ABSTRACT: The hypothalamic-pituitary-gonadal (HPG) axis regulates egg laying through control hormones secretion in poultry. In this study, the serum hormones (12 samples per stage), serum biochemical indexes (12 samples per stage), and ovarian metabolites (8 samples per stage) of Muscovy breeder ducks were detected at prelaying stage (PT), start of laying stage (ST), high laying stage (HT), and the end of laying stage (ET). The serum hormones of Muscovy ducks were measured at 8:00, 13:00, 18:00, 23:00, and 4:00 within 1 d. The TG, TP, ALB, and GLB were significantly increased, while HDL-C was significantly decreased at ST as compared to PT (P < 0.05). Serum Na, Cl, Ca, P, and K showed significant rise at ST as compared to PT. Serum Na, Cl, Ca, and K were significantly declined, while P was significa
