Biology and Detection of Pregnanes During Late Gestation in the Mare

In late gestation mares, progesterone levels declined significantly, being metabolized into various pregnanes, with some reaching high concentrations. The study aimed to assess the impact of the 5α-reductase inhibitor dutasteride on pregnane metabolism and pregnancy outcomes, evaluate pregnane changes in mares with ascending placentitis using LC-MS/MS, and compare pregnane detection methods. Dutasteride altered pregnane metabolism without affecting pregnancy outcomes. LC-MS/MS provided more accurate pregnane measurements than immunoassays, which were confounded by cross-reactivity. The research highlighted the complexity of pregnane metabolism and the importance of LC-MS/MS for precise detection in late gestation mares.