Effect of age at photostimulation on sexual maturity and reproductive performance in rooster breeders

ABSTRACT The 2 × 4 factorial experiment was designed to determine the effect of strain and photostimulation age on sexual maturity and reproductive performance of rooster breeders. A total of 96 White Leghorn (WL) and 120 Beijing-You Chicken (BYC) roosters were randomly allocated to four treatments at 14 wk of age. The treatments represent photostimulation at 16, 18, 20, and 22 wk of age respectively (PS16, PS18, PS20, and PS22) in both strains. Photostimulation was achieved by increasing the day length from 8L:16D to 14L:10D and by increasing lighting intensity from 10 lx to 80 lx. Three birds from each interaction were sacrificed to characterize the comb and testes weights at four time points: 1 d before photostimulation and 2, 4, and 6 wk after photostimulation. Semen quality and hatching performance with the semen of the experimental roosters were measured at 30 and 45 wk of age, respectively. Results showed that the testes weight of PS20 and PS22 in WL and BYC was 6.4 and 2.9-fold higher than that of PS18 before photostimulation, while testes weight of PS18 in both strains increased sharply post photostimulation. The diameter of seminiferous tubules increased in the photostimulated roosters as compared to the non-photostimulated ones, and mature spermatozoa were produced four weeks after photostimulation and at 20 wk of age for PS16. The WL had lower semen volume and total sperm count than BYC (P 0.05). In addition, semen quality traits were not affected by age at photostimulation (P > 0.05) in both strains. The fertility, and hatching performance were not affected by strain or photostimulation age (P > 0.05). In summary, the sexual maturation of rooster breeders can be advanced by photostimulation at an early age, which does not lead to a difference in semen quality or hatching performance at adult stage.