Steroid hormone content of seminal plasma influences fertilizing ability of sperm in White Leghorns.

Maternal and paternal influences before fertilization can significantly affect the ultimate reproductive output. In avian species, previous studies have shown that concentrations of testosterone (T) in seminal plasma vary greatly and are related to sperm quality. To our knowledge, the presence of other reproductive hormones in avian seminal plasma and their potential influences on fertility remain unstudied. We measured the concentrations of progesterone (P4), T, dihydrotestosterone, and estrogen in seminal and blood plasma collected from White Leghorn roosters. Progesterone was the most abundant hormone compared with all others measured, and concentrations of P4 in seminal plasma were significantly higher than concentrations found in circulation. Given the relatively high concentration of seminal plasma P4, we then attempted to determine its effect on fertility. Hens were inseminated with semen samples that were supplemented with either a high physiological dose of P4 or a control vehicle. Fertilization ability of all semen samples was then characterized using a perivitelline sperm hole penetration assay. Progesterone treatment significantly decreased the ability of sperm to reach and penetrate the egg, suggesting that males that deposit more P4 into seminal plasma may have a decreased capability to fertilize an egg.