Intrauterine administration of plant oils inhibits luteolysis in the mare.
Authors: Wilsher S, Allen W R
Journal: Equine veterinary journal
Summary
# Intrauterine administration of plant oils inhibits luteolysis in the mare Wilsher and Allen (2011) investigated whether oestrogen and fatty acids could suppress the natural decline of progesterone during the mare's oestrous cycle, prompted by ongoing uncertainty about the maternal recognition of pregnancy signal in equines. Their experimental design involved infusing either oestradiol in fractionated coconut oil, various plant and mineral oils, or control solutions directly into the uterine lumen of cycling mares at different timepoints post-ovulation, then tracking circulating progesterone levels to assess luteal persistence. Remarkably, fractionated coconut oil and peanut oil alone delayed luteolysis in 92% of mares when administered on Day 10 post-ovulation—a rate equivalent to oestradiol combined with coconut oil—whereas mineral oil proved ineffective (17% success rate), suggesting that oestrogen itself was not the critical factor and that specific plant-derived fatty acids were responsible for the effect. The timing of administration proved crucial, with Day 10 showing peak efficacy (92%), declining to only 25% success by Day 6 and 50% by Day 14 of dioestrus. For practitioners managing unwanted oestrous behaviour in non-breeding mares, these findings offer a practical, non-hormonal alternative: a single 1 ml intrauterine infusion of fractionated coconut or peanut oil during mid-dioestrus can reliably suppress oestrus by maintaining luteal function, whilst the mechanism—likely involving endometrial modulation of prostaglandin synthesis or release—warrants further investigation to optimise both this technique and our broader understanding of pregnancy recognition in mares.
Read the full abstract on PubMed
Practical Takeaways
- •Intrauterine infusion of fractionated coconut or peanut oil on Day 10 post-ovulation provides a practical, effective method to suppress unwanted oestrous behaviour through pseudopregnancy without pharmaceutical oestradiol
- •Timing is critical—Day 10 post-ovulation is optimal; treatment on Day 6 is significantly less effective, so practitioners must accurately identify ovulation timing
- •Mineral oil is ineffective and should not be substituted for plant oils, emphasising that specific oil composition (plant vs mineral) determines treatment success
Key Findings
- •Intrauterine administration of fractionated coconut oil or peanut oil on Day 10 post-ovulation delayed luteolysis in 92% of mares without requiring oestradiol
- •Peak efficacy occurred at Day 10 post-ovulation (92% success rate), with declining effectiveness on Day 6 (25% success rate)
- •Mineral oil did not prolong luteal lifespan (17% when alone, 25% combined with oestradiol), indicating plant oil composition is critical
- •Plant oils likely modulate prostaglandin synthesis or release from the endometrium rather than acting through embryonic oestrogen pathways