Effect of administering oxytocin or cloprostenol in the periovulatory period on pregnancy outcome and luteal function in mares.

This study examines the impact of administering oxytocin or cloprostenol to mares in the period immediately around ovulation on pregnancy outcomes and luteal function. The results indicate that either hormone can be administered without adversely affecting the chances of pregnancy.

Methodology

• 37 mares were included in the study. Their treatment began 4 hours after breeding and continued for two days post-ovulation.
• Oxytocin (20 units, injected intramuscularly) was used every 6 hours, while cloprostenol (250 micrograms, injected intramuscularly) was administered daily.

Findings

• The luteal function in the mares was impacted for several days following treatment. The luteal phase of a mare’s reproductive cycle refers to the period post-ovulation, wherein the body prepares for a potential pregnancy.
• Despite this temporary impairment, the treatment didn’t decrease the progesterone levels in the mares receiving cloprostenol to a degree that resulted in fewer pregnancies. Progesterone is a hormone crucial for the maintenance of pregnancy.
• The research found no significant difference between the two treatment groups in terms of pregnancy outcome by the 15th day post-ovulation. 13 out of 18 mares that received oxytocin became pregnant, while the number was 13 out of 19 for those administered cloprostenol. This is statistically equivalent with a P-value of 0.80 (P < 0.05 would indicate a significant difference).

Implications

• The results of the investigation suggest that cloprostenol can safely be used in post-breeding mares through to the second day after ovulation without decreasing the likelihood of successful pregnancy.
• This is significant for equestrian breeding programs as it suggests an alternative treatment method that doesn’t negatively impact pregnancy rates.