Failure of mammalian prolactin to induce incubation behavior in chickens and turkeys

Three experiments on a high-broody strains of chickens that had not been selected for egg production for 50 generations and one experiment on a commercial strain of turkeys were conducted to test the effectiveness of mammalian prolactin (NIH-S10) in inducing regression of the ovary and incubation behavior. In two experiments on chickens, environmental factors known to favor the expression of broodiness were provided, and four components of nesting or incubation behavior were monitored continuously during the light period with a closed-circuit television system and timelapse videotape recorder. Although all doses of prolactin used caused regression of large ovarian follicles, none induced incubation behavior in either chickens or turkeys. Some prolactin-injected chickens occasionally displayed the covering stance of maternal behavior. An explanation for the discrepancy between these results and the results of studies conducted more than 20 years ago, in which mammalian prolactin was highly effective in inducing incubation behavior in chickens, may lie in differences in purity of the prolactin preparations used.