Abstract:

At the age of 20 week, 320 Hyline (Brown) commercial hens were randomly assigned into 8 groups, with 4 replications per group, 10 hens in each replication. According to abruptly and slowly increscent methods, the experiment was designed to 11L∶13D, 13L∶11D, 15L∶9D, 17L∶7D four photoperiods. At the end of 29 week, 2 hens were randomly selected from each replication, in order to detect the level of FSH, LH, P4 and E2.The results showed that FSH cooperate with LH, which could accelerate ovum to maturate and arose ovary secreting E2 and P4, then ovulating. 11L∶13D photoperiod group by slowly increscent method(GroupⅡ) had the highest surge level of FSH and LH. The higher hormone secretion was not related to the longer photoperiod.