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Nutrition and Broiler Breeder Performance: A Review with Emphasis on Response to Diet Protein
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NUTRITION AND BROILER BREEDER PERFORMANCE: A REVIEWWTH EMPHASIS ON RESPONSE TO DIETPROTEIN GREGORIO LOPEZ and STEVE LEESON' Department ofAnimal and Poultry Science, University of Guelph, Guelph, ON N l G 2W1, Canada Phone: (519) 8244120, Eit. 3681 F M : (519) 836-9873
INTRODUCTION Although the importance of protein in poultry diets is well known, the literature contains very few comprehensive studies on the effect of dietary protein and amino acids on broiler breeder performance. Studies report on a wide range of independent variables, such as body size, feed consumption, egg production, hatchability, and offspring performance - although there are a few integrating studies. The literature shows that these factors all play an important role in the choice of dietary protein concentrations. 1
To whom correspondence should be addressed
EGGPRODUCTION Many studies have centered on the protein needs of broiler breeders (BB) during the critical period of onset of egg production [l,2, 3, 4, 5, 6, 71. Other workers [8, 9, 101 have studied the effect of feed and nutrient intake on egg production during the entire laying period. So far, there is little information available on the needs of BB hens for energy and protein at different phases of the laying period. Variability in results has been attributed to differences in body size [l, ??], level of feed intake
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Primary Audience: Nutritionists, Breeders
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to dissociate the effect of any additional protein from the effect of the limiting amino acids, especially methionine, lysine, and tryptophan [22].Often dietary crude protein intake has been confoundedwith intake of limiting amino acids in studies involving egg production. While some researches reported good production by BB with intakes of 27.7 g crude protein and 1272 mg of lysine/bird/day [13], others report daily needs as low as 18.6 g crude protein and 1022 mg of lysine [21]. Bowmaker and Gous [13] studied the effect of dietary levels of lysine and methionine on BB performance; they reported poor performance with low levels of these amino acids. Higher levels (918-1272 mg lysine and 335-524 mg methioninefbirdlday) resulted in the best performance, especially in terms of egg production, suggesting that the lysine needs could have initially been underestimated. A lysine requirement of 765 mg/bird/day is reported by the National Research Council [26].Higher levels of lysine to support good performance have also been reported by other authors [19,20,21, 22,251. Studies on sulphur amino acid (SAA) requirements of BB for egg production show some variability.While Waldroupetal. [19] reported the SAA requirement to be 666 mg/bird/day for egg production, Cave et al., [27] reported higher values (960-1050 mg). To date there are no reports on the ratio of essential to nonessential amino acids appropriate for egg production in BB.
EGGWEIGHT AND EGG COMPOSITION EGG WEIGHT A number of factors affect size of egg of BB hens, including genetics [ll],chronological age [ul,25,281, photoperiod [29,30], and sexual maturity [8,31,32]. Other studies have also identified body weight [9] and diet [l,8, 10, 20, 25, 30, 331 as factors influencing egg weight. The most important dietary factors known to alter egg weight are dietary fat (linoleic acid), protein, and certain amino acids. Dietary fat has been reported to increase egg weight of Leghorn hens [34,35,36,37,38, 391. This effect can be primarily attributed to However, the the intake of linoleic acid [a]. role of dietary fat on egg weight remains un-
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[8, 9, 103, and season of the year [12]. Other reasons for such variable results are, egg mass output [13] and the use of data extrapolated from leghorn type hens [13, 141. Energy plays an important role in BB performance with both maintenance and egg production. This concept cannot be ignored in studies aimed at quantitating protein and amino acid needs. Most energy serves to meet the maintenance requirement, so only about one third of energy intake is used for egg production [15]. Such requirements are not constant, but are affected by environmentaltemperature, eggoutput, growth, age, and degree of energy restriction [16,17]. Early studies reported a severe decline in egg production of BB hens following energy restriction to 368 kcal and 21 g CP/bird/day 20% less than that consumed by control birds [8]. Energy intake above 370 kcal/bird/daywas reported to be adequate for both maintenance and egg production [16]. Spratt et al. [18] reported 330 kcal ME as the energy requirement for maintenance and production of BB in cages. This estimate, is however, generally lower than that based solely on egg production, which has been reported to be around 400 kcal/bird/day [13,14,19,20,21,22,23]. For BB hens subjected to feed restriction, energy and amino acid intake can be predicted relative to the feeding schedule. This restriction of nutrients is important because of the fact that BB hens are reported to consume as much as 643 kcal ME/bird/day when fed ad libihrm [lo]. Whereas early experiments invariably involved restriction of feedper se [8, %], in recent experiments considerable effort has been taken to maintain constant protein intake such that only energy intake is restricted. Pearson and Herron [20] found that maximum egg production of BB in floor pens occurred at intakes of 413 kcal ME and 19.5 g of protein/bud/day. Spratt and Leeson [25] reported that 385 kcal ME and 19 g CP are required by individual caged BB hens for maximum egg production. Waldroup et al. [19] suggested that protein requirements of BB hens fed on corn-soybean diets supplying an energy intake of 425 kcal ME/biud/day was 20-22 @day. The quality of dietary protein is determined by its amino acid content and the balance of it relative to overall requirement. There is limited published information on specific amino acids required by BB. It is difficult
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daily egg output to be 793 mg of lysine and 321 mg of methionine. Harms and Ivey [23] suggested the daily lysine requirements for egg production, egg weight, and egg output to be 824, 806, and 819 mg, respectively, when protein intake was greater than 18.6 glday. Cave et al. (271 varied the daily protein intake of BB from 21.6 g to 24.8 glday, supplemented with SAA from 816 to 1056 mg. Egg production, egg weight, and egg output were higher for hens consuming 24.8 @day although increasing S A A supplementation up to 960 mg at 21.6 g protein intake resulted in increased egg mass, egg production, and egg weight. Bowmaker and Gous [13] showed that small incrementsin intake of amino acids (lysine and methionine) that were close to the optimum resulted in equal proportional response in rate of lay and egg weight, but that when there were severe deficiencies of lysine and methionine, egg production was reduced to a greater extent than was egg weight. This effect has also been observed in commercial layers [45]. It seems that when the protein and amino acid intakes are low, birds tend to adjust first their egg production and secondly their egg weight. This information suggests that to establish optimum protein and amino acid intakes for BB hens, we must predict changes in egg output rather than isolated responses to egg production and egg weight. EGG COMPOSITION Knowledge of the chemical composition and physiological processes for yolk and albumen formation has mostly been obtained from work with commercial layers. This information has been useful for interpretation of factors influencing egg composition of BB hens. The ratio of yolk to albumen in an egg is useful in the interpretation of changes that can occur in egg composition. Some results indicate that egg weight, shell weight, and percent yolk increase, while albumen and shell percentages of total egg weight decrease as a result of increasing bird age [46,47,48].Increase in yolk weight is usually correlated with increase in The effect of bird age on egg egg weight [a]. composition has been described by Williams and Sharp [49], who investigated the ovarian development and morphology in both BB hens and commercial layers. They reported that smaller and more numerous yellow-yolky ovarian follicles are observed in 26-wk-old
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clear. Some trials indicate only transitory improvement in egg weight [37,39, 411 while other studies report no effect of supplemental fats [42, 431. Scragg et al. [40] reported that brown-egg layer hens responded with increasing egg weight to linoleic acid intake up to 2.7 g/bird/day. This fmding is 1.6 g higher than NRC [26] recommendations for Leghorn hens. This maximum response to linoleic acid intake has not been well established for BB hens, although Brake et al. [30] found that supplementation of 24 g of linoleic acidkg diet fed to BB from 22 to 64 wk of age had some effect on egg weight. Much of the controversy surrounding the relationship between egg weight and diet fat is due to the confounding effect of the energy contribution of fat. Balnave [38] investigated the isoenergetic replacement of dietary oil (linoleic acid) by starch, which resulted in a reduction in egg weight, suggesting that the effect of increasing egg weight was due to some componentsin the oilper se rather than in their energy content. Many experiments carried out to evaluate energy intake have associated an increase in egg weight with moderate [20, 25, 331 and high energy intake [lo, 441. In some of these experiments little information on linoleic acid intake is provided, and often birds were fullfed [lo, 441, indicating that not only energy but quite possibly linoleic intake was excessive. The effects of dietary protein and amino acids on egg weight have been thoroughly investigated in BB [1,ul, 25,331. However, again there is considerable variability in reported data, which is partly explained by the fact that requirements for egg production and egg weight are sometimes difficult to separate. Therefore, any effects of protein on egg weight must be considered in relation to normal egg production. Wddroup et al. [19] suggested the protein requirement for both egg production and egg weight to be comparable for BB hens, while other workers [2!5J report protein requirements of 19 &id /day to achieve optimum egg production and 25 &ird/day to achieve maximum egg weight. These latter observations are in agreement with the findings of other workers [lo, 33,441. An alternative approach is to define the optimum level of dietary protein and amino acid intake needed to maximiie egg output [13,14]. Bowmaker and Gous [13] suggest the requirements for a 3 kg BB producing 45 g
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FERTILITY AND HATCHABILITY Fertility and hatchability are major factors to be considered in performance of BB hens. Fertility and hatchability can be influenced by different factors; therefore, it is important to differentiate the extent to which changes in overall hatchability are due to changes in fertility. Fertility of BB hens is affected primarily by male performance [56, 57, 58, 59, 60,611. Factors such as shell quality have also been related to low fertility [9, 621. However, the effect of high energy intake and its consequence on body weight has been described as the main cause of low fertility associated with BB hens [6,9,10,45,63]. Pearson and Herron [20] observed a highly significant decrease in fertility associated with an energy intake of 450 kcaUbirdlday in the last trimester of the laying circle. At that time hens and cockerels were significantly heavier than birds fed 363 kcal/bid/day. From this data it is difficult to differentiate the effect of high energy from that of associated weight increase because both affect fertility. In this experiment protein intake was not thought to be a factor in low fertility. Whon et al. [64] found that if such heavy body weight is obtained before 30 wk of age, then fertility is affected throughout the entire laying period. In contrast, Bilgili and
Renden [65] did not fmd this relationship between heavy body weight and low fertility. Thisinformation implies that body weight control, rather than energy intake per se, is the major factor affecting fertility. The relationship between fertility and hatchability has also been examined [6,10,65]. Reports indicate that hatchability is often normal in situationsof low fertility.In many experiments low "hatchability,"in the sense of eggs which hatch into viable embryos, is most often due to low fertility. Changes in hatchability of fertile eggs in BB hens have been reported to be related to many factors, such as storage time [66,67], incubation position [ a ] , incubation conditions [67,69], and shell quality [9,44, 62,70,71]. Other researchers have found that the age of the bird [67,72] and egg size [73] also influence hatchability. Only a few reports describe the effect of diet energy and protein on true hatchability. Pearson and Herron [74] reported low hatchability between 26 and 36 wk in birds fed high protein (27 g/bird/day) and low energy (363 kcal ME/bird/day), manifested as an increase in the percentage of dead embryos in the second week of incubation and an increase in the number of pipped eggs at the end of incubation. They suggested that embryo mortality at this age is likely to be caused by nutritional deficiencyin the egg and that hatchability could be depressed when daily allowances of protein and energy exceeded 15 g:239 kcamid.
OFFSPRING PERFORMANCE The biological function of the BB egg is to produce a viable embryo with the features required to produce a broiler chicken. A fertile egg will provide a closed environment within which all nutritional needs of the embryo have to be met, with the notable exception of gaseous exchange. Therefore, the physiological condition of the BB hen and the egg are related to normal embryo development. A high positive relationship between egg weight and chick size has been reported by several workers [28,73,75,76,77,78,79], and chick weight is usually 62-7696 of egg weight [73,79,80,81, 82,831. Most of the variation in chick weight at hatch is accounted for by differences in the fresh weight of the egg, weight loss during incubation, and the weight of the shell and
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hens than in 82-wk-old hens. As laying hens become older, the initial decrease in egg production and increase in egg weight is due to a reduction in the rate of recruitment of yellowyolky follicles, which grow to a larger size before ovulation [49]. Chemical composition of eggs can be influenced by dietary protein level [&, 50, 51, 521. Butts and Cunningham [51], for example, reported that a reduction in albumen is observed when birds receive low-protein diets, suggesting that these diets are lower in essential amino acids (EM).This diet leads to insufficientprotein synthesis to meet the needs for egg formation. Other workers (53, 54,551 report little or no variation in egg protein content and egg composition in response to changes in dietary protein or amino acid levels. Currently, there is insufficient information to conclude how changes in dietary protein and amino acids will affect egg composition of BB eggs-
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associated the effect of the maternal diet composition with offspring performance [20, 64, 93, 94, 951. Aitken et al. [94] reported that broilers from parents fed a high nutrient density diet (energy and protein) were significantly heavier at hatch and at 63 days in comparison with chicks from breeders fed low energy diets. Wilson and Harms [63] found that protein intake of 19.9 to 23 glbirdlday had no effect on 49 day body weight of offspring; similar results were observed by both Spratt and Leeson [95] and Pearson andHerron [20]. They also reported lack of effect of energy intake from 325 to 450 kcal/bird/day on broiler weight at 41 and 48 days. A better understanding of the effect of maternal diet on broiler performance depends on controlling the confounding influence of egg weight and age of the flock.
BODY WEIGHT AND BODY WEIGHT CONTROL Broiler breeder hens have the potential for becoming overweight and obese [64, 961. This situation is associated with low egg production [3,9,10,44],low fertility[9,10,44], and poor shell quality [lo, 441.The term "obesity" as related to breeders has not been well quantified, and no such production criteria have been established in either immature or mature birds. A number of studies refer to BB hens that attained heavy body weight due to full feeding programs as obese or heavy birds [10, 12,441.This terminology seems to put emphasis on body weight in defining obesity rather than on the physiological effect of an excessive fat deposition condition, which may relate more closely to energy intake. Many experiments have tried to determine effective nutritional methods for controlling body weight at different phases of the bird's life so as to give improved adult performance. Control over immature body weight seems critical for life-cycle performance of the BB. Several methods have been investigated so far, including restriction of energy by feeding high-fiber diets [19,97],lowprotein diets [97,98], and lower levels of E M such as lysine [97, 99, 100, 1011. Alternative methods involve some form of feed restriction (skip-aday and daily feeding) which, so far, have been used successfully in controlling body weight [8,32,65,98, 100,101, 102,1031.Early studies
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other residues at hatch [69]. Egg size increases with breeder age [B], so it would be expected that bird age will also affect chick weight. However, this effect was not observed by Shanawany [B], who investigated the effect of egg size and age of flock. He found that flock age had no effect on hatching weight. In this experiment the weight of embryos to 18 days was greater for older birds, and these embryos hatched earlier. The author attributed these effects to increased shell porosity, more efficient utilization of nutrients by embryos from older birds, and more efficient deposition of nutrients for embryonic development in the eggs from older birds. Some studies have shown that chick weight at hatch affects subsequent broiler growth [73,75,76,84,85,86], while others have shown any residual effect of chick weight to quickly disappear [77,79,80,87l. It has been reported that a 1 g difference in egg weight results in some 10-12 g difference in body weight at 8 to 9 wk [76,88]. Examination of the effect of egg size on chicken mortality has not shown consistent results. Whereas some workers reported no signifcant effect [73,85l, high mortality has been reported in chicks coming from small eggs [84, 86, 89, 901. Such high mortality has also been related to maternal age, where higher mortality is seen in chicks from young breeders [90]. McNaughton et al. [90]suggested that this viability could be explained by the fact that older breeders produce chicks with significantly more body fat at hatching. While better feed efficiency of broiler chicks has been related to larger egg size [84, 911, results are not always convincing [73, 75, 85,861. Obviously, effect egg size has on feed efficiency may be confounded with age of the breeder flock. Pone et al. [92]reported that maternal age had a significant effect on live body weight of broilers, reporting less feed consumption with broilers from younger parents. This effect was also observed by Pinchasov [79], who reported heavier body weight of birds from older breeders due to higher feed intake. Because chick size is positively correlated with egg size, it seems reasonable to assume that changes in the diet which influence eggweightwill also influence the size of the chick at hatch. However, whether or not breeder nutrition modifies subsequent broiler performance is still not clear. Few studies have
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It seems that a minimum age and minimum body weight must be attained before the onset of egg production. Other studies suggest 2.3 to 2.7 kg as the minimum body weight for onset of commercial egg production [104]. This body weight must comprise a minimum lean body mass [105, 1061 as well as a certain amount of fat stores which seem essential for yolk formation and ovulation [105,107]. After maturity, BB’s tend to eat more and rapidly gain weight to develop all their reproductive organs, displaying a remarkable compensatory growth. This effect is reported to be related to the degree of feed restriction previously applied and to the amount of feed provided in the time prior to reaching peak egg production [6, 241. A body weight gain of 1.1kg from 21 to 36 wk of age has been associated with optimum performance [20]. Lack of maturity and excessive feed allowance at this time raises the possibility of developing birds heavy with excessive body fat [96]. Many studies have shown that after the peak of egg production, nutrient requirements for egg formation decline and the potential for overconsuming energy and thus fat deposition increases [l,8,10, 12,24,33]. For mature birds, body weight gain has been related to excessive intake of energy rather than to protein intake [l, 10,331.However, protein intake per se has also been reported to have an effect on body weight. While Spratt and Leeson [25] reported a minimal effect of dietary protein intake on body weight, Harms and Ivey [23] reported a more substantial effect. Studies in chickens have found that increasing dietary protein resulted in lower lipogenesis [108,109]. This effect has also been ascribed to the addition of limiting amino acids such as lysine.
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4. Cave, N.AG., 1984. Effect of a high-proteindiet fed prior to the onset of la on rformance of broilerbreeder pullets. Poultry Sci. 6$18g1827.
2. Bomsteln, S. and Y.Lev, 1982. The energy requirements of broiler breeders durin the pullet-layer transition wriod. Poultw Sci. 61:755-!65.
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3. McDaniel, G.R, 1983. Factors affecting broiler breederperformance.5. EYfectsof preproduction feeding regimens on reproductive performance. Poultry Sci. 62:1949-1953.
6. Ingram, D.R and H.R Wilson, 1 9 8 7 . 8 9 feedin of broiler breeders nor to peak egg production. Nutr. keports Intl. 36:839&.
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of different methods of controlling body weight in BB were carried out with the aim of delaying sexual maturity of birds raised in natural conditions. This approach appeared to be necessary for pullets, especially during the cooler part of the year when day-length is increasing. During this time birds tended to eat more and gain more weight, leading to premature sexual maturity and early onset of egg production [loll. These effects are associated with laying of eggs that are unsuitable for incubation. Studies have also indicated a positive correlation between degree of feed restriction and delay in sexual maturity [24, 32, 97, loo]. While feed restriction delays maturity, it is not clear if the delay in onset of egg production is due solely to low body weight or to other factors associated with feed restriction. Bennett and Leeson [%] found that birds which were raised under controlled conditions, were light-stimulated at 20 wk of age, and were fed high (H) and low (L) levels of energy did not show a si&icant differencein day of first egg: 180 (H) to 184 (L). Their results, however, show a significant difference in body weight and in body fat: 3130 g (H) to 2679 g (L) and 624 g (H) to 395 g (L)respectively. They suggested that if the birds had been light stimulated before 20 wk of age, those on the high energy diets might have been able to begin egg production sooner than did the birds fed the lower energy diets. These suggestions are in agreement with the finding of Leeson and Summers [31], who reported that by modifying the feed allowance of BB pullets to achieve a target body weight of 2.1 kg of body weight at different ages and immediatelyimposing light stimulation, early onset of egg production was achieved without change in body composition. However, these early maturing birds were not able to sustain their egg production.
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55. Naber, EC., 1979. The effect of nutrition on the composition of the egg. Poultry Sci. 58518-528. 56. Wilson, H.R, N.P. Pksco, ER Miller, and W.G. Nesbeth, 1979. Prediction of the fertility tential of broiler breeder males. World’s Poultry Sci. &:95-118. 57. WUson., J.L. G.R McDanieL and C.D. Sutton. 1987. Dieta protein levels for broiler breeder males: Poultry Sci. %:237-242. I
58. Harris, G.C., J.A Benson, and RS. Sellers, 1984. The influence of day-length, body weight, and age on the reproductive ability of broiler breeder cockerels. Poul try Sci. 63170S1710. 59. Hocking, P.M., 1989. Effect of dietary crude protein concentration on semen yield and quality in male broiler breeder fowls. Br. Poultry Sci. 30:935-945. 60. Ansa4 G.A, RB. Buckland, D.C. Crober, AE Sefbn, and B.W. Kennedy, 1 9 n . Fertility of broiler males in relation to bodyweight, strain of female and age. Poultry Sci. 56:1694 (Abstr). 61. Hocking, P.M. and S.R Duff, 1989. Musculo-skeleta1 lesions in adult male broiler breeder fowls and their relationship with body wei t and fertility at 60 weeks of age. Br. Poultry Sci. 3 0 d & 4 .
63. Wilson, H.R and RH. Harms, 1984. Evaluation of s ecifications for broiler breeders. Poultry Sci. 631&0-1406. 64. Wilson. H.R. D.R Ineram. and RH. Harms. 1983. Restricted feeding of broTler breeders. Poultry Sci: 62:113>1141. 65. Bugill, S.F. and J.A. Renden, 1985. Relationship of body fat to fertility in broiler breeder hens. Poultry Sci. 64:1394-1396. 66.Malher, C.M. and K.F. Laughlin, 1979. Storage of hatching eggs: The interaction between parental age and early embryonic development. Br. Poultry Sci. 20:595604. 67. Kirk, S., G.C. Emmans, R McDonald, and D. Amof 1980. Factors affecting the hatchability of eggs from broiler breeders. Br. Poultry Sci. 21:37-53.
68. Bnuer, F., S.G. Tullett, and H.R. Wilson, 1990. Effects of setting eggs small end up on hatchability and pthatching performance of broilers. Br. Poultry Sci. 31:715-724. 69. Tulletf S.G. and F.G. Burton, 1982.Factors affecting the weigt and Y t e r status of the chick at hatch. Br. Poultry ci. 23361 369. 70. Peebles, E D . and J. Brake, 1985. Relationship of eggshell porosity to stage of embryonic development in broiler breeders. Poultry Sci. 64:238&2391. 71. Bennett, C.D., 1992. The influence of shell thickness on hatchability in commercial broiler breeder flocks. J. Appl. Poultry Res. 1:61-65. 72. Harris, G.C., 1984.Phriologyand management of aging turkey and broiler breeders. Pages 219-225 in: Re roductive Biology of Poult F.J. Cunningham, P.Jf Lake, and D. Hewitt, eds.%r. Poultry Sci. Ltd., Edinburgh, UK. 73. Morris, RH., D.F. Hessels, and R.J. Bishop, 1968. The relationship between hatching egg weight and subsequent rformance of broiler chickens. Br. PoultIy Sci. 9:305-E5. 74. Pearson, R.A. and K.M.Herron, 1982b. Effects of maternal energy and protein intakes on the incidence of malformations and time of death during incubation. Br. Poultry Sci. 23:7i-n. 75. Wiley, W.H, 1950. The influence of egg weight on the pre-hatching and post-hatching growth rate in the fowl. 11. Egg weightchick weight ratios. Poultry Sci. 29595604. 76. Goodwin, K., 1961. Effect of hatching egg size and chicksize upon subsequent growth rate in chickens. Poultry Sci. 40:1408 (Abstr). 77. Washburn, K.W. and RA. Guill, 1974. Relationship of embryo weight as a percent of egg weight to efficiency of feed utilization in the hatched chick. Poultry Sci. 53:766-769. 78. Shanawany, M.M., 1987. Hatching weight in relation to e wei t in domestic birds. World’s Poultry Sci. J. 43:fi7-11!? . 79. Pinchasov, Y., 1991. Relation between the weight of hatching e and subsequent early erformance of broiler chicks%. Poultry S i . 32109-113. 80. Godfrey, G.F., C. Williams, and C.E Marshall, 1953. The relative influence of egg size, age at sexual
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45. Morris, T.R and RM. Gous, 1988.Partitioning of the res nse to protein between egg number and egg weight.%r. Poultry Sci. 29:93-99. 46.Anderson, IC, IC Flwingtr,and I. Palmlenyi, 1978. Restricted feeding and different protein levels to two strains of S C W L hybrids. 2. Effects on egg composition. Swedish J. Agr. Res. 8241-247. 47. Fletcher, D.L, W.M. Britlon, AP. Rahn, and S.I. Savage, 1981. The influence of layer flock age on e components yieldsand solids content. Poultry Sci. 60:98g 987. 48. Fletcher, D.L, W.M. Brillon, G.M. Pes14 AP. Rebn, and S.I. Savage, 1983. The relationship of layer flock age and e weight on e com nent yields and solids content. #&try Sei. 6 Z l k 1 8 g ; )
62. McDaniel, G.R, D.A Roland, and M A Coleman, 1979. The effect of e shell uality on hatchability and embryonic mortality.youltry %i. 58:lO-13.
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89. McClung, M.R and RM. Smith, 1949. Relationt and growth rate of market chick-
90.McNnugbbn, J.L, J.W. Dealon, and F.N. Reece, 1978. Effect of age of parents and hatching eggweight on broiler chick mortality. Poultry Sci. 5738-44. 91. Proudfoot, F.G., H.W. Hulan, and K.B. McRae, 1982. Effect of hatching egg size from semi-dwarf and normal maternal meat parent genotypes on the performance of beoiler chicksn. Poultry SCi. 61:655-660. 92. Pone, D.K., LD. Andrms, and L Stamps, 1985. The effect of maternal age on broiler performance on litter and a raised perforated floor. Poultry Sci. 64500602. 93. Penquite, R. and T.T. Milby, 1941. Hatching weight of chicks from hens fed different protein levels. Poultry Sci. u):195-200.
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Aitken, J.R, ES. Merritt, and RJ. Curlis, 1969. The influence of maternal diet on egg size and progeny performance in meat-type hens. Poultry Sci. 48:596401. 95. Spratt, RS. and S Lctson, 1990. Influence of intake on develo ment of broiler breeder pullets. Anim. Sci. 70:259266. %. Bennett, C.D. and S. Lceson, 1990. Influence of intake on develo ment of broiler breeder pullets. Anim. Sci. 70259266.
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98. Harms, RH., B.L Damron, and H.R Wilson, 1968. Performance of broiler breeder pullets as influ-
enced b composition of grower and layer diets. Br. Poultry sei. L59-366. 99. Singsen, EP., J. Nagel, S.G. Patrick, and LD. Matterson, 1965. The effect of a lysine deficiency on m w t h characteristics. aee at sexual maturitv. and reurou ductive performance of"meat-type pullets.'Poultry*Sci. 44A467-1473. 100. Lee,PJ.W., k L Gulliver, andT.R Morris, 1971. Restricted feeding of broiler breeder pullets during the nod and itseffect on productivity and breeding. Br. Pou try Sci.' 12499-510. . 101. Luther, LW., W.W. Abbott, and J.R Couch, 1976. Low lysine, low protein, and skip-a-day restriction of summer and winter reared broiler breeder pullets. Poultry Sci. 55:2240-2247. 102. Watson, AN., 1975. Reproductive activity of broiler hens sub'ected to restricted feeding during rearing. Br. Poultry !ki. 16259-262. 103. Bennett, C.D. and S. Leeson, 1989. Growth of broiler breeder pullets with skip-a-day Venus daily feeding. Poultry Sci. 6883'5438.
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104. Brody, T., Y. Eilan, m. Soller, I. Nir, and Z Nitsan, 1980. Compensatory growth and sexual matu-
rity in broiler females reared under severe food restriction from day of hatching. Br. Poultry Sci. 21:43746. 105. Bornstein, S., I. Plavnilq andY. Lev, 1984. Body weight and/orfatness as potential determinants of the onset of e production in broiler breeder hens. Br. Poultry S i . 25323-311. 106. Soller, M., Y. Eitan, and T. Brody, 1984. The effect of diet and early quantitative feed restriction on the minimum weight requirement for onset ofsexual maturity in White Rock broiler breeders. Poultry Sci. 6312551261. 107. Pearce, J., 1971. An investigation of lipogenic and glycolytic enzyme activity inthe liver of sexually immature and mature domestic fowl. Biochem. J. 123:717-719. 108. Yeh Y.Y. and G. Leveille. 1969. Effect of dietam p t e i n on hepatic lipogenesis in the growing chick. j. utr. 98:35&366. 109. Rosebrough, RW., J. McMurtry, and N. Sleele, 1987. Energy and protein relations in the broiler. 5. Lipogenesis, g l u m e production and metabolic hormone levels as functions of age and dietaryprotein levels. Growth 5 1:309-320.
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81. O'Nell, J.B, 1955. Percentage size of chick at hatching and its relationship to growth and mortality. Poultry Sci. W761-764. 82. Whiling, ST.and G.M. Pest4 1983. Effects of the dwafinggene (dw)on eggweight, chickweight, and chick weight:e wei t ratio in a commercial broiler strain. Poultry 62g97-2302. 83. Wilson, H.R. 1991. Interrelationship of e size chick size, posthatching growth and hatchability. 'SbgOrld'J Poultry Sci. J. 47520. 84. O'NeU, J.B., 1950. Relationship of chick size to egg size and its effect upon growth and mortality. Poultry Sci. 29374 (Abstr). 85. Proudfoot, F.G. and H.W. Hulan, 1981.The influence of hatching egg size on the subsequent rformance of broiler chickens. Poultry Sci. 60:2167-21g 86. Wyatt, C.L, W.D. Weaver, and W.L Benne, 1985. Influence of egg size, eggshell quali and psothatch holdin time on broiler performance. oultry Sci. 64:204920%. 87. Kosin, I.L, H. Abplanalp, J. Gutierrez, and J.S. Carver, 1952. The influence of e size on subsequent earlygrowth of the chick. Poultry 31247-254. 88. AI-Murmd, W.K., 1978. Maternal effects on emt-embryonic growth inpoultry Br. PoultIy bryonic and Sci. 192T-ij;?;i
97. Waldroup, P.W., B.L Damron, and RH. Harms, 1966. The effect of low protein and high fiber grower diets on the performanceof broilerpullets. PoultrySci.45:393402.
NUTRITION AND BROILER BREEDER PERFORMANCE: A REVIEWWTH EMPHASIS ON RESPONSE TO DIETPROTEIN GREGORIO LOPEZ and STEVE LEESON' Department ofAnimal and Poultry Science, University of Guelph, Guelph, ON N l G 2W1, Canada Phone: (519) 8244120, Eit. 3681 F M : (519) 836-9873
INTRODUCTION Although the importance of protein in poultry diets is well known, the literature contains very few comprehensive studies on the effect of dietary protein and amino acids on broiler breeder performance. Studies report on a wide range of independent variables, such as body size, feed consumption, egg production, hatchability, and offspring performance - although there are a few integrating studies. The literature shows that these factors all play an important role in the choice of dietary protein concentrations. 1
To whom correspondence should be addressed
EGGPRODUCTION Many studies have centered on the protein needs of broiler breeders (BB) during the critical period of onset of egg production [l,2, 3, 4, 5, 6, 71. Other workers [8, 9, 101 have studied the effect of feed and nutrient intake on egg production during the entire laying period. So far, there is little information available on the needs of BB hens for energy and protein at different phases of the laying period. Variability in results has been attributed to differences in body size [l, ??], level of feed intake
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Primary Audience: Nutritionists, Breeders
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to dissociate the effect of any additional protein from the effect of the limiting amino acids, especially methionine, lysine, and tryptophan [22].Often dietary crude protein intake has been confoundedwith intake of limiting amino acids in studies involving egg production. While some researches reported good production by BB with intakes of 27.7 g crude protein and 1272 mg of lysine/bird/day [13], others report daily needs as low as 18.6 g crude protein and 1022 mg of lysine [21]. Bowmaker and Gous [13] studied the effect of dietary levels of lysine and methionine on BB performance; they reported poor performance with low levels of these amino acids. Higher levels (918-1272 mg lysine and 335-524 mg methioninefbirdlday) resulted in the best performance, especially in terms of egg production, suggesting that the lysine needs could have initially been underestimated. A lysine requirement of 765 mg/bird/day is reported by the National Research Council [26].Higher levels of lysine to support good performance have also been reported by other authors [19,20,21, 22,251. Studies on sulphur amino acid (SAA) requirements of BB for egg production show some variability.While Waldroupetal. [19] reported the SAA requirement to be 666 mg/bird/day for egg production, Cave et al., [27] reported higher values (960-1050 mg). To date there are no reports on the ratio of essential to nonessential amino acids appropriate for egg production in BB.
EGGWEIGHT AND EGG COMPOSITION EGG WEIGHT A number of factors affect size of egg of BB hens, including genetics [ll],chronological age [ul,25,281, photoperiod [29,30], and sexual maturity [8,31,32]. Other studies have also identified body weight [9] and diet [l,8, 10, 20, 25, 30, 331 as factors influencing egg weight. The most important dietary factors known to alter egg weight are dietary fat (linoleic acid), protein, and certain amino acids. Dietary fat has been reported to increase egg weight of Leghorn hens [34,35,36,37,38, 391. This effect can be primarily attributed to However, the the intake of linoleic acid [a]. role of dietary fat on egg weight remains un-
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[8, 9, 103, and season of the year [12]. Other reasons for such variable results are, egg mass output [13] and the use of data extrapolated from leghorn type hens [13, 141. Energy plays an important role in BB performance with both maintenance and egg production. This concept cannot be ignored in studies aimed at quantitating protein and amino acid needs. Most energy serves to meet the maintenance requirement, so only about one third of energy intake is used for egg production [15]. Such requirements are not constant, but are affected by environmentaltemperature, eggoutput, growth, age, and degree of energy restriction [16,17]. Early studies reported a severe decline in egg production of BB hens following energy restriction to 368 kcal and 21 g CP/bird/day 20% less than that consumed by control birds [8]. Energy intake above 370 kcal/bird/daywas reported to be adequate for both maintenance and egg production [16]. Spratt et al. [18] reported 330 kcal ME as the energy requirement for maintenance and production of BB in cages. This estimate, is however, generally lower than that based solely on egg production, which has been reported to be around 400 kcal/bird/day [13,14,19,20,21,22,23]. For BB hens subjected to feed restriction, energy and amino acid intake can be predicted relative to the feeding schedule. This restriction of nutrients is important because of the fact that BB hens are reported to consume as much as 643 kcal ME/bird/day when fed ad libihrm [lo]. Whereas early experiments invariably involved restriction of feedper se [8, %], in recent experiments considerable effort has been taken to maintain constant protein intake such that only energy intake is restricted. Pearson and Herron [20] found that maximum egg production of BB in floor pens occurred at intakes of 413 kcal ME and 19.5 g of protein/bud/day. Spratt and Leeson [25] reported that 385 kcal ME and 19 g CP are required by individual caged BB hens for maximum egg production. Waldroup et al. [19] suggested that protein requirements of BB hens fed on corn-soybean diets supplying an energy intake of 425 kcal ME/biud/day was 20-22 @day. The quality of dietary protein is determined by its amino acid content and the balance of it relative to overall requirement. There is limited published information on specific amino acids required by BB. It is difficult
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daily egg output to be 793 mg of lysine and 321 mg of methionine. Harms and Ivey [23] suggested the daily lysine requirements for egg production, egg weight, and egg output to be 824, 806, and 819 mg, respectively, when protein intake was greater than 18.6 glday. Cave et al. (271 varied the daily protein intake of BB from 21.6 g to 24.8 glday, supplemented with SAA from 816 to 1056 mg. Egg production, egg weight, and egg output were higher for hens consuming 24.8 @day although increasing S A A supplementation up to 960 mg at 21.6 g protein intake resulted in increased egg mass, egg production, and egg weight. Bowmaker and Gous [13] showed that small incrementsin intake of amino acids (lysine and methionine) that were close to the optimum resulted in equal proportional response in rate of lay and egg weight, but that when there were severe deficiencies of lysine and methionine, egg production was reduced to a greater extent than was egg weight. This effect has also been observed in commercial layers [45]. It seems that when the protein and amino acid intakes are low, birds tend to adjust first their egg production and secondly their egg weight. This information suggests that to establish optimum protein and amino acid intakes for BB hens, we must predict changes in egg output rather than isolated responses to egg production and egg weight. EGG COMPOSITION Knowledge of the chemical composition and physiological processes for yolk and albumen formation has mostly been obtained from work with commercial layers. This information has been useful for interpretation of factors influencing egg composition of BB hens. The ratio of yolk to albumen in an egg is useful in the interpretation of changes that can occur in egg composition. Some results indicate that egg weight, shell weight, and percent yolk increase, while albumen and shell percentages of total egg weight decrease as a result of increasing bird age [46,47,48].Increase in yolk weight is usually correlated with increase in The effect of bird age on egg egg weight [a]. composition has been described by Williams and Sharp [49], who investigated the ovarian development and morphology in both BB hens and commercial layers. They reported that smaller and more numerous yellow-yolky ovarian follicles are observed in 26-wk-old
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clear. Some trials indicate only transitory improvement in egg weight [37,39, 411 while other studies report no effect of supplemental fats [42, 431. Scragg et al. [40] reported that brown-egg layer hens responded with increasing egg weight to linoleic acid intake up to 2.7 g/bird/day. This fmding is 1.6 g higher than NRC [26] recommendations for Leghorn hens. This maximum response to linoleic acid intake has not been well established for BB hens, although Brake et al. [30] found that supplementation of 24 g of linoleic acidkg diet fed to BB from 22 to 64 wk of age had some effect on egg weight. Much of the controversy surrounding the relationship between egg weight and diet fat is due to the confounding effect of the energy contribution of fat. Balnave [38] investigated the isoenergetic replacement of dietary oil (linoleic acid) by starch, which resulted in a reduction in egg weight, suggesting that the effect of increasing egg weight was due to some componentsin the oilper se rather than in their energy content. Many experiments carried out to evaluate energy intake have associated an increase in egg weight with moderate [20, 25, 331 and high energy intake [lo, 441. In some of these experiments little information on linoleic acid intake is provided, and often birds were fullfed [lo, 441, indicating that not only energy but quite possibly linoleic intake was excessive. The effects of dietary protein and amino acids on egg weight have been thoroughly investigated in BB [1,ul, 25,331. However, again there is considerable variability in reported data, which is partly explained by the fact that requirements for egg production and egg weight are sometimes difficult to separate. Therefore, any effects of protein on egg weight must be considered in relation to normal egg production. Wddroup et al. [19] suggested the protein requirement for both egg production and egg weight to be comparable for BB hens, while other workers [2!5J report protein requirements of 19 &id /day to achieve optimum egg production and 25 &ird/day to achieve maximum egg weight. These latter observations are in agreement with the findings of other workers [lo, 33,441. An alternative approach is to define the optimum level of dietary protein and amino acid intake needed to maximiie egg output [13,14]. Bowmaker and Gous [13] suggest the requirements for a 3 kg BB producing 45 g
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FERTILITY AND HATCHABILITY Fertility and hatchability are major factors to be considered in performance of BB hens. Fertility and hatchability can be influenced by different factors; therefore, it is important to differentiate the extent to which changes in overall hatchability are due to changes in fertility. Fertility of BB hens is affected primarily by male performance [56, 57, 58, 59, 60,611. Factors such as shell quality have also been related to low fertility [9, 621. However, the effect of high energy intake and its consequence on body weight has been described as the main cause of low fertility associated with BB hens [6,9,10,45,63]. Pearson and Herron [20] observed a highly significant decrease in fertility associated with an energy intake of 450 kcaUbirdlday in the last trimester of the laying circle. At that time hens and cockerels were significantly heavier than birds fed 363 kcal/bid/day. From this data it is difficult to differentiate the effect of high energy from that of associated weight increase because both affect fertility. In this experiment protein intake was not thought to be a factor in low fertility. Whon et al. [64] found that if such heavy body weight is obtained before 30 wk of age, then fertility is affected throughout the entire laying period. In contrast, Bilgili and
Renden [65] did not fmd this relationship between heavy body weight and low fertility. Thisinformation implies that body weight control, rather than energy intake per se, is the major factor affecting fertility. The relationship between fertility and hatchability has also been examined [6,10,65]. Reports indicate that hatchability is often normal in situationsof low fertility.In many experiments low "hatchability,"in the sense of eggs which hatch into viable embryos, is most often due to low fertility. Changes in hatchability of fertile eggs in BB hens have been reported to be related to many factors, such as storage time [66,67], incubation position [ a ] , incubation conditions [67,69], and shell quality [9,44, 62,70,71]. Other researchers have found that the age of the bird [67,72] and egg size [73] also influence hatchability. Only a few reports describe the effect of diet energy and protein on true hatchability. Pearson and Herron [74] reported low hatchability between 26 and 36 wk in birds fed high protein (27 g/bird/day) and low energy (363 kcal ME/bird/day), manifested as an increase in the percentage of dead embryos in the second week of incubation and an increase in the number of pipped eggs at the end of incubation. They suggested that embryo mortality at this age is likely to be caused by nutritional deficiencyin the egg and that hatchability could be depressed when daily allowances of protein and energy exceeded 15 g:239 kcamid.
OFFSPRING PERFORMANCE The biological function of the BB egg is to produce a viable embryo with the features required to produce a broiler chicken. A fertile egg will provide a closed environment within which all nutritional needs of the embryo have to be met, with the notable exception of gaseous exchange. Therefore, the physiological condition of the BB hen and the egg are related to normal embryo development. A high positive relationship between egg weight and chick size has been reported by several workers [28,73,75,76,77,78,79], and chick weight is usually 62-7696 of egg weight [73,79,80,81, 82,831. Most of the variation in chick weight at hatch is accounted for by differences in the fresh weight of the egg, weight loss during incubation, and the weight of the shell and
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hens than in 82-wk-old hens. As laying hens become older, the initial decrease in egg production and increase in egg weight is due to a reduction in the rate of recruitment of yellowyolky follicles, which grow to a larger size before ovulation [49]. Chemical composition of eggs can be influenced by dietary protein level [&, 50, 51, 521. Butts and Cunningham [51], for example, reported that a reduction in albumen is observed when birds receive low-protein diets, suggesting that these diets are lower in essential amino acids (EM).This diet leads to insufficientprotein synthesis to meet the needs for egg formation. Other workers (53, 54,551 report little or no variation in egg protein content and egg composition in response to changes in dietary protein or amino acid levels. Currently, there is insufficient information to conclude how changes in dietary protein and amino acids will affect egg composition of BB eggs-
Review Article LOPEZ and LEESON
associated the effect of the maternal diet composition with offspring performance [20, 64, 93, 94, 951. Aitken et al. [94] reported that broilers from parents fed a high nutrient density diet (energy and protein) were significantly heavier at hatch and at 63 days in comparison with chicks from breeders fed low energy diets. Wilson and Harms [63] found that protein intake of 19.9 to 23 glbirdlday had no effect on 49 day body weight of offspring; similar results were observed by both Spratt and Leeson [95] and Pearson andHerron [20]. They also reported lack of effect of energy intake from 325 to 450 kcal/bird/day on broiler weight at 41 and 48 days. A better understanding of the effect of maternal diet on broiler performance depends on controlling the confounding influence of egg weight and age of the flock.
BODY WEIGHT AND BODY WEIGHT CONTROL Broiler breeder hens have the potential for becoming overweight and obese [64, 961. This situation is associated with low egg production [3,9,10,44],low fertility[9,10,44], and poor shell quality [lo, 441.The term "obesity" as related to breeders has not been well quantified, and no such production criteria have been established in either immature or mature birds. A number of studies refer to BB hens that attained heavy body weight due to full feeding programs as obese or heavy birds [10, 12,441.This terminology seems to put emphasis on body weight in defining obesity rather than on the physiological effect of an excessive fat deposition condition, which may relate more closely to energy intake. Many experiments have tried to determine effective nutritional methods for controlling body weight at different phases of the bird's life so as to give improved adult performance. Control over immature body weight seems critical for life-cycle performance of the BB. Several methods have been investigated so far, including restriction of energy by feeding high-fiber diets [19,97],lowprotein diets [97,98], and lower levels of E M such as lysine [97, 99, 100, 1011. Alternative methods involve some form of feed restriction (skip-aday and daily feeding) which, so far, have been used successfully in controlling body weight [8,32,65,98, 100,101, 102,1031.Early studies
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other residues at hatch [69]. Egg size increases with breeder age [B], so it would be expected that bird age will also affect chick weight. However, this effect was not observed by Shanawany [B], who investigated the effect of egg size and age of flock. He found that flock age had no effect on hatching weight. In this experiment the weight of embryos to 18 days was greater for older birds, and these embryos hatched earlier. The author attributed these effects to increased shell porosity, more efficient utilization of nutrients by embryos from older birds, and more efficient deposition of nutrients for embryonic development in the eggs from older birds. Some studies have shown that chick weight at hatch affects subsequent broiler growth [73,75,76,84,85,86], while others have shown any residual effect of chick weight to quickly disappear [77,79,80,87l. It has been reported that a 1 g difference in egg weight results in some 10-12 g difference in body weight at 8 to 9 wk [76,88]. Examination of the effect of egg size on chicken mortality has not shown consistent results. Whereas some workers reported no signifcant effect [73,85l, high mortality has been reported in chicks coming from small eggs [84, 86, 89, 901. Such high mortality has also been related to maternal age, where higher mortality is seen in chicks from young breeders [90]. McNaughton et al. [90]suggested that this viability could be explained by the fact that older breeders produce chicks with significantly more body fat at hatching. While better feed efficiency of broiler chicks has been related to larger egg size [84, 911, results are not always convincing [73, 75, 85,861. Obviously, effect egg size has on feed efficiency may be confounded with age of the breeder flock. Pone et al. [92]reported that maternal age had a significant effect on live body weight of broilers, reporting less feed consumption with broilers from younger parents. This effect was also observed by Pinchasov [79], who reported heavier body weight of birds from older breeders due to higher feed intake. Because chick size is positively correlated with egg size, it seems reasonable to assume that changes in the diet which influence eggweightwill also influence the size of the chick at hatch. However, whether or not breeder nutrition modifies subsequent broiler performance is still not clear. Few studies have
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It seems that a minimum age and minimum body weight must be attained before the onset of egg production. Other studies suggest 2.3 to 2.7 kg as the minimum body weight for onset of commercial egg production [104]. This body weight must comprise a minimum lean body mass [105, 1061 as well as a certain amount of fat stores which seem essential for yolk formation and ovulation [105,107]. After maturity, BB’s tend to eat more and rapidly gain weight to develop all their reproductive organs, displaying a remarkable compensatory growth. This effect is reported to be related to the degree of feed restriction previously applied and to the amount of feed provided in the time prior to reaching peak egg production [6, 241. A body weight gain of 1.1kg from 21 to 36 wk of age has been associated with optimum performance [20]. Lack of maturity and excessive feed allowance at this time raises the possibility of developing birds heavy with excessive body fat [96]. Many studies have shown that after the peak of egg production, nutrient requirements for egg formation decline and the potential for overconsuming energy and thus fat deposition increases [l,8,10, 12,24,33]. For mature birds, body weight gain has been related to excessive intake of energy rather than to protein intake [l, 10,331.However, protein intake per se has also been reported to have an effect on body weight. While Spratt and Leeson [25] reported a minimal effect of dietary protein intake on body weight, Harms and Ivey [23] reported a more substantial effect. Studies in chickens have found that increasing dietary protein resulted in lower lipogenesis [108,109]. This effect has also been ascribed to the addition of limiting amino acids such as lysine.
REFERENCES AND NOTES 1. Pearson, RA and KM. Herron, 1980. Feeding standards during lay and reproductive performance of broiler breeders. Br. Poultry Sci. 21:171-181.
4. Cave, N.AG., 1984. Effect of a high-proteindiet fed prior to the onset of la on rformance of broilerbreeder pullets. Poultry Sci. 6$18g1827.
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3. McDaniel, G.R, 1983. Factors affecting broiler breederperformance.5. EYfectsof preproduction feeding regimens on reproductive performance. Poultry Sci. 62:1949-1953.
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of different methods of controlling body weight in BB were carried out with the aim of delaying sexual maturity of birds raised in natural conditions. This approach appeared to be necessary for pullets, especially during the cooler part of the year when day-length is increasing. During this time birds tended to eat more and gain more weight, leading to premature sexual maturity and early onset of egg production [loll. These effects are associated with laying of eggs that are unsuitable for incubation. Studies have also indicated a positive correlation between degree of feed restriction and delay in sexual maturity [24, 32, 97, loo]. While feed restriction delays maturity, it is not clear if the delay in onset of egg production is due solely to low body weight or to other factors associated with feed restriction. Bennett and Leeson [%] found that birds which were raised under controlled conditions, were light-stimulated at 20 wk of age, and were fed high (H) and low (L) levels of energy did not show a si&icant differencein day of first egg: 180 (H) to 184 (L). Their results, however, show a significant difference in body weight and in body fat: 3130 g (H) to 2679 g (L) and 624 g (H) to 395 g (L)respectively. They suggested that if the birds had been light stimulated before 20 wk of age, those on the high energy diets might have been able to begin egg production sooner than did the birds fed the lower energy diets. These suggestions are in agreement with the finding of Leeson and Summers [31], who reported that by modifying the feed allowance of BB pullets to achieve a target body weight of 2.1 kg of body weight at different ages and immediatelyimposing light stimulation, early onset of egg production was achieved without change in body composition. However, these early maturing birds were not able to sustain their egg production.
Review Article 309
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