Corticosterone in ovo modifies aggressive behaviors and reproductive performances through alterations of the hypothalamic-pituitary-gonadal axis in the chicken.

ABSTRACT

Exposure to excess glucocorticoids during embryonic development affects offspring reproduction and suppresses the hypothalamic-pituitary-gonadal (HPG) axis in mammals. However, whether corticosterone (CORT) causes similar effects in the chicken remains unclear. In the present study, we injected low (0.2µg) and high (1µg) doses of CORT in ovo before incubation and detected changes in aggressive behavior, tonic immobility (TI), reproductive performances, and HPG axis gene expression in posthatch chickens of different ages. High dose of CORT suppressed growth rate from 3 weeks of age, increased the frequency of aggressive behaviors, which was associated with elevated plasma CORT concentration. High-dose CORT significantly (P<0.05) down-regulated arginine vasotocin (AVT), corticotropin-releasing hormone (CRH), 11ß-hydroxysteroid dehydrogenase type 2 (11ß-HSD2) and gonadotropin-releasing hormone 1 (GnRH1), while significantly (P<0.05) up-regulated gonadotropin-inhibitory hormone (GnIH) and 11ß-HSD1 mRNA expression in the hypothalamus. Glucocorticoid receptor (GR) and 20-hydroxysteroid dehydrogenase (20-HSD) mRNA levels were not affected by CORT treatment. High-dose CORT significantly (P<0.05) reduced egg production and egg quality, which was associated with decreased ovary and oviduct weight. Moreover, CORT exposure significantly decreased (P<0.05) luteinizing hormone (LH) receptor and follicle-stimulating hormone (FSH) receptor mRNA abundance in theca cells of ovarian follicles 1 (F1), F2 and F3. In addition, yolk CORT concentration was significantly higher in eggs laid by hens prenatally exposed to high-dose CORT. Our findings suggest that in ovo administration of CORT programs the aggressive behaviors and reproductive functions in the chicken through alterations of HPG axis.