Influence of the presence of chicks on the ability to resume incubation behavior in domestic hens (Gallus domesticus).

In this study, hormonal and behavioral changes associated with nest deprivation in the absence or in the presence of chicks (replaced every day or not) were investigated in incubating hens. Prolactin levels decreased, whereas LH and E2 levels increased following nest deprivation. Surprisingly, the presence of chicks had no effect on prolactin changes. However, the presence of chicks significantly limited increases in plasma LH and estradiol. Furthermore, this inhibitory effect was greater when day-old chicks were replaced every day. On the other hand, the presence of chicks induced the emergence of specific maternal behavior, while, surprisingly, one-third of the nest-deprived hens without chicks continued to incubate. After a 3-day deprivation period, readiness to renest was maintained for a percentage of hens. Thus more than 2/3 of hens deprived of the nest for 3 days in the presence of chicks returned to their nests during the first day of being allowed to do so, versus less than 1/3 of hens without chicks among those that previously disrupted incubation behavior. Plasma prolactin concentrations of these renesting hens increased rapidly and reached again levels characteristic of incubating hens. We conclude that, under our experimental conditions, presence of chicks maintains readiness to incubate without maintaining high levels of plasma prolactin.