egg production Egg weight Shell (% of egg) (g) 40 wk 60 wk (g/b/d) (%) 60.9 57.2 9.5 9.1 18˚C 131 91.2 9.0 8.6 30˚C 108 83.6 Adapted from Chen and Balnave (2001) SECTION 4.3 Problems with heat distress

178 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Fig. 4.3 Generalized bird response to temperature and humidity. Fig. 4.4 Environmental temperature and body heat production. The main concern under hot weather con- and is economical. However, the relationship ditions is the layer’s ability to consume feed. As between body heat production and house tem- poultry house temperature increases, then less perature is not linear, since at a certain critical heat is required to maintain body temperature temperature, the bird’s energy demands are and the birds consume less feed. In this situation, increased in order to initiate body cooling ‘environmental’ energy is replacing feed energy mechanisms. The following factors should be con- SECTION 4.3 Problems with heat distress

CHAPTER 4 179 FEEDING PROGRAMS FOR LAYING HENS sidered in attempting to accommodate the bird’s for energy. Unfortunately, the situation is not as reaction to heat stress: clear cut as depicted in Figure 4.4 and this is like- ly the reason behind the variability seen in a) Bird’s response to heat stress – flock response to various environmental conditions. Rather than lower and upper critical temperature Figure 4.4 is a schematic representation of being rigidly fixed under all conditions, heat pro- a heat stress effect. Minimal body heat production duction is likely to fluctuate in response to a num- (and hence the most efficient situation) is seen ber of very practical on-farm conditions. at around 23˚C. Below this temperature, (lower critical temperature) birds generally have to Variation in response can be caused by such generate more body heat in order to keep warm. factors as (a) increased feed intake; (b) degree of However, there is only a narrow range of tem- feathering or; (c) increased bird activity. Such perature (19-27˚C) over which heat production potential variability in bird response should be is minimal. Above 27˚C birds start to use more taken into account when interpreting the quan- energy in an attempt to stay cool. For example, titative data discussed in Figures 4.5 and 4.6. The at 27˚C, birds will start to dilate certain blood ves- whole picture is further confused by the normal sels in order to get more blood to the comb, wat- energy intake pattern of the bird (Figure 4.5). The tles, feet etc. in an attempt to increase cooling upper line of Figure 4.5 represents energy intake capacity. More easily observed is the characteristic for a 1.5 kg white egg layer. As environmental tem- panting and wing drooping that occurs at slight- perature increases, energy intake declines. However, ly higher temperatures. These activities at high above 27 – 28˚C the decline becomes quite environmental temperatures mean that the bird dramatic since the bird is changing its metabolic has an increased, rather than decreased, demand Fig. 4.5 Environmental temperature and energy balance. SECTION 4.3 Problems with heat distress

180 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS processes in response to the heat load, and young pullet, for a total need of around 115 kcal actions such as panting, etc. adversely influence ME/d for productive purposes. At moderate the feeding mechanisms in the brain and also reduce environmental temperatures, such energy yield the time available for feeding. The shaded area is readily obtained from the feed, since with aver- between the lines in Figure 4.5 represents the ener- age intakes of 270 – 275 kcal ME/bird/day, gy available for production. At around 28˚C the there is adequate energy for production and energy available for production is dramatically maintenance. However, as feed intake declines, reduced and around 33˚C actually becomes neg- available energy will decline. Although main- ative. If energy available for production is plot- tenance energy needs are less at higher tem- ted against temperature, the energy potential for peratures, the non-linear relationship (Figure egg production is clearly evident (Figure 4.6). 4.5) causes problems of energy sufficiency at around 28˚C (Figure 4.6). Above this tempera- A 60 g egg contains around 80 kcal gross ener- ture, if production and growth are to be sustained, gy, and this requires around 100 kcal ME of dietary the birds will have to use body energy reserves input, assuming 80% efficiency of utilization of in order to balance energy demands. There this ingested energy. If the bird is at 95% pro- are obvious limits to such fat reserves, especially duction, then there is a need for 95 kcal ME/d with young pullets, and so it is unlikely that the to sustain peak egg output. There will also be pullet can sustain 95% egg production for too need for 15 – 25 kcal ME for daily growth of this long a period under these conditions. Fig. 4.6 Environmental temperature and energy balance. SECTION 4.3 Problems with heat distress

CHAPTER 4 181 FEEDING PROGRAMS FOR LAYING HENS The bird has no option but to reduce egg out- developed equations that take into account put in order to sustain energy needs for main- degree of feathering, although this assumes a lin- tenance. Under actual farm conditions, the ear trend across all temperatures. Figure 4.7 uses temperatures at which critical changes occur (28˚C these equations to predict energy intake up to and 33˚C in Figure 4.6) will vary, especially around 25˚C, at which time it is assumed that a with acclimatization to temperature, but events degree of heat distress will occur and this will will likely be initiated within ± 2˚C of the val- be most prevalent for the well-feathered bird. The ues shown in Figure 4.6. response after 26˚C assumes increased energy need, as shown in Figure 4.5. The actual situ- A major factor affecting the bird’s energy intake ation may be more complex than this in tropi- in response to environmental temperature is cal regions where birds are held in open-sided feather cover, which represents insulating capac- houses and where there is the expectation of cool ity for the bird. Coon and co-workers have nightime temperatures. Fig. 4.7 ME intake of layers with 60, 75 or 90% feather cover at 10-34˚C Adapted from (Peguri and Coon, 1995) SECTION 4.3 Problems with heat distress

182 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS b) Maintaining energy balance – that energy intake will be maximized with as high a diet energy level as is possible. In order to The key to sustaining production in hot increase diet energy level, the use of supplemental climates is to maintain a positive energy balance. fat should be considered. Dietary fat has the advan- tage of increasing palatability and also reducing i) Changing diet energy level - It is well known the amount of heat increment that is produced that birds consume less feed as the energy level during its utilization for production. of the feed increases. This is because the bird attempts to maintain a given energy intake each ii) Physical stimulation of feeding activity – day. However, the mechanism is by no means Various methods can be used to stimulate feed perfect and as energy level is increased, the actual decline in feed intake is often imper- intake. Feeding more times each day usually fectly regulated, leading to ‘overconsumption’ encourages feeding activity. Feeding at cooler times of energy. As environmental temperature increas- of the day, if possible, is also a useful method of es, the mechanism seems even less perfect and increasing the bird’s nutrient intake. If artificial so increasing diet energy level is often consid- lights are used, it may be useful, under extreme ered in an attempt to stimulate energy intake. Payne environmental conditions, to consider a so-called (1967) showed this classical effect with brown midnight feeding when temperature will hopefully egg layers fed 2860 to 3450 kcal ME/kg at 18˚C be lower and birds are more inclined to eat. or 30˚C (Table 4.13). At 18˚C there is fairly When heat stress is extreme, making the diet good adjustment by the bird in that feed intake more palatable may be advantageous. Such is sequentially reduced as energy level increas- practices as pouring vegetable oil, molasses, or es and energy intake is maintained constant. At even water directly onto the feed in the troughs high temperatures, birds adjust feed intake less will encourage intake. Whenever high levels of perfectly and ‘overconsumption’ of energy fat are used in a diet, or used as a top dressing as occurs. It is not suggested that these extremes described here, care must be taken to ensure that of diet energy be used commercially, rather rancidity does not occur. This can best be achiev -ed by insisting on the incorporation of quality Table 4.13 Effect of diet energy level on metabolizable energy intake Diet energy 18˚C 30˚C (kcal ME/kg) Feed/day Energy/day Feed/day Energy/day 2860 (g) (kcal) (g) (kcal) 3060 127 363 107 306 3250 118 360 104 320 3450 112 364 102 330 106 365 101 350 Adapted from Payne (1967) SECTION 4.3 Problems with heat distress

CHAPTER 4 183 FEEDING PROGRAMS FOR LAYING HENS antioxidants in the feed and that feed not be boundary layer around the bird will be close to allowed to ‘cake’ in tanks, augers or troughs. this temperature. By increasing air speed, the Freshness of feed becomes critical under these boundary layer is disrupted, so aiding in cool- conditions. ing the bird. Table 4.15 shows the effect of air movement on the cooling effect on the bird Diet texture can also be used to advantage. and the expected increase in feed intake. Crumbles or large particle size mash feed tend to stimulate intake while a sudden change from iii) Body fat reserves – Adequacy of pullet large to small feed particles also has a transitory rearing programs become most critical when effect on stimulating intake. It is interesting to observe birds are to be subjected to hot weather in the that a sudden change from small to large crumbles time up to peak egg mass production. As seems to have a negative effect on intake (Table 4.14). detailed in Figure 4.6, the layer may well have to rely on its body energy reserves as a supple- Midnight feeding is often used when birds are ment to its diminished energy intake from the subjected to heat stress conditions. Light for 1 feed. Rearing programs designed to maximize – 2 hrs has at least a transitory effect on increas- growth have been discussed previously. The ing feed intake (1 – 3 %) and often has a long- heavier the bird at maturity, the larger the body term effect. With moderately high tempera- weight throughout lay, and hence the larger tures it may only be necessary to provide lighting, the potential energy reserve and also the while with extreme hot weather it is advisable greater the inherent feed intake (Table 4.16) to also run the feeder lines during this 1 hour time period. An interesting observation with midnight It is not suggested that extremely fat pullets are feeding is the bird’s dramatic increase in water desirable, but it is obvious that birds of opti- intake (see Figure 4.8). Layers will eat more feed mum weight with a reasonable fat reserve are in hot weather conditions, if the ‘effective tem- best suited to heat stress situations. Pullets perature’ is reduced. This is sometimes achieved that are subjected to heat stress and have less with evaporative cooling depending upon inher- ‘available’ energy than that required to sustain ent levels of humidity. A less costly, but very effec- production, have no recourse but to reduce tive system of stimulating intake, is to increase egg mass output in terms of egg weight and/or air movement. Body temperature of the bird is egg numbers, since maintenance energy close to 41˚C, and the air within the 1-2 mm needs are always a priority. Table 4.14 Effect of sudden change in feed particle size on feed intake 5-7d following this change Feed (g/bird/day) Regular Crumb size Regular to large 112b Regular to small (> 2.4 mm) (<2.4 mm) 81c 124a SECTION 4.3 Problems with heat distress

184 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS Table 4.15 Cooling effect of air movement (wind chill) and expected increase in feed intake of layers maintained at 30ºC Air movement Cooling effect Expected increase in (meters/second) (˚C) feed intake (g/b/d) 1 0.5 2 Up to 1 g 0.75 3 1–2g 1.0 4 2-3g 1.25 5 3-4g 1.50 6 4–5g 1.75 5–6g Table 4.16 Leghorn pullet size and energy intake Body Weight (g) Daily energy consumption 18-25 wks (kcal) 18 wk 24 wk 247 254 1100 1400 263 273 1200 1500 1300 1600 1400 1700 c) Protein and amino acids – therefore faced with a difficult problem of attempt- ing to maintain ‘protein’ intake in situations of It is tempting to increase the crude protein reduced feed intake, when crude protein per se level of diets during heat stress conditions. This may be detrimental. The answer to the problem has been done on the basis of reduced feed intake, is not to increase crude protein, but rather to increase and hence protein levels have been adjusted the levels of essential amino acids. By feeding syn- upwards in an attempt to maintain intakes of thetic amino acids, we can therefore maintain the around 19 g crude protein/bird/day. It is now real- intake of these essential nutrients without the ized that such adjustments may be harmful. need to catabolize excess crude protein (nitrogen). When any nutrient is metabolized in the body, General recommendations are, therefore, to the processes are not 100% efficient and so increase the use of synthetic methionine and some heat is produced. Unfortunately, protein lysine and perhaps threonine to maintain daily is the most inefficiently utilized nutrient in this intakes of approximately 420, 820 and 660 mg regard and so, proportionately more heat is respectively for birds around peak egg production. evolved during its metabolism compared to that of fat and carbohydrates. The last thing that d) Minerals and vitamins – a heat stressed bird needs is additional waste heat being generated in the body. This extra heat pro- Calcium level should be adjusted according duction may well overload heat dissipation to the anticipated reduction in feed intake, so that mechanisms (panting, blood circulation). We are birds consume at least 4.2 g per day. Under extreme conditions, this may be difficult since, SECTION 4.3 Problems with heat distress

CHAPTER 4 185 FEEDING PROGRAMS FOR LAYING HENS as previously indicated, high energy diets are also cial effects of increasing the potassium levels in desirable and these are difficult to achieve with the diet, although again, this must be accomplished the increased use of limestone or oyster shell. Table only after careful calculation, since higher lev- 4.17 shows the diet specifications needed to main- els can be detrimental to electrolyte balance. While tain intakes of Ca, P, and vitamin D3, all of few reports indicate any improvement in adding which are critical for eggshell quality. supplemental B vitamins during heat stress, there are variable reports of the beneficial effects Table 4.17 Diet nutrient levels with the fat soluble vitamins. Although not needed to maintain constant intake always conclusive, increasing the levels of vita- of these nutrients at varying levels mins A, D3 and E have all been shown to be advan- of feed intake tageous under certain conditions. While vitamin C (ascorbic acid) is not usually considered in poul- Feed intake Av P Ca Vit. D3 try diets, there is evidence to support its use (g/d) (%) (%) (IU/kg) during hot weather conditions. Under most cir- 80 0.52 5.3 4125 cumstances, birds are able to synthesize their needs 90 0.47 4.7 3660 of vitamin C but under heat stress, such production 100 0.42 4.2 3300 may be inadequate and/or impaired. Adding up 110 0.38 3.8 3000 to 250 mg vitamin C/kg diet has proven benefi- cial for layers in terms of maintaining production Because it is also necessary to increase the when temperatures exceed 28ºC. energy level of the diet when feed intake is low, then it is counterproductive to add high lev- e) Electrolyte balance – els of limestone and phosphates, which effectively dilute the feed of all nutrients other than Ca and As environmental temperature increases, phosphorus. The problem of potential calcium birds increase their respiration rate in an attempt deficiency is most often met by top dressing feed to increase evaporative cooling. As birds pant, with oystershell or large particle limestone. The they tend to lose proportionally more CO2 and deficit of vitamin D3 is best met with use of D3 so changes in acid-base balance can quickly devel- supplements in the drinking water rather than for- op. With mild to severe alkalosis, blood pH may mulation of a new premix. change from 7.2 through 7.5 to 7.7 in extreme situations. This change in blood pH, together with There seems to be some benefit to adding sodi- loss of bicarbonate ions can influence eggshell um bicarbonate to the diet or drinking water. quality and general bird health and metabolism. However, this must be done with care so as not Under such heat stress conditions, it is the avail- to impose too high a load of sodium on the bird, ability of bicarbonate per se which seems to be and so salt levels may have to be altered. This the major factor influencing eggshell synthesis should be done with great caution, taking into and in turn, this is governed by acid-base bal- account sodium intake from the drinking water, ance, kidney function and respiration rate. which can be quite high during heat stress con- ditions. In most situations, there will be no Shell formation normally induces a renal negative effects from replacing 30% of supple- acidosis related to the resorption of filtered mental salt with sodium bicarbonate on a kg for bicarbonate. At the same time, shell secretion kg basis. There is also an indication of benefi- induces a metabolic acidosis because the formation SECTION 4.3 Problems with heat distress

186 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS tohfeinlsiboleurbalteioCnaoCfOH3-firoonms.HSCuOch3 and Ca2+ involves Acclimatization to heat stress is a con- H- release would founding factor because short-term (1-2 d) acute conditions are more problematic to the bird. For induce very acidic and physiologically destructive example, pullets grown to 31 weeks under con- stant 35 vs 21ºC conditions exhibit little differ- conditions, and be necessarily balanced by the bicar- ence in pattern of electrolytes. If birds are allowed to acclimatize to high environmental tem- bonate buffer system in the fluid of the uterus. While peratures there is little correlation between plas- ma electrolytes and shell quality. Temporary acute a mild metabolic acidosis is therefore normal heat stress and cyclic temperature conditions are undoubtedly the most stressful to the bird. during shell synthesis, a more severe situation Severe electrolyte imbalance can be prevented leads to reduced shell production because of by considering the ratio of cation:anion in diet formulations. However, it must be accepted that intense competition for HCO3 as a buffer rather the diet is only one factor influencing potential than for shell formation. A severe metabolic aci- imbalance, and so, general bird management and welfare also become of prime importance. dosis can be induced by feeding products such as Electrolyte balance is usually a consideration of Na+K-Cl in the diet, and under most dietary sit- NH4Cl, and this results in reduced shell strength. uations, this seems a reasonable simplification. In this scenario, it is likely that NH4 rather than Cl- Electrolyte balance is usually expressed in terms of mEq of the various electrolytes, and for an indi- is problematic because formation of urea in the liver vidual electrolyte this is calculated as Mwt ÷ 1,000. This unit is used on the basis that most miner- (from NH4) needs to be buffered with HCO3 als are present at a relatively low level in feeds. ions, creating added competition for shell formation. As an example calculation, the mEq for a diet con- taining 0.17% Na, 0.80% K and 0.22% Cl can Conversely, feeding sodium bicarbonate, especially be calculated as follows: when Cl- levels are minimized, may well improve shell thickness. Under commercial conditions, the need to produce base excess in order to buffer any diet electrolytes must be avoided. Likewise it is important that birds not be subjected to severe res- piratory excess, as occurs at high temperatures, because this lowers blood bicarbonate levels and in extreme cases, causes a metabolic acidosis. Under practical conditions, replacement of part (30- 35%) of the supplemental dietary NaCl with NaHCO3 may be beneficial for shell production. Sodium Mwt = 23.0, Eq = 23g/kg, mEq = 23mg/kg Diet contains 0.17% Na = 1,700 mg/kg = 1700/23 mEq = 73.9 mEq Potassium Mwt = 39.1, Eq = 39.1g/kg, mEq = 39.1mg/kg Diet contains 0.80% K = 8,000 mg/kg = 8,000 /39.1 mEq = 204.6 mEq Chloride Mwt = 35.5, Eq = 35.5g/kg, mEq = 35.5mg/kg Diet contains 0.22% Cl = 2,200 mg/kg, = 2,200/35.5 mEq = 62.0 mEq overall diet balance becomes Na + K – Cl = 73.9 + 204.6 – 62.0 = 216.5 mEq. SECTION 4.3 Problems with heat distress

CHAPTER 4 187 FEEDING PROGRAMS FOR LAYING HENS Table 4.18 Electrolyte content of feed ingredients INGREDIENT Na K Cl Na+K-Cl (mEq) Corn 0.05 0.38 0.04 108 Wheat 0.09 0.52 0.08 150 Milo 0.04 0.34 0.08 82 Soybean meal 0.05 2.61 0.05 675 Canola meal 0.09 1.47 0.05 400 Meat meal 0.55 1.23 0.90 300 Fish meal 0.47 0.72 0.55 230 Cottonseed meal 0.05 1.20 0.03 320 A balance of around 250 mEq/kg is usual, and and 10% fish meal, the balance is only 75 so for this diet, there needs to be either an mEq/kg. The milo-fish diet would need to be sup- increase in Na or K level of the diet, or a plemented with NaHCO3. decrease in Cl level. Assuming that heat stress cannot be tempered Under practical conditions, electrolyte bal- by normal management techniques, then elec- ance seems to be more problematic when chlo- trolyte manipulation of the diet may be benefi- ride levels are high. On the other hand, use of cial. However, the technique should be differ- NaHCO3 to replace NaCl, as is sometimes rec- ent for immature birds compared to egg layers. ommended during heat stress, can lead to a With layers, there is a need to maintain the deficiency of chloride. Changes in diet electrolyte bicarbonate buffer system as it influences eggshell balance most commonly occur when there is a quality. As such, diet or water treatment with sodi- major change in ingredient usage and espe- um bicarbonate may be beneficial, again empha- cially when animal protein sources replace soy- sizing the necessity to meet minimum chloride bean meal and vice versa. Table 4.18 outlines requirements. On the other hand, treatment of electrolyte balance of some major feed ingredients. respiratory alkalosis in layers with acidifiers such as NH4Cl, while relieving respiratory dis- Within the cereals, Na+K-Cl for milo is low, tress, may well result in reduced shell quality. For while wheat is high relative to corn. Major dif- immature pullets, treatment with electrolytes ferences occur in the protein-rich ingredients, and is often beneficial and there is less need for relative to soy, all sources are low in electrolyte caution related to bicarbonate buffering. Up to balance. As shown in Table 4.18, this situation 0.3% dietary NH4Cl may improve the growth rate develops due to the very high potassium content of heat stressed birds, although it is not clear if of soybean meal. Careful consideration to elec- any effect is via electrolyte balance/blood pH or trolyte balance must therefore be given when simply via the indirect effect of stimulating changes are made in protein sources used in for- water intake. Under commercial conditions, mulation. For example, the overall balance for adding salt to the drinking water of young birds a diet containing 60% milo and 25% soy is has been reported to alleviate bird distress and 210 mEq/kg, while for a diet containing 75% milo to stimulate growth. SECTION 4.3 Problems with heat distress

188 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS f) Water – only limited success, possibly related to change in ‘taste’ of the water and/or the nutrients stim- A nutritional factor often overlooked during ulating bacterial growth in the water lines. heat stress is the metabolism of water. It is well However there are always positive results seen known that birds in hot environments drink when the drinking water is cooled. Feed intake more water, yet this has not been capitalized upon can be stimulated as much as 10% by cooling to any degree. Table 4.19 shows the water bal- the water 5 to 8˚C when environmental tem- ance of layers held at 22˚C or 35˚C. perature is around 30 – 32˚C. Although this man- agement practice is relatively easy to achieve under Table 4.19 Water balance of layers experimental conditions, it is a much more at 22ºC or 35ºC (ml/bird/day) complex engineering problem with large com- mercial flocks. Water intake 22˚C 35˚C Manure water 210 350 g) Effect of physical diet change – Egg water 85 150 Respiration water 50 50 Discussion to date has centered on the 75 150 potential of diet manipulation to alleviate heat stress. However, diet change per se may be detri- Layers will drink at least 50% more water at mental under certain conditions. It seems that 35 vs. 22˚C. If such adaptation is not seen, then when the bird is confronted with an acute heat it likely relates to birds not being able to consume stress situation, diet change may impose anoth- sufficient quantities of water at times of peak need. er stress, which merely accentuates any meta- Figure 4.8 shows the daily pattern of water bolic imbalance. For example, it was recently intake of layers when lights are on from 6:30 a.m. reported that a diet change brought about by to 6:30 p.m. There is a doubling of water intake adding fat caused an immediate rise in body tem- in the last 3 hours of the day, compared to all pre- perature for up to 4 d which can be disastrous vious times, and so the water system must be able to the bird and cause death. At the same time, to accommodate this demand, especially in the diet change had the desirable effect of stim- hot weather conditions. ulating energy intake. For this reason, it is sug- gested that under extreme heat stress condi- Since water intake is often increased at tions of 36 – 40˚C, that no diet change be times when feed intake is decreased, it would be implemented, since it could lead to death from logical to try and provide limiting nutrients in the heat prostration. water. However, this concept has met with Fig. 4.8 Daily pattern of relative water intake. Lights on @ 6:30am for 12 hrs/d SECTION 4.3 Problems with heat distress

CHAPTER 4 189 FEEDING PROGRAMS FOR LAYING HENS Table 4.20 Effect of diet change on layer performance during heat stress @ 21 wks of age @ 33 wks of age Diet type Egg Feed Shell Egg Feed Shell prod. intake deformation prod. intake deformation Control (%) (%) (g) (µm) Control (g) (µm) High CP Pre-test High Energy 82 86 21 92 101 24 7 d (18ºC) High Density 92 64a 22b 71 50a 35b Stress Control 90 36c 24a 56 20b 41ab 3 d (35ºC) High CP 94 40c 23ab 60 27b 46a High Energy 96 53b 24a 67 28b 37b Post- High Density 84a 76a 26c 77a 84a 30b stress 4 d 39c 24b 35ab 45b 61bc 41a (18ºC) 56b 33b 41a 64a 57c 42a 69ab 76a 31bc 67a 73ab 29b a-c means followed by different letters are significantly different Under these conditions, it would be useful that sudden diet change merely imposed an to be able to prejudge the rise in environmen- additional stress and was not beneficial to the bird. tal temperature and make the diet change ear- lier, when the bird is under ‘moderately’ stress- h) Summary of nutritional ful conditions (28 – 35˚C). However, even with management during heat short-term heat stress situations, it may be inad- visable to change the diet (Table 4.20). 1. Never place underweight pullets in the laying house. They will always remain small with low feed In these studies, birds were fed a control ration intake and have little body fat reserve to sustain for 7 d at an environmental temperature of energy balance through the period of peak egg 18˚C. A heat stress of 35˚C was suddenly mass production. imposed, and birds offered the same control diet, or diets high in energy, protein or all nutrients 2. Increase the energy level of the diet with a min- (termed high density). Feed intake was depressed imum of 2850 kcal ME/kg, ideally by incorporation almost immediately in response to heat stress, of fats or oils. Limit the level of crude fiber. although changes in egg production and shell qual- ity were not seen until after the 3 d stress peri- 3. Reduce crude protein (17% CP maximum) while od. However, during this post-stress period, birds maintaining daily intakes of methionine (420 showed a dramatic loss in egg numbers and shell mg), lysine (820 mg) and threonine (660 mg). quality. There was no instance of diet change alle- viating the effects of heat stress, and in most sit- 4. Increase mineral-vitamin premix in accordance with uations, production deteriorated. Under such con- anticipated change in feed intake. Maintain ditions of short-term heat stress, it is suggested daily intakes of calcium (4.2 g) and available phos- phorus (400 mg). SECTION 4.3 Problems with heat distress

190 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS 5. Where shell quality is a problem, consider 8. Keep drinking water as cool as possible. the incorporation of sodium bicarbonate. At this time, monitor total sodium intake, and 9. Use crumbled feed or large particle mash feed ensure adequate chloride levels in the diet. if available. 6. Use supplemental vitamin C at 250 mg /kg. 10. Do not make any diet change when sudden short-term (3 – 5 d) heat stress occurs. 7. Increase the number of feedings per day and try to feed at cooler times of the day. 4.4 Phase Feeding es. For this reason, it should be economical to reduce the nutrient concentration of the diet. At P hase feeding refers essentially to reduc- this time, it is pertinent to consider a conventional tions in the protein and amino acid level egg production curve of a layer, and superimpose of the diet as the bird progresses through both egg weight and daily egg mass output a laying cycle. The concept of phase feeding is (Figure 4.9). based on the fact that as birds get older, their feed intake increases, while egg mass output decreas- Fig. 4.9 Bird age: egg production, egg weight and egg mass. SECTION 4.4 Phase Feeding

CHAPTER 4 191 FEEDING PROGRAMS FOR LAYING HENS If nutrient density is to be reduced, this should average feed intake of 95 g/day, this would be not occur immediately after peak egg numbers, equivalent to diets containing 20, 19 and 16% but rather after peak egg mass has been achieved. protein. It must be stressed that these values should The two reasons for reducing the level of dietary be used only as a guide, and after all other fac- protein and amino acids during the latter stages tors have been properly considered. If a reduc- of egg production are first, to reduce feed costs tion in the level of protein is made and egg and second, to reduce egg size. The advantages production drops, then the decrease in nutrient of the first point are readily apparent if protein costs intake has been too severe and it should be are high, but the advantages of the second point immediately increased. If, on the other hand, pro- are not so easily defined and will vary depend- duction is held constant and egg size is not ing upon the egg pricing. When a producer is being reduced, then the decrease in protein or amino paid a premium for extra large and jumbo eggs, acid intake has not been severe enough and it there is no advantage to using a phase feeding pro- can be reduced still further. The amino acid to gram unless eggshell quality is a problem. be considered in this exercise is methionine, since this is the amino acid that has the greatest effect It is difficult to give specific recommendations on egg size. As for the situation with protein, too regarding any decrease in dietary protein or large a single step reduction in methionine will amino acid level that can be made to temper egg likely lead to loss in egg production and possi- size without also decreasing the level of production. bly an increase in feed intake. A one-time The appropriate reduction in protein level will reduction in diet methionine of 20% has been depend on the season of the year (effect of tem- reported to reduce egg size by 3% with con- perature on feed consumption, age and production commitant loss in egg production of 8%. of the bird, and energy level of the diet). Hence, it is necessary that every flock be considered on Phase feeding of phosphorus has also been rec- an individual basis before a decision is made to ommended as a method of halting the decline in reduce the level of dietary protein. As a guide, shell quality invariably seen with older birds. it is recommended that protein intake be reduced Using this technique, available phosphorus lev- from 19 to 18 g/day after the birds have dropped els may be reduced from approximately 0.42 – to 90% production, and to 15-16 g/day after they 0.46% at peak production to slightly less than 0.3% have dropped to 80% production. With an at end of lay. Table 4.21 shows an example of Table 4.21 Phase feeding of major nutrients after peak egg mass, assuming constant daily feed intake at 100 g Bird characteristics Diet levels (%) Methionine Calcium Age (wks) Egg production Crude Av. protein 0.41 4.2 phosphorus (%) 0.38 4.3 19.0 0.36 4.4 0.44 <35 93 0.34 4.5 18.0 0.41 45 90 17.0 0.36 55 85 16.0 0.32 70 80 SECTION 4.4 Phase Feeding

192 CHAPTER 4 FEEDING PROGRAMS FOR LAYING HENS phase feeding of protein, methionine and phos- concept of 100% production, regardless of age, phorus, related to controlling egg size, opti- is misleading. mizing shell quality and minimizing feed costs. Advocates of phase feeding indicate that A major criticism of phase feeding is that birds birds can be successfully managed by reducing do not actually lay ‘percentages’ of an egg. For protein/amino acid contents of the diet – others example, if a flock of birds is producing at 85% suggest that nutrient specifications are too high production does this mean that 100% of the flock to start with initially, and that phase feeding is laying at 85% or is 85% of the flock laying at merely accomplishes normalization of diet in rela- 100% production. If a bird lays an egg on a spe- tion to requirement. The bottom line is that envi- cific day, it can be argued that its production is ronmental and management conditions vary 100% for that day, and so its nutrient requirements from flock to flock, and certainly from season to are the same regardless of the age of bird. season within a flock. For this reason, the basis Alternatively, it can be argued that many of the of phase feeding must be an accurate assessment nutrients in an egg, and especially the yolk, of the nutrient intake relative to requirement for accumulate over a number of days, and so this production, growth and maintenance. 4.5 Formulation changes and feed texture W ith diets formulated to least cost what negated the savings in feed costs seen ingredient input, it is often necessary with absolute least cost. The economic situation to change ingredient concentrations, in terms of egg return minus feed cost was in favor and depending upon economic circumstances, of conventional least cost, mainly due to a dou- the computer invariably ‘asks’ for major changes bling of the mortality rate with the major swings at certain times. In these situations, nutritionists in diet composition. It seems that while the are often reluctant to make major ingredient sub- absolute least cost diets are initially attractive in stitutions in consecutive diets, on the basis that reducing feed cost, they offer little overall eco- such change may adversely affect feed intake and nomic advantage and generally pose an additional hence product. In a recent study, birds were fed economic risk. a range of diets over a 12-month cycle, with the The texture of diets for laying hens is perhaps situation of least cost where major changes in ingre- subject to more variability than for any other class dient use occurred in most months. Control birds of poultry. In some countries, very fine mash- were fed least cost formulated diets, although in es are used, whereas crumbles are used in other this situation major ingredient changes from areas. There is little doubt that any type of feed month to month were not allowed, rather these texture can be made to work physically, although changes occurred more gradually as occurs bird response is not always the same. Our commercially. Birds responded reasonably to these research data suggests that regardless of nutrient changes and no major adverse effects were profile, layers prefer large particles of feed. seen. However, a slight improvement in egg pro- When layers were offered a crumbled diet, they duction and egg size with a conventional least show a marked preference for the largest size par- cost system, where diet changes were tempered ticles available. Smaller particles of feed only to prevent drastic swings in diet composition, some- SECTION 4.5 Formulation changes and feed textures

CHAPTER 4 193 FEEDING PROGRAMS FOR LAYING HENS start to disappear later within a 24 h period, when In this study, feed samples were taken direct- all the large particles have been eaten. In this ly from the feed tank and then at points pro- study, there was no disappearance of very fine gressively further from the initial point of distribution particles <0.6 mm, although this result may be within the feed trough. Particle and nutrient sep- confounded with the break down of large parti- aration were seen at all farms (Table 4.22). cles. Feed intake increased when birds were sud- With crumbled feed, particle size was dramat- denly presented with feed of small particle size, ically reduced as feed traveled along the trough, and intake temporarily declined when birds although this was not associated with any major were offered only large size particles. A criticism change in nutrient profile. Higher calcium lev- of mash diets is that they tend to separate out when els per se in the trough, rather than the tank, relates used in long runs of feed trough, and especial- to feed samples in the trough including all feed ly where continous chain feeders are used. From in front of the bird that included fine particles a survey of commercial flocks in Ontario, we found beneath the feeder chain. Particle separation was comparable physical separation of feed with also seen with the mash feeds, although this was both mash and crumbles (Table 4.22). only during the first 18 m run of the feed trough. Table 4.22 Particle segregation and calcium analysis of feed collected from farms using either mash or crumbles (%) Type of feed Particle At feed Distance along feed trough (m) Crumbles size (mm) tank +18 +36 +72 +108 Mash >2.36 46.0 29.8 25.3 20.6 16.0 >1.18 28.8 26.5 25.5 24.7 23.7 >0.85 6.9 9.4 10.1 10.9 11.1 >0.71 3.4 5.5 6.1 6.7 7.1 >0.60 3.2 5.6 6.2 6.7 7.1 <0.60 11.7 23.2 26.8 30.3 33.8 %Calcium 4.5 >2.36 3.5 4.3 4.5 4.7 10.5 >1.18 17.3 10.0 8.3 8.5 21.0 >0.85 22.7 21.1 20.0 19.6 15.1 >0.71 11.9 13.4 13.2 14.5 9.0 >0.60 7.2 8.9 9.0 9.2 8.2 <0.60 7.4 8.6 9.0 9.3 36.2 %Calcium 33.5 38.0 40.5 38.9 5.0 5.3 5.6 4.0 4.9 4.6 Nutrition and shell quality duces a fairly consistent quantity of shell mate- rial for each egg, regardless of its size. As the egg N utrition can have a major impact on gets larger, therefore, the shell necessarily gets eggshell quality, and is often the first thinner, and this becomes more prone to breakage. parameter considered when problems arise. After peak egg production, the layer pro- SECTION 4.6 Nutrition and shell quality