Luteal function in mares following administration of oxytocin, cloprostenol or saline on day 0, 1 or 2 post-ovulation.

This study investigates how the administration of different substances (saline, oxytocin, or cloprostenol) to mares after ovulation affects luteal function. It found that repeated administration of cloprostenol could negatively impact pregnancy outcomes but could also be effective in breaking down the luteal structure when mares are not bred.

Research Objectives and Methodology

• The study aimed to understand the impact of administering different substances (saline, oxytocin, or cloprostenol) to mares in the period after ovulation.
• Thirty mares were treated with these substances in various doses and at different times (Day 0, 1, or 2 post-ovulation).
• The study assessed the effect of these treatments on the interovulatory interval and circulating progesterone concentrations at different times.

Key Findings

• The study found that the interovulatory interval for control cycles (those treated with saline) was roughly 22.7 days, with a range of about 20.6 to 23.8 days across all treatment groups.
• Mares that received two micro-doses of cloprostenol on Day 2 after ovulation exhibited the shortest interovulatory period. This group also had the lowest mean circulating progesterone levels on Days 3 to 7 and on Day 13, and it took the longest time for them to reach concentrations of 5 ng/ml.

Conclusions

• The data suggests that administering cloprostenol repeatedly in the early post-ovulatory period may more effectively impair luteal function than single doses.
• This impairment of the luteal function could negatively impact the chances of successful pregnancy. However, it could also be beneficial in breaking down the luteal structure when mares are not bred.