Performance of Broiler Breeders as Affected by Body Weight During the Breeding Season 1

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1 Performance of Broiler Breeders as Affected by Body Weight During the Breeding Season 1 H. R. WILSON and R. H. HARMS Department of Poultry Science, University of Florida, Gainesville, Florida (Received for publication July 1, 1985) ABSTRACT Two experiments were conducted to determine the effect of broiler breeder body weight on performance during the breeding season. Cobb feather-sexed broiler breeders were placed on five breeder-feeding programs. All programs furnished equivalent daily intakes of protein, calcium, phosphorus, salt and vitamins. Energy intakes were varied to produce five body weight treatment groups. Each treatment group consisted of eight pens of 13 hens and two cocks. Females in the heavier groups reached peak egg production at an earlier age than those in the lighter groups. This was followed by an earlier, more rapid decline in production and lower liability. Fertility was significantly (P<.05) lower in the ad libitum fed birds that also had the heaviest body weights. The effect of body weight treatments on hatchability was generally nonsignificant. Egg weights were heaviest for the ad libitum fed hens. Egg specific gravity decreased significantly (P=S.05) as body weights were increased. (Key words: body weight, broiler breeders, production) 1986 Poultry Science 65: INTRODUCTION The control of body weight during both growing and laying phases is a major concern in the management of broiler breeders. Breeder obesity is normally associated with poorer production, fertility, hatchability, livability, and feed efficiency (Singsen et al, 1958; Sherwood et al, 1964; Costa, 1981). The effect of obesity, however, is season-related, being much more severe in periods of high environmental temperatures, and, in some cases, beneficial in periods of low temperatures (Fuller et al., 1969, 1970; Wilson et al, 1983). Lower egg production and lower chick production have been reported in some cases (Pym and Dillon, 1974; Blair et al, 1976) when the feed intake of broiler breeders was restricted during the laying period without formulating to assure the necessary daily intake of specific nutrients. Wilson et al. (1983) reported that feed restriction resulted in higher fertility, hatchability, and egg specific gravity, but that decreased egg production occurred in cold weather, if proper adjustments in feed allowance were not made. According to McDaniel et al. (1981), restricted feeding of broiler breeders resulted in increased egg production, fertility, 1 Florida Agricultural Experiment Stations Journal Series No hatchability, and egg specific gravity but decreased egg and chick weight when compared to birds fed ad libitum. Ousterhout (1982) noted that overrestriction of feed reduced egg production, whereas overfeeding reduced fertility but increased egg and chick weight. Feed restriction, therefore, should be done carefully to assure adequate intake of critical nutrients. Because body weight gain is a key factor in establishing feed allotment (Pearson and Herron, 1980, 1981), a greater knowledge of the optimum body weight and body weight gain during the laying period is needed. The purpose of the present study was to determine the effect of body weight during the breeding season on production, fertility, hatchability, egg size, shell quality, and chick growth. MATERIALS AND METHODS Two experiments were conducted with Cobb Feather-Sex commercial broiler breeders. The chicks used in Experiment 1 were hatched on March 25, 1982 and had been utilized in an unrelated study in which they were full-fed to 8 weeks of age and placed on a skip-a-day grower program from 8 weeks through 30 weeks of age. Daily feeding was resumed at 30 weeks of age, and varied levels of energy were allotted at 32 weeks of age to induce body weight differences. All birds were under standard weight until 32 weeks of age. The chicks in Experiment 2 were hatched on March 21,

2 BROILER BREEDER BODY WEIGHT 1053 and were full-fed to 6 weeks of age, followed by a skip-a-day program from 6 through 22 weeks of age. Daily feeding was resumed at 22 weeks, and varied levels of energy were alloted at 26 weeks of age. The five treatment groups in Experiment 1 were: small, or body weight below the breeder's guide; standard, which approximated the breeder's guide; intermediate, or above the breeder's standard; heavy; and ad libitum. In Experiment 2, the birds were maintained at or above the suggested standard weight. The treatments were: standard, intermediate, heavy, extra heavy, and ad libitum. The standard used was that suggested by Cobb, Inc., who furnished the birds. The nutrient intake, other than energy, provided per bird per day was based on current recommendations (Wilson and Harms, 1984). This intake furnished 20.6 g protein, 4.07 g Ca, 683 total P, 754 sulfur amino acids, and 170 Na/bird/day (Table 1). These nutrients were furnished in a series of diets formulated according to the amount of feed allotted (e.g., 145, 150, 154 g/bird day). Therefore, all birds, regardless of the amount of feed allotted, received the same amount of these nutrients. The one exception to this was the treatment group that was allowed feed ad libitum; their consumption could not be anticipated close enough to provide the exact formulation necessary in Experiment 1. However, in Experiment 2, the estimate, and thus the control, was much more precise. Each treatment group consisted of 8 pens of 13 females and 2 males each. All male mortalities were replaced with extra males on the same treatment. All birds in two pens per treatment were weighed on the odd numbered weeks, and all birds in all pens were weighed on the even numbered weeks. Adjustments in energy allowance, and subsequently in diet formulation, were made weekly as necessary to maintain the desired body weights. Egg production was recorded daily and summarized by 28-day periods. Egg weight and specific gravity were determined once per month on all eggs laid on 1 day. Fertility and hatchability were determined once per month using all settable eggs laid during 5 days. Chicks hatched from eggs of breeders on all treatments, and produced when the breeders were 47 weeks old in Experiment 1 (145 to 214 chick/treatment) and 64 weeks in Experiment 2 (90 to 150 chicks/ treatment), were wing banded and grown intermingled to 7 weeks of age to determine if breeder treatments (body weight) affected progeny performance. Data were analyzed using the Statistical Analysis Systems (Barr et al, 1976), and analysis of variance procedures with significant differences between treatment means was determined with Waller-Duncan's K-ratio. RESULTS AND DISCUSSION Energy consumption values reflect the energy changes made to maintain body weight of each group (Table 2), except those fed ad libitum. Energy intake of the ad libitum group decreased dramatically as environmental temperatures increased in April (53 to 56 weeks). There was also a decrease for the heavy group in June and July (56 to 64 weeks) in Experiment 1. All other groups in Experiment 1 tended to have slightly lower energy consumption as hot weather began and then returned to the previous level by July. Energy levels of all restriced groups in Experiment 2 were essentially unchanged after 48 weeks (Table 2). The ad libitum group's energy intake gradually decreased after 44 weeks of age, reflecting an increase in environmental temperature and decreased egg production. Body weight of the small group in Experiment 1 was held below the breeder guide by approximately 200 to 275 g (Table 3). The group designated as standard was approximately on the guide until 50 weeks and thereafter was heavier. A steady increase in weight of the intermediate group was maintained throughout the laying year. The heavy and ad libitum Nutrient TABLE 1. Daily intake of major nutrients, excluding energy Protein Sulfur amino acids Methionine Lysine Arginine Tryptophan Calcium Phosphorus, total Sodium Vitamins 1 National Research Council NRC 1 Daily intake/ bird g g

3 WILSON AND HARMS O N H O H C S N N f n w C N 0 0 O s 0 \ O O O O O O etj"^ W 4» 4> 4> <U 4> *0 "O (S mcnffimmmforfim rt O T3 "O "^ T3 13 T3 u u t ^ t ^ O \ 0 \ O t H O O O O voo\g0000s0000>n^oc0 ^OrH\00\Oi-ii-iOOO O «^ u V rh & m 0 o a V +-> B) _x ^~, C) s 3 a 05 ro W J CQ < H i-h C <L> X w A,0 U U CJ O U O,Q _Cl r- oo\omflohnotsoo rtj3.qx).0.0.0, > rt rt cs O\tsr*-C0rnmm0r<i rt rtrtrtrtrtrtrtrtrt CO i-hrr»fs)c^th^-in^-m ^O 00 '-<<STt-ir>u->»nui i-h NOMtA^Oi-lrHi-lOOm (M v f l H H H N N m N N rt ol ut3t3t3'ot3'ot3 rtrt-oouuuuuu m 1> ^ t s C \ 0 0 H 0 0 O N row O N ' t ^ O N V O W H O V/ T3 O c c H C O O N O N O O O V O O X ^ O a HHVOHff)C00\^O»H J3 0 rt rt rt rt at rt rt rt m^- \0 0\miftrfiri\OH rj^o t^ooomirioooo^o g <

4 BROILER BREEDER BODY WEIGHT 1055 groups increased weight rapidly until 58 weeks (mid-april), then they plateaued or decreased. At 58 weeks, the ad libitum group weighed 4861 g of 143% of the suggested guide weight. In Experiment 2, body weight of the ad libitum and standard groups plateaued at 50 weeks and 54 weeks, respectively, while other groups continued a gradual increase throughout lay. The heavier groups of females reached a peak in egg production at an earlier age than smaller females in both experiments (Tables 4 and 5). Egg production of the ad libitum groups decreased rapidly after 40 weeks of age. The small group in Experiment 1 (Table 4) reached a low plateau of production at 36 weeks, which was maintained through 64 weeks of age with no discernable peak. The highest overall production was obtained from the intermediate group. The highest average production in Experiment 2 (Table 5) was obtained from the heavy group, followed by the intermediate and the extra heavy groups. A decrease in production occurred during the 41 to 44-week period, following a time of unusually low environmental temperatures. Egg production during the periods of increased environmental temperatures (May and June) after 56 weeks was lower in the extra heavy and ad libitum groups. These results agree with those of Fuller et al. (1969, 1970), McDaniel et al. (1981), and Wilson et al. (1983). Breeder livability was adversely affected by increased body weights (Table 6). Although the trend was apparent in Experiment 1, the effect was statistically significant only in Experiment Age (wk) Average 2 where the extra heavy and ad libitum fed birds had significantly (P<.05) lower livability. Fertility in both experiments was significantly (P«.05) lower in the group fed ad libitum (Table 6). The average fertility of the restricted groups ranged from 93.2 to 95.0% in Experiment 1 with no significant differences between treatments. The extra heavy group in Experiment 2 had fertility significantly (P«.05) lower than the standard and intermediate groups but higher than that of the ad libitum group. Early fertility of the ad libitum group was comparable to that of the restricted birds; however, it was reduced to 72, 66, 62, and 63% and 79, 77, 66, and 57% during the last four periods in Experiments 1 and 2, respectively (data not shown). This decrease coincided with increased breeder age and body weight, and increased environmental temperatures, all of which were probable contributing factors. The hatchability of fertile eggs did not differ significantly among groups that had their feed restricted in either experiment (Table 6). Although the ad libitum group had lower hatchability in both experiments, it differed significantly only from the extra heavy group in Experiment 2. Hatchability varied very little with breeder age or season. The heavy and ad libitum groups in Experiment 1 had significantly higher egg weights (Table 7), however, no significant differences were found in Experiment 2. Higher egg weights have usually resulted from higher energy intakes in broiler breeders (Pearson and Herron, 1982; Wilson etal, 1983). TABLE 4. Egg production of broiler breeders as affected by energy consumption and body weight, Experiment a 66.0 a 66.7 ab 59.4 b 52.2 C 43.6 b 43.3 b 46.6 b 44.5 b 4 94 cd 17.8 a 56.8 bc 57.2 ab 61.3 b 58.1 bc 57.8 a 57.6 a 52.3 bc 47.3 ab 52.9 bc 16.8 a 58.8 ab 71.2 a 71.2 a 67.4 a 62.8 a 63.0 a 61.3 a 54.8 a 58.6 a 18.6 a 52.0 bc 62.5 b 63.5 b 62.9 ab 59.7 a 60.4 a 57.0 ab 55.3 a 54.6 ab Small 20.0 a 50.0 C 49.2 C 49.2 C 50.0 C 46.3 b 49.4 b 52.8 bc 50.0 ab 46.3 d Means within a row having no common superscript are significantly different (P<.05).

5 1056 WILSON AND HARMS TABLE 5. Egg production of broiler breeders as affected by energy consumption and body weight. Experiment 2 Age Extra heavy (wk) Average 47.5 a 68.1 ab 68.2 ab 59.7 a 58.6 b 55.7 b 52.9 C 49.2 b 42.7 b 39.2 b 55.2 ab 40.4 b 73.4 a 72.3 a 65.7 a 67.3 a 64.2 a 58.2 bc 50.4 b 47.2 b 39.9 b 57.0 ab 39.6 b 68.4 ab 70.7 a 62.0 a 65. l a 60.3 ab 60.7 ab 59.4 a 55.6 a 45 oab 60.0 a 35.3 b 64.2 b 64.3 b 62.2 a 64.9 a 62.0 ab 66.4 a 60.6 a 55.3 a 51.2 a 58.6 a a-d Means within a row having no common superscript are significantly different (P<,05). Egg specific-gravity decreased significantly as body weights or energy allotments were increased (Table 7), although the average specific gravity of all groups fell within the normal range. Similar results were reported by McDaniel et al. (1981) with caged broiler breeders. Wilson et al. (1983) reported that full-fed broiler breeders on litter floors produced eggs with lower specific gravity than hens which had their feed restricted. The growth of progeny of either sex to 49 days of age was not significantly different among treatments in either experiment. These results indicate that present guides for broiler breeder body weights may be too low. Treatment 27.2 e 53.8 C 57.4 C 48.2 b 52.8 e 58.8 ab 55.5 bc 54.7 ab 55.6 a 51.7 a 52.3 b Several factors can be expected to influence the optimum body weight, including strain, season of hatch, environmental temperatures, housing (controlled environement vs. open), and genetic changes in the breeder stock. Another major potential factor is that of an interaction between the layer management program with the brooding and growing management programs. The birds in these experiments were placed on the skip-a-day grower program at 8 and 6 weeks of age in Experiments 1 and 2, respectively, which is later than recommended commercially. However, the 22-week body weights were 120 g below standard in Experiment 1 and on standard in Experiment 2. Further work is needed to TABLE 6. Livability, fertility, and hatchability of fertile eggs of broiler breeders as affected by energy consumption and body -weight 1 Livability ] Fertility,2 Hatchabii lity 2 Small Extra heavy 97.l a 92.3 a 82.7 a 88.5 a 88.5 ab 74.0 C 79.8 bc 93.2 a 94.8 a 95.0 a 77.l b - (%) 97.6 a 95.4 a 94 gab 89.9 b 79.3 C 89.3 a 88.6 a 82.7 a 84.6 a 81.2 a 87.7 ab 87 7ab 86.8 ab 88.4 a 82.6 b ' ' Means within a column having no common superscript are significantly different (P<.05). 1 Experiment 1 = to 64 weeks; Experiment 2 = to 68 weeks. 'Measured on 5 day's eggs each 4 weeks; combined average.

6 BROILER BREEDER BODY WEIGHT 1057 TABLE 7. Weight and specific gravity of eggs from broiler breeders as affected by energy consumption and body weight Egg weight 1 Specific gravity 1 Treatment Small Extra heavy 68.7 b 69.7 b 69.4 b 71.4 a 71.8 a (g) 70.8 a 70.9 a 70.8 a 70.6 a 72.1 a a b c d d a-d Means within a column having no common superscript are significantly different (P<.05). 1 Measured on 1 day's eggs each 4 weeks; combined average. determine the effect of grower programs on the ideal body weight and weight gain during the production period. REFERENCES a b b c d Barr, A. J., J. H. Goodnight, J. P. Sail, and J. T. Helwig, A User's Guide to SAS 76. SAS Inst., Raleigh, NC. Blair, R., M. M. MacCowan, and W. Bolton, Effects of food regulation during the growing and laying stages on the productivity of broiler breeders. Br. Poult. Sci. 17: Costa, M. S., Fundamental principles of broiler breeders nutrition and the design of feeding programmes. World's Poult. Sci. J. 37: Fuller, H. L., D. K. Potter, and W. Kirkland, Effect of delayed maturity and carcass fat on reproductive performance of broiler breeder pullets. Poultry Sci. 48: Fuller, H. L., D. K. Potter, and W. Kirkland, Effect of varying energy intake and daylength during the growing period on obesity, age at maturity and production of settable eggs by heavy breed chickens. 14th World's Poult. Congress 2: McDaniel, G. R., J. Brake, and R. D. Bushong, Factors affecting broiler performance. 1. Relationship of daily feed intake level to reproductive performance of pullets. Poultry Sci. 60: Ousterhout. L. E., The effects of ration complexity and feeding level on broiler breeder performance. Poultry Sci. 61: Pearson, R. A., and K. M. Herron, Feeding standards during lay and reproductive performance of broiler breeders. Br. Poult. Sci. 21: Pearson, R. A., and K. M. Herron, Effects of energy and protein allowances during lay on the reproductive performance of broiler breeder hens. Br. Poult. Sci. 22: Pearson, R. A., and K. M. Herron, Relationship between energy and protein intakes and laying characteristics in individually-caged broiler breeder hens. Br. Poult. Sci. 23: Pym, R.A.E., and J. F. Dillon, Restricted food intake and reproductive performance of broiler breeder pullets. Br. Poult. Sci. 15: Sherwood, D. H., C. D. Caskey, B. A. Krautmann, M. C. Van Wormer, S. B. Smith, and R. E. Ward, Management and feeding of meat-type breeder chickens. Poultry Sci. 43: Singsen, E. P., J. D. Matterson, J. Tlustohowicz, and L. M. Potter, The effect of controlled feeding, energy intake and type of diet on the performance of heavy-type laying hens. Poultry Sci. 37: Wilson, H. R., and R. H. Harms, Evaluation of nutrient specifications for broiler breeders. Poultry Sci. 63: Wilson, H. R., D. R. Ingram, and R. H. Harms, Restricted feeding of broiler breeders. Poultry Sci. 62:

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