THE ONTOGENY AND CONTROL OF INCUBATION BEHAVIOR IN TURKEYS

As a consequence of its fundamental role in avian reproduction, incubation behavior has been of great interest to scientists and to turkey breeders and producers of hatching eggs. Incubation behavior in turkey hens continues to be a major hindrance to enhanced reproductive performance in the domestic turkey, resulting in substantial loss of potential egg production. The onset and maintenance of incubation behavior is dependent upon a series of obligatory factors. Nest entry induced by progesterone surges in laying hens, which is dependent on prior estrogen priming, is a prerequisite for prolactin (Prl)-induction of incubation behavior. Thereafter, persistent nesting stimulates Prl secretion and elevated Prl levels maintain incubation activity. The increased Prl secretion in incubating hens is related to a diminished dopaminergic and an increased vasoactive intestinal peptidergic activities in the hypothalamus. An increase in Prl gene expression and Prl releasing capacity of the pituitary may also contribute to the hyperprolactenimic state in the incubating bird.