PSXIII-42 Plasma levels of growth hormone in laying hens in relation to developmental and hormonal factors

Abstract

Abstract Growth hormone (GH) is an important positive regulator of ovarian function in vertebrates, including birds, but it can accelerate aging processes. In the present study, GH levels in the blood of laying hens were investigated due to age, reproductive status and ovulatory cycle-related hormones. To this end, the following groups of hens were used: (1) young hens with long clutch (YLC, 29–31 week-old, >10 eggs per clutch), (2) YLC hens treated with LH (YLC-LH), (3) old hens with long clutch (OLC, 62–64 week-old), (4) old hens with short clutch (OSC, 3–6 eggs per clutch). The hens were sacrificed at 1.5 or 14.5 h after assumed ovulation as well as 3.5 h after the LH injection (n = 5–6 per each group). Plasma concentrations of GH were determined by RIA and those of ovarian steroid hormones were measured by ELISA. The data were analyzed by ANOVA. In all compared groups, levels of GH were similar at the beginning and the middle of the ovulatory cycle. The average concentration of GH in OSC hens was higher than in OLC hens (1.28±0.38 vs 0.39±0.09 ng/ml, P < 0.05) but did not differ from that in YLC hens (0.76±0.22 ng/ml). Furthermore, in OSC hens, a positive correlation (r=0.84, P < 0.05) was revealed between GH levels and testosterone levels in the middle of the ovulatory cycle. Injections of LH raised ovarian steroid concentrations (P < 0.001) and did not affect GH concentrations in the plasma of YLC hens. Meanwhile, GH levels correlated with estradiol-17β levels in the YLC-LH group (r=0.81, P < 0.05). The findings suggest that elevated plasma levels of GH are associated with a reproductive impairment in old hens. Besides, a relationship between GH and ovarian steroids depends on the hen age, reproductive status, ovulatory cycle stage, and LH impact. The study was supported partly by RFBR (19-016-00216).