Serum Progesterone and Conception Rates in Acyclic Embryo Recipient Mares Using a Bovine Progesterone-Releasing Intravaginal Device.
Authors: Rigoleto Júnior Wilson Luis, Dias de Camargo Neto Waldomiro, de Paula Nogueira Guilherme, Ferrari Tiago Augusto, Bertan Membrive Claudia Maria, Giometti Ines Cristina, Castilho Caliê
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Embryo transfer programmes commonly require acyclic recipient mares to have adequate progesterone support, but injectable protocols may not suit all operational circumstances. Researchers examined whether a bovine progesterone-releasing intravaginal device (1 g) could effectively prepare 24 acyclic recipient mares for embryo transfer, comparing conception outcomes and serum progesterone concentrations against 49 matched controls receiving standard long-acting injectable progesterone (1,500 mg). The intravaginal device substantially elevated serum progesterone from baseline (0.71 ng/mL) to therapeutically relevant levels by day 5 (4.09 ng/mL) and day 9 (6.45 ng/mL), with both formulations achieving comparable pregnancy rates of 83.33% and 73.46% respectively—a clinically meaningful result given the device's non-invasive delivery route. For practitioners managing embryo transfer programmes, particularly in situations where injectable administration presents practical challenges, the intravaginal device represents a viable alternative that achieves adequate endometrial priming without compromising conception rates. The findings suggest that progesterone delivery method matters less than achieving sufficient serum concentrations within the critical window around embryo transfer, though farriers and coaches should recognise that veterinary supervision of this protocol remains essential for optimal recipient selection and timing.
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Practical Takeaways
- •The intravaginal progesterone device is a viable alternative to injectable progesterone for preparing acyclic recipient mares for embryo transfer, with comparable conception rates (83.3% vs 73.5%)
- •Using the intravaginal device may offer practical advantages such as avoiding repeated injections while achieving adequate uterine progesterone levels within 5 days
- •This approach could be integrated into commercial embryo transfer programs as an equivalent or potentially preferred method for acyclic mare preparation
Key Findings
- •Intravaginal progesterone device increased serum progesterone from 0.71 ng/mL on D0 to 4.09 ng/mL on D5 and 6.45 ng/mL on D9 (P < 0.0001)
- •Pregnancy rate with intravaginal device (83.33%) was not significantly different from injectable long-acting progesterone (73.46%, P > 0.05)
- •Bovine intravaginal progesterone device effectively prepared the uterus of acyclic recipient mares for embryo transfer
- •Intravaginal route provides alternative delivery method to injectable progesterone for embryo transfer protocols