Effects of injected ovarian steroids on reproductive patterns and performance in post-partum mares.

The research investigates the impact of treated foaling mares with progesterone and oestradiol shortly after giving birth, pointing out a delay in ovulation, but no apparent advantage in reproductive performance compared to conventional management practices.

Objective of the Study

• The central aim of this study is to assess the effects of injecting two types of ovarian steroids – progesterone and oestradiol – on the reproductive patterns and performance of post-partum (after childbirth) horses, specifically mares that have just foaled (given birth to a foal).

Research Methodology and Findings

• The study involved administering daily doses of 150 mg of progesterone and 10 mg of oestradiol to mares within 12 hours after they had given birth.
• Recent evidence showed that this treatment led to a delay in ovulation averaging 5.3 additional days compared to mares that did not receive the hormone injections.
• The ovulation delay was recorded at 15.6 +/- 2.6 days in treated mares versus 10.3 +/- 2.4 days in untreated mares.
• However, when the treated mares were mated following this delay, the researchers did not observe any improvement in their reproductive performance compared to those mated using standard, non-drug-influenced management.

Insights on Gonadotrophin Secretion

• The study found that gonadotrophin secretion – the release of a type of hormone that stimulates the growth and function of the gonads (ovaries in female animals) – was inhibited during treatment with progesterone and oestradiol.
• After the treatment was complete, observed gonadotrophin secretion patterns returned to mirror those seen during normal oestrous (heat) periods.

Implications

• The findings of this study suggest that while administering certain ovarian steroids to post-partum mares can manipulate aspects like timing of ovulation, this form of treatment does not necessarily enhance the mares’ reproductive performance.