Effect of age at photostimulation on reproductive performance of Beijing-You Chicken breeders.

This work studied the effect of age at photostimulation on reproductive performance of Beijing-You Chicken (BYC) breeders. A total of 384 fourteen-week-old BYC breeder hens were randomly allocated to 4 treatments of 96 birds each, with 2 replicates per treatment. The treatments represent photostimulation at 16, 18, 20, and 22 wk of age, respectively (PS16, PS18, PS20, and PS22) by incrementally increasing day length from 8L:16D to 14L:10D and by increasing lighting intensity from 10 to 80 lx. Egg production was recorded for each replicate until 51 wk. Four birds randomly selected from each treatment were sacrificed to characterize sexual organ development at 4 time points: 1 D before photostimulation and 2, 4, and 6 wk after photostimulation. Eggshell quality at peak laying was measured. The results showed that the changes in ovary and oviduct weight in PS22 were 8.68- and 4.27-fold higher than in PS16 at 6 wk after photostimulation. PS16 had an earlier age at 5% egg production than PS20 and PS22 (P = 0.003). The interval from photostimulation to age at 5% egg production in PS20 and PS22 was shorter than in other treatments (P = 0.005). Later peak egg production was seen in PS20 (211.0 D) and PS22 (218.0 D) than in PS16 (183.0 D) and PS18 (190.0 D, P = 0.020), but the laying rate of PS20 decreased slowly after peak laying. PS20 and PS22 had higher egg weights than PS16 and PS18 at peak laying (P = 0.018). Age at photostimulation had no effect on egg number, defective egg number, or hatchability (P > 0.05). In summary, the onset of lay can be advanced by photostimulation at early ages, but there is no difference on egg production until 51 wk. Photostimulation at 20 wk improves peak of laying and laying uniformity.