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

## TL;DR

This study shows that flawed estrus synchronization protocols in sheep increase the risk of vaginal prolapse and hydrometra, especially in young sheep carrying multiple fetuses.

## Contribution

The study identifies specific risks of estrus synchronization protocols in Lacaune-crossbred ewes and hoggets, particularly with repeated hormonal treatments.

## Key findings

- Hoggets carrying multiple fetuses have the highest risk of vaginal prolapse (p < 0.0001).
- Hydrometra prevalence increases with repeated synchronization cycles, reaching 12.33% after the fourth treatment (p < 0.0001).
- Prolonged progesterone exposure is linked to impaired uterine function and hydrometra.

## Abstract

This study examines the reproductive outcomes of Lacaune-crossbred ewes and hoggets in 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. The results corroborate previous reports that prolonged progesterone exposure can impair uterine function, leading to fluid retention and hydrometra. To mitigate these risks, estrus synchronization protocols should be critically reassessed—especially by extending the interval between successive treatments—to protect reproductive health and animal welfare. These findings not only underscore the need for more welfare-conscious practices in intensive sheep farming but also encourage further research aimed at refining hormonal management strategies in dairy ewe reproduction.