Respective effects of chicks and nest on behavior and hormonal concentrations of incubating domestic hens.

Removal of incubating hens from their nestboxes or substitution of chicks for eggs disrupt incubation; prolactin levels decrease whereas luteinizing hormone and gonadal steroid concentrations tend to rise. The present experiment was undertaken to determine the relative influence of removing the nest (nest-deprived hens), adding chicks (maternal hens), or both (maternal nest-deprived hens), on the behavior and hormone concentrations of incubating hens. The results confirm that nest removal, as well as adding chicks, stops incubation. No differences were found between maternal and maternal nest-deprived hens' behavioral responses or hormonal concentrations. These results do not support the hypothesis that the drop of plasma prolactin observed in maternal hens is the consequence of the nest abandonment. In contrast, nest-deprived hens presented lower concentrations of prolactin and higher concentrations of estradiol than maternal and maternal nest-deprived hens. Moreover, the nest-deprived hens presented lower concentrations of prolactin and higher concentrations of LH and estradiol than the hens given chicks. We assume that physical contact with chicks, during brooding bouts, slows down the decrease of prolactin secretion and inhibits LH and estradiol release at the end of incubation.