INFLUENCE OF NEST DEPRIVATION ON BEHAVIOR, HORMONAL CONCENTRATIONS AND ON THE ABILITY TO RESUME INCUBATION IN DOMESTIC HENS (GALLUS-DOMESTICUS)

In this study, we investigated the influence of the length of nest dep rivation period (3 vs. 6 d) on the ability to renest of incubating hen s. We focused on the hens' behaviour, particularly on nesting and call s, on their prolactin, luteinizing hormone (LH) and oestradiol concent rations. Nest deprivation induced a drop of prolactin and an increase of LH plasmatic concentrations in hens. These changes in circulating p ituitary hormones were followed by changes in ovarian function: the pe rsistent rise of plasmatic oestradiol gave evidence of the resumption of ovarian activity. After nest deprivation, the number of clucks incr eased significantly and food calls appeared; these results demonstrate that 'maternal' calls can be emitted outside the maternal context Our results suggest that the onset of typical maternal calling is strongl y controlled by internal state such as plasmatic hormonal concentratio ns, independently of social stimulation. None of the 10 hens deprived for 6 d resumed incubation when given the opportunity, whereas, after a 3 d deprivation period, three out of 10 hens renested and two hens i ncubated sporadically and then gradually abandoned their nests. Long p eriods of nest deprivation appear to disrupt the habits of sitting and nesting. Before nest reopening, all the hens presented low levels of plasmatic prolactin. Plasma prolactin concentrations of the renesting hens increased after nest boxes were reopened and returned to levels f ound in incubating hens. We suggest that pituitary prolactin rather th an plasmatic prolactin is responsible for the maintenance of incubatin g potential in hens deprived of their nests.