Effects of breeder age on embryonic development, hatching results, chick quality, and growing performance of the slow-growing genotype.

The present study aimed to ascertain the effects of slow-growing breeder age on embryo development, incubation results, and chick quality and of the interaction between breeder age and hatching time on initial performance. A total of 630 hatching eggs obtained from a commercial flock of slow-growing broiler breeders (Isa Label Naked Neck) were evaluated in 2 experiments. The first experiment evaluated embryo development and hatching results for broiler breeder age treatments of 38 and 51 wk, whereas the second experiment evaluated broiler chick performance. For the second experiment, chicks were distributed in a 2 x 2 factorial randomized block (sex) experimental design consisting of 2 breeder ages (31 or 58 wk) and 2 hatching times (479-485 and 491-497 h). At 18 d of embryonic development, embryos of 51-wk-old breeders were larger than those of 38-wk-old breeders (P < 0.05), whereas yolk-free chick weight was similar (P > 0.05). Embryo organ weight was similar for the 2 breeder ages (P > 0.05); however, there was greater development of intestinal villi for embryos of the 51-wk-old breeders. There were no differences between breeder ages in hatchability and chick quality score (P > 0.05). Yolk-free chick weight at pulling was greater (P < 0.05) for chicks from 51-wk-old breeders. Hatching time did not affect performance from 1 to 7 d (P > 0.05); however, chicks hatching at 491-497 h had better performance from 1 to 28 d than did chicks hatching at 479-485 h (P < 0.05). In conclusion, the age of slow-growing breeders affects embryo villi development and chick weight but does not improve incubation results or chick quality. Chicks hatching later (491-497 h) had better performance results than chicks hatching earlier (479-485 h).