The effect of ad libitum and regulated feeding on the growth, body composition and reproductive performance of broiler breeders

Two experiments were conducted to investigate the effect of two feeding systems, ad libitum (A) and regulated (R) feeding on the growth and reproductive performance of broiler breeders in floor pens and in cages from day old to 55 weeks of age. The degree of restriction used was more severe than some years ago and regulation started at an earlier age. The opening literature review deals with the management of broiler breeders, experiments to control breeding weight, the effect of nutrition on the growth, the control of feed intake in the fowl and energy requirements. In addition the factors affecting reproductive fitness of broiler breeders and responses to artificial insemination and natural mating are also reviewed. In the first experiment the objective was to compare the growth, feed intake and body composition of females and males on A and, R feeding. The starter and grower feeds contained 12.2 and 12.5 MJ ME/kg. At 10 weeks the body weight of A birds was twice that of the R birds. This difference was maintained to about 20 weeks. Regulated females did not catch up the growth of ad libitum females while regulated males reached similar body weight to ad libitum males. At 55 weeks the body weight of the A males and females was 5.29 and 4.79 kg and for the R males and females was 4.84 and 3.51 kg. To achieve target weight with both sexes the highest level of feed restriction was 65 per cent during the growing period. The highest fat content of the carcass weight in A females was 9 times that of females on R feeding and twice more protein than thos on R, by 20 weeks of age. From 30 weeks the carcass protein of females was relatively constant, whereas in the males growth of protein continued until 40 weeks, after which it was relatively constant. Second experiment was conducted to investigate the effects of dietary energy levels on feed intake, energy intake of females and to study the reproduction by artificial insemination of caged hens. Three breeder feeds (L, M and H) containing 10.1, 12.2 and 13.3 MJ ME/kg respectively, were used. Experiment 2 was conducted in two phases which were 22 to 35 weeks (phase 1) and 36 to 54 weeks (phase 2). The feeds were offered to the ad libitum fed birds and only feed M was given to those hens fed regulated amounts of feed. At 36 weeks of age, the number of treatments was increased from 4 to 10. The 6 treatments comprised ad libitum hens changed from L to H, from M to R or from H to L (treatments LH, MR and HL) and hens on R changed from R to L, from R to M or from R to H (treatments RL, RM and RH). Daily feed intake values directly decreased as dietary energy level increased. The highest daily feed intakes were 194 and 184 g/b for hens on L and M respectively at 30-31 weeks of age while for those on H it was 165-g/b at 28-29 weeks, and, for those on R it was 181 g/b at 34-35 weeks of age. Ad libitum hens adjusted their feed intake to dietary energy levels better than was expected on the basis of previous research by other workers. Throughout the first phase, the highest daily weight gain occurred with hens on R feeding while during the second phase it occurred with hens on RH. After 35 weeks of age hen-day production of hens on regulated feeding and those hens previously on R (RL, RM and RH) was about 19 per cent greater than ad libitum groups. The body fat content of hens previously on R did not affect their egg production. As with experiment 1, the egg weights of ad libitum fed birds was heavier than those produced from the regulated birds. The fertility and hatchability for all hens mated with ad libitum males in cages were higher than those on the floor except those on feed H which was lower. For hens mated with regulated males the levels of fertility and hatchability were lower than those on the floor except hens on H which had a higher hatchability. The main effect of ad libitum feeding of males was to depress the reproductive performance of all females. There was a higher mortality associated with ad libitum feeding and a high energy layers feed (H or LH groups). (Abstract shortened by ProQuest.