Turkey Prolactin: Validation of a Radioimmunoassay and Measurement of Changes Associated with Broodiness

A sensitive and highly specific radioimmunoassay procedure has been developed for measuring levels of circulating turkey prolactin. Mean plasma prolactin levels in broody turkey hens were found to be 9 times those of laying hens and 23 to 50 times those of molting hens, male poults, and adult toms. The plasma prolactin concentration of laying hens was found to increase gradually beginning about 10 days prior to the onset of broodiness, and to increase sharply at about the time of persistent nesting. Interrruption of incubation behavior by nest-deprivation and constant light was associated with a precipitous decline in prolactin levels. A hen that continued to exhibit incubation behavior despite this treatment showed no decline in plasma prolactin levels. A hen that continued to exhibit incubation behavior despite this treatment showed no decline in plasma prolactin concentration. These results confirm and expand the findings of some other investigators that incubation behavior in the turkey is associated with dramatically elevated prolactin levels.