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 chi cks for eggs disrupt incubation; prolactin levels decrease whereas lut einizing 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 hen s), or both (maternal nest-deprived hens), on the behavior and hormone concentrations of incubating hens. The results confirm that nest remo val, as well as adding chicks, stops incubation. No differences were f ound between maternal and maternal nest-deprived hens' behavioral resp onses or hormonal concentrations. These results do not support the hyp othesis that the drop of plasma prolactin observed in maternal hens is the consequence of the nest abandonment. In contrast, nest-deprived h ens presented lower concentrations of prolactin and higher concentrati ons of estradiol than maternal and maternal nest-deprived hens. Moreov er, the nest-deprived hens presented lower concentrations of prolactin and higher concentrations of LH and estradiol than the hens given chi cks. We assume that physical contact with chicks, during brooding bout s, slows down the decrease of prolactin secretion and inhibits LH and estradiol release at the end of incubation.