Hormonal and Non-Hormonal Estrus Synchronization in Sheep and Goats: Physiological Basis, Efficacy, and Practical Applications

Efficient reproductive management is essential for optimizing productivity and sustainability in sheep and goat production systems. Estrus synchronization (ES) has emerged as a pivotal tool for coordinating mating, enhancing fertility, facilitating artificial insemination (AI), and supporting out-of-season breeding. Hormonal protocols, including progesterone devices, prostaglandins, and gonadotropin or gonadoliberine treatments, provide the highest precision in estrus and ovulation timing, with estrus response rates exceeding 90% and conception rates commonly between 65–85%. These methods are particularly effective in intensive or AI-based systems but are constrained by cost, labor, regulatory restrictions, and welfare considerations. Non-hormonal strategies, such as the ram effect, photoperiod manipulation, nutritional flushing, and management-based interventions, exploit natural physiological, socio sexual, and nutritional cues to partially synchronize estrus. While these approaches exhibit greater variability and lower precision than hormonal methods, they offer advantages in low input, organic, and extensive systems by improving reproductive clustering, ovulation, and lambing compactness. Among these, the ram effect is the most effective and widely applicable. Integrated reproductive management, combining hormonal or non-hormonal strategies with optimized nutrition, health, and flock management, is critical for achieving predictable and sustainable reproductive outcomes. Future research should focus on refining hormone-sparing protocols and enhancing the reliability of natural synchronization methods.