title: Posthatch incubation time and early growth of broiler chickens.
abstract: Fertile eggs from broiler breeder hens were hatched to evaluate the effects of time of hatch and time held in the incubator posthatch on subsequent chick weights to 4 weeks of age. All chicks suitable for removal at 486, 492, 498, 504, 510, 516, and 522 hr of incubation in Trial 1 were weighed at their respective hatch times. One-half of each group remained in the incubator until 522 hr and the rest were placed in brooding pens at the initial weighing time, with water provided immediately and feed 6 hr later. The earlier the chicks hatched, the greater was the weight loss when held in the incubator to 522 hr (over 10% loss for those hatched at 486 and 492 hr). Males removed at hatch times of 486, 492, 498, and 504 hr were significantly heavier to 4 weeks of age than were their hatch mates held to 522 hr. A similar but less pronounced response was noted for females. Time on feed did not account for the total differences noted. Earlier hatching female chicks in Trial 1 were heavier at the time of hatch. They tended to maintain this weight advantage to 4 weeks of age when not held, but lost it when left in the incubator for the total hatching period. This effect was less pronounced for males. Trial 2 eggs were obtained from a different breeding source that had a larger egg size. Resulting chick weights were a higher percentage of initial egg weight than those in Trial 1. With hatch times of 492, 500, 508, and 516 hr, the trend was similar to that in Trial 1 but much less pronounced.
mesh_terms: D000818:Animals; D001835:Body Weight; D002642:Chick Embryo / Q000254:growth & development; D002645:Chickens / Q000254:growth & development*; D005260:Female; D007185:Incubators / Q000662:veterinary*; D008297:Male; D013997:Time Factors