Factors affecting the incidence of postpartum oestrus, ovarian activity and reproductive performance in Thoroughbred mares bred at foal heat under Indian subtropical conditions.

The research article explores the impact of environmental conditions and other factors on the post-birth sexual activity, ovarian activity, and overall reproductive performance of Thoroughbred Mares, especially during the Foal Heat (FH) stage, in subtropical north-western India.

Explanation of the Research

• The researchers analysed the reproductive records of 228 Thoroughbred mares over 694 mare years. In approximately 93% (645/694) of cases, overt heat activity was seen within 21 days post-birth.
• In a significant finding, mares that foaled in April were more likely to display this postpartum heat activity than those foaling earlier in the year (January and February).
• Multiparous mares, or those having given birth more than once, were less likely than primiparous ones to fail in demonstrating heat activity post-birth.
• The research further monitored 190 mares to ascertain the timing of the Foal Heat phase and first ovulation. Here, it was found that regardless of the month, the stud farm, year or mare’s parity, the onset of FH or first ovulation was not affected. This was also the case for the interval between the onset of FH and ovulation.

Post-birth Reproductive Performance

• The Day 16 pregnancy rate for mares bred during the Foal Heat phase was found to be just under 54%, with an overall foaling rate of roughly 46% – similar to mares bred later after giving birth. This indicates that the timing of conception did not appear to affect pregnancy or foaling rates.
• However, the mare’s age was found to significantly impact Foal Heat pregnancy rates, with a higher age leading to lower rates.
• Additionally, mares that underwent uterine treatment had significantly lower Day 16 pregnancy rates than untreated ones. Upon examination, this difference was only present during the initial cycle postpartum.

Conclusion

• In conclusion, factors such as the environment (specifically subtropical climate) appeared to influence post-birth sexual and ovarian activity, causing a delay compared to those in temperate climates.
• However, performing at the Foal Heat stage and the factors influencing sexual activity post-birth were similar, regardless of the environment. This suggests a level of environmental adaptation in these Thoroughbred mares’ reproductive behaviour.