Sexual maturation, serum steroid concentrations, and mRNA expression of IGF-1, luteinizing and progesterone hormone receptors and survivin gene in Japanese quail hens

In avian species, sexual maturation represents the evidence of start laying, which is a consequence of the development of ovarian follicles. These follicles are the functional reproductive unit whose maturation and viability critically depends on endocrine, paracrine, and autocrine factors beyond the signals from the central nervous system. The present study was undertaken to investigate the correlation of sexual maturity with tissue growth, mRNA expression of certain genes, and serum steroid concentrations in Japanese quail hens. To carry out the present study, a total of forty Japanese quail hens (5 weeks) were housed individually under uniform husbandry condition with ad libitum quail layer ration and water at 14-hour photo schedule. On sixth week onwards, four birds were sacrificed at each time on 1, 3, 7, 10, 13, 16, 19, 22, 25, and 28 days. Serum was extracted aseptically to analyze the gonadal steroid hormones (estrogen and progesterone) and corticosterone to investigate the liaison with sexual maturation of the species. Expression analyses of four genes i.e., insulin-like growth factor-1, luteinizing hormone receptor, progesterone receptor, and survivin were carried out in the three largest ovarian yellow follicles. A significant (P < 0.05) increase in body weight gain and oviduct weight was recorded during the phase of sexual maturation. Smaller follicles revealed higher insulin-like growth factor-1 and survivin gene expression, whereas the reverse result was manifested in both the luteinizing and progesterone hormone receptors. In biochemical study, the gonadal steroids (estrogen and progesterone) were recorded higher at the first half of the experiment when a gradual decrease in corticosterone concentration was confirmed from the very beginning of this study. This result substantiated that sexual maturation in Japanese quail may be completed by the time of 8 weeks after its birth in support of the analyzed information studied in the current investigation.