Flaws in Estrus Synchronization Protocols Increase Vaginal Prolapse and Hydrometra Risk in Sheep

This study examines the reproductive outcomes of Lacaune crossbred ewes and hoggets under intensive production systems, focusing on vaginal prolapse and hydrometra associated with flaws in estrus synchronization (E.S.) protocols. Data from multiple farms were combined for analysis due to the absence of significant variation at the farm level. The findings revealed a strong association between vaginal prolapse, parity, and litter size, with hoggets carrying multiple fetuses facing the highest risk (p < 0.0001). This highlights the need to reconsider equine chorionic gonadotropin (eCG) administration in hoggets, as it increases the likelihood of multiple pregnancies and, consequently, prolapse. Additionally, a progressive rise in hydrometra prevalence was observed with repeated synchronization cycles in ewes, increasing from 0.51% after the third treatment to 12.33% after the fourth (p < 0.0001). Notably, in this study, the four synchronization cycles were applied over a relatively short period (7.22 ± 1.64 months), further supporting concerns that excessive hormonal treatments within a compressed timeframe exacerbate reproductive dysfunction. This pattern confirms that prolonged progesterone exposure can impair uterine function, leading to fluid retention and hydrometra, as previously reported. To mitigate these risks, adjustments in synchronization protocols—such as extending the interval between successive treatments—are necessary to safeguard reproductive health and enhance animal welfare. These findings underscore the importance of optimizing estrus synchronization strategies to balance productivity with the well-being of sheep in intensive farming systems.