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 in-creasing 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 dou-ble-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.