Fertility of prostaglandin-induced oestrus compared to normal post-partum oestrus.

This research aimed to investigate whether waiting longer before breeding horses after giving birth can potentially improve fertility rates. The study found no significant difference in fertility or fetal loss rates between mares bred on their normal post-partum oestrus and those given a prostaglandin analogue to delay breeding.

Study Methodology

• The study involved a total of 42 mares who were not bred during their normal post-partum oestrus (the cycle immediately following birth).
• These mares were instead given prostaglandins, a hormone-like compound, on the sixth or seventh day following ovulation. The use of prostaglandins induces oestrus, or a state of sexual receptivity, allowing researchers to delay breeding.
• The mares were then artificially inseminated with antibiotic-treated semen.
• The process was repeated for up to four more cycles if no pregnancy occurred.
• The study compared the results from these injected mares, using metrics such as cycles/pregnancy and rate of fetal loss, to results obtained from mares that were bred during 86 normal post-partum oestrous periods.

Study Findings

• The study showed that the onset of breeding and the duration of oestrus were longer in the injected mares compared to the untreated mares.
• However, both the treated (prostaglandin-injected) and untreated mares averaged 1.3 breeding periods per pregnancy, suggesting that fertility rates were similar in the two groups despite the altered timing.
• Additionally, the rate of fetal loss between the two groups showed no significant difference, meaning that the likelihood of a mare losing its pregnancy was similar whether the mare was bred immediately after giving birth or several cycles later.

Conclusion

• The research concluded that extending the interval from foaling (giving birth) to breeding does not improve the fertility in mares.
• This implies that interventions using prostaglandins to delay breeding in hopes of increasing fertility rates may not be effective.