Efficiency of CIDR-Based Protocols Including GnRH Instead of eCG for Estrus Synchronization in Sheep.
Authors: Martinez-Ros Paula, Gonzalez-Bulnes Antonio
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Synchronising oestrus in meat sheep is essential for efficient flock management, yet the most common protocols rely on equine chorionic gonadotrophin (eCG), which carries regulatory and practical limitations. Martinez-Ros and Gonzalez-Bulnes compared three CIDR-based synchronisation strategies in Segureña ewes: conventional CIDR-eCG treatment against two GnRH protocols (single GnRH dose at CIDR removal, or dual GnRH doses flanking the CIDR insertion and removal). Oestrous expression rates were robust across all groups (84–90%), with equivalent ovulation rates, though the dual-GnRH protocol produced tighter synchronisation of ovulation timing—a notable advantage for fixed-time artificial insemination protocols, as the narrower ovulation window reduces the need for repeated breeding attempts. Whilst eCG triggered earlier onset of oestrous behaviour and the preovulatory luteinising hormone surge, the functional reproductive outcomes were comparable, suggesting GnRH-based alternatives warrant serious consideration where eCG availability or cost is problematic. For practitioners managing intensively bred or assisted-reproduction programmes, these findings indicate that a two-dose GnRH strategy could substitute for eCG without sacrificing fertility, potentially improving scheduling predictability through superior synchronisation of the ovulatory window.
Read the full abstract on PubMed
Practical Takeaways
- •For sheep producers using estrus synchronization: GnRH-based protocols with two doses offer comparable breeding outcomes to traditional eCG protocols while potentially providing better ovulation timing consistency
- •The two-dose GnRH approach (at CIDR insertion and 56h post-removal) may be preferable when tighter synchronization of ovulation is desired, despite slightly later estrus onset than eCG
- •Substituting GnRH for eCG in CIDR-based protocols is a viable alternative that may reduce reliance on equine-derived products while maintaining fertility outcomes
Key Findings
- •Estrus behavior appearance rates were 84-90% across all treatment groups with subsequent ovulation in all ewes showing estrus signs
- •CIDR-eCG protocol induced earlier onset of estrus behavior compared to single-dose and dual-dose GnRH protocols (p < 0.05)
- •GnRH-CIDR-GnRH (two-dose) protocol produced narrower range of ovulation timing, indicating superior synchronization of follicular growth (p < 0.05)
- •Two-dose GnRH protocols achieved similar reproductive yields to eCG-based protocols