The Timing of the Maternal Recognition of Pregnancy Is Specific to Individual Mares.
Authors: Newcombe John R, Cuervo-Arango Juan, Wilsher Sandra
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Maternal Recognition of Pregnancy Timing in Mares Individual mares appear to possess a characteristic "window" for maternal recognition of pregnancy (MRP), with the timing of this critical physiological shift varying significantly between animals but remaining consistent within each individual mare. Researchers performed embryo reductions on singleton and twin pregnancies at specific intervals between days 10–14 post-ovulation across 10 mares (150 singleton and 9 twin pregnancies total), recording when luteostasis—maintenance of the corpus luteum and failure to return to oestrus—reliably occurred; they also tracked interovulatory intervals in non-pregnant cycles for comparison. The earliest MRP occurred at 252 hours post-ovulation (mid-day 10), but the threshold for consistent luteostasis varied considerably between individual mares across a 72-hour range (272–344 hours), with statistical analysis confirming a significant individual mare effect independent of embryo vesicle diameter or singleton versus twin status. These findings have important implications for breeding programmes and fertility management: recognising that mares have individual MRP signatures may help explain variable responses to embryo manipulation techniques, guide timing of early pregnancy interventions, and inform decision-making around twin reduction protocols. Future research into the underlying hormonal and molecular mechanisms driving this individuality could refine assisted reproductive strategies and improve outcomes in problem mares.
Read the full abstract on PubMed
Practical Takeaways
- •When performing embryo reduction procedures, recognize that the critical window for maintaining pregnancy (achieving luteostasis) is individual to each mare and cannot be predicted from standard parameters like embryo size
- •Individual mares show consistent MRP timing across multiple pregnancies, suggesting potential value in tracking each mare's historical response patterns to optimize embryo reduction timing
- •Embryo reduction success depends more on the specific post-ovulation timing and individual mare factors than on whether the pregnancy was singleton or twin, or on embryo vesicle diameter
Key Findings
- •The timing of maternal recognition of pregnancy (MRP) varies between individual mares, ranging from 252 h to 344 h post-ovulation (days 10-14)
- •Each individual mare shows repeatable timing of MRP when embryo reduction is performed at consistent intervals
- •Binary logistic regression confirmed significant individual mare effect (p < 0.001) and post-ovulation interval effect (p < 0.001) on luteostasis, but vesicle diameter and singleton vs twin pregnancy had no significant effect
- •Median interovulatory interval varied significantly between mares (p < 0.05) but was not correlated with MRP timing