Effect of long-term food restriction on pituitary sensitivity to cLHRH-I in broiler breeder females

The effect of long-term food restriction on the sensitivity of the pituitar y to exogenously administered chicken luteinizing hormone releasing hormone I (cLHRH-I) was investigated in three groups of broiler breeder females fe d ad libitum, fed a restricted quantity of food or fed a restricted quantit y of food to obtain an intermediate body weight between those of the first two groups. At 16 weeks of age, basal FSH release was higher in ad libitum fed birds, culminating in ovarian development and subsequent oestradiol pro duction by the small follicles. At this age, LH secretion was independent o f ovarian feedback factors. In all groups, cLHRH-I was most active in relea sing LH in intact and ovariectomized animals and, to a lesser extent, in re leasing FSH in ovariectomized birds. At 39 weeks of age, basal FSH concentr ations were similar among intact animals of all groups, whereas LH concentr ations differed among groups, with higher values in the restricted birds. T his food effect was enhanced in ovariectomized birds. Furthermore, the high response to cLHRH-I in the ovariectomized, restricted birds compared with the ad libitum, ovariectomized group suggests an improved sensitivity of th e hypothalamic-pituitary axis. In conclusion, birds fed ad libitum showed t he highest responsiveness to ovarian factors and to cLHRH-I in releasing FS H in the period before sexual maturity. No effect of amount of feeding coul d be observed for LH. However, during the egg laying period, LH release by cLHRH-I was highly dependent on amount of feeding and on ovarian feedback r egulation. This finding indicates that the amount of feeding can modify the sensitivity of the pituitary to cLHRH-I, and possibly to gonadal hormones, during the laying period.