Authors: Ferré Luis B, Jaeschke Julian, Gatti Juliana, Baladón Gerardo, Bellocq Ezequiel, Fernández Gustavo, Rearte Ramiro, Kjelland Michael E, Colazo Marcos G, Thomas Jordan M
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary GnRH-based fixed-timed artificial insemination (FTAI) protocols may offer a viable alternative to the oestrogen-dependent approaches currently dominating South American beef cattle breeding programmes, particularly for grazing, lactating Bos taurus cows where reproductive efficiency directly impacts herd profitability. Across two large-scale experiments (235 and 462 animals respectively), researchers compared four protocol variants combining intravaginal progesterone devices with either oestradiol esters or GnRH, measuring plasma progesterone concentrations, corpus luteum presence at device removal, and pregnancy rates per AI. GnRH-based protocols consistently outperformed oestrogen-based treatments, with significantly elevated progesterone levels and corpus luteum development, whilst the 7&7 GnRH protocol—incorporating pre-synchronisation with prostaglandin—yielded the highest pregnancy rates across both trials. For practitioners managing grazing herds where oestrogen availability or regulatory constraints may be limiting factors, these findings suggest GnRH-based FTAI protocols warrant serious consideration as they deliver equivalent or superior reproductive outcomes without dependence on oestradiol compounds, potentially improving both animal welfare compliance and breeding programme sustainability in extensive production systems.
Read the full abstract on PubMed
Practical Takeaways
- •GnRH-based synchronization protocols can replace estrogen-based protocols in beef cattle breeding programs with equal or superior fertility outcomes
- •The 7 & 7 GnRH protocol (with PG pre-treatment and dual GnRH doses) should be considered the preferred option for maximizing pregnancy rates in postpartum suckling cows
- •Protocol selection may depend on product availability and cost in different regions, as GnRH alternatives now have proven efficacy comparable to established estrogen-based methods
Key Findings
- •GnRH-based FTAI protocols produced greater pregnancy per AI compared to estrogen-based protocols in Experiment 1 (p < 0.01)
- •The 7 & 7 GnRH protocol achieved the highest pregnancy per AI rates in Experiment 2 (p < 0.01)
- •Cows receiving GnRH protocols had greater plasma progesterone concentrations and corpus luteum presence at IVPD removal compared to estrogen-based protocols
- •GnRH-based protocols offer a viable alternative to traditional estrogen-based FTAI protocols for grazing Bos taurus suckling beef cattle