Effects of Photoperiods during the Laying Period on Broiler Breeder Performance.

The effects of increasing the laying period day-length from 13 to 16 hours were examined in Ross (308) broiler breeders. The birds reared on 8-h photoperiods and then were photo-stimulated at 21 weeks by increasing the photoperiods from 8 h of light, 16 h of darkness (8L:16D) to 11L:13D. Then the birds were given an additional 60 min of light per week cumulatively, such that in different experimental groups the 12L:12D, 13L:11D, 14L:10D, 15L:9D and 16L:8D photoperiods were achieved in 22, 23, 24, 25 and 26 weeks of age, respectively. The photoperiods remained unchanged until the experiment was finished at 50 weeks of age. The 16L:8D group had a poorer feed conversion and less egg production and egg mass than the other 3 groups (P<0.05). The total settable egg percentage was significantly lower for 15L:9D and 16L:8D than for 13L:11D and 14L:10D birds (P<0.05). The 13L:11D and 14L:10D h hens had more double-yolked and broken or abnormal eggs, followed by the 15L:9D h birds, and the 16L h birds (P<0.05). The mean egg weight of 14L:10D birds was significantly more than for 16-L h birds (P<0.05), with 13L:11D and 14L:10D birds were intermediated (P<0.05). The percentage of hatchability was higher in 13L:11D h hens followed by the 15L:9D and the 16L:8D birds (P<0.05), with 14L:10D h hens intermediated between 13L:11D and 15L:9D groups. The findings of this study suggest that 13L:11D was the optimal photoperiods for Ross 308 broiler breeders in the laying period up to 50 weeks of age. [ABSTRACT FROM AUTHOR]