Serum prolactin and luteinizing hormone levels during an induced pause in domestic fowl.

Serum prolactin (PRL) and luteinizing hormone (LH) levels were measured in White Leghorn hens induced to pause by fasting and exposure to 8L:16D photoschedule. Both PRL and LH levels declined during the fast and increased upon refeeding. Prolactin levels changed primarily in response to the fasting/refeeding component of the pause-inducing procedure, as exposure of non-fasted hens to an 8L:16D photoschedule exerted little effect on serum PRL levels. Injections of ovine prolactin during the pause-inducing procedure significantly reduced the subsequent rate of loss of primary wing feathers, suggesting that in certain physiological states, PRL may function to suppress molting.