Changes in Body Weight, Egg Production, Hackle Growth, and Plasma Sex Steroid Hormones and Prolactin during the Annual Reproductive Cycle in Domestic Geese

Abstract

This study was conducted to elucidate the changes in body weight, feather molts, hackle (cervical tract feather) growth, and plasma sex steroid hormones and prolactin in relation to annual reproductive cycle in adult domestic geese. Maximum body weight was observed in January (three of nine geese started laying), and gradually decreased during laying period (January to June). A positive correlation was observed between changes in food intake and body weight (r_s=0.81, P<0.01). Plasma concentration of estradiol started to increase in January and reached maximum levels in coincidence with the highest egg production which occurred in May. Estradiol concentrations showed a positive correlation with egg production (r_s=0.84, P<0.01). High levels of plasma concentrations of testosterone were observed from November to April. High levels of plasma progesterone were relatively confined to the second half of the laying period (April to June). Maximum prolaction concentration in plasma was observed in May, and was probably associated with broody behavior in two of the nine geese; this value was significantly greater than those observed in February, March, September and October (P<0.01). Changes in hackle growth showed a negative correlation with egg production (r_s=-0.90, P<0.01). The nadir in hackle growth was clearly coincident with maximal egg production.