Relationship between dose of cloprostenol and age of corpus luteum on the luteolytic response of early dioestrous mares: a field study.

This research examines the interplay between the dosage of the hormone cloprostenol and the age of the corpus luteum’s development in mares, and how these factors affect the process of luteolysis, a part of the estrous cycle. The study found that both the dosage of cloprostenol and the age of the corpus luteum significantly influence the occurrence of full luteolysis, particularly within a specific timeframe, but exceeding a certain dosage brings no additional benefit.

About the Study

• The study was conducted to understand the relationship between the dosage of cloprostenol, a drug that induces luteolysis, and the age of the corpus luteum, the temporary endocrine structure involved in ovulation and early pregnancy stages.
• Four different doses of cloprostenol (37.5, 250, 500 and 750 μg) and five age ranges of the early corpus luteum (80, 88, 96, 104 and 112 hours) were evaluated with regards to their effect on the occurrence of luteolysis in mares.

Study Findings

• The results indicated that both the given dose of cloprostenol and the age of the Corpus Luteum (CL) at the time of treatment significantly affect the percentage of mares undergoing full luteolysis.
• The efficacy of the 37.5 μg dose was found to be similar to that of the 250 μg dose, while the 500 μg dose showed similar effects to the 750 μg dose. This indicates diminishing returns at higher doses.
• The study found that higher doses of cloprostenol (500 and 750 μg) induced full luteolysis more frequently than lower doses (37.5 and 250 μg), but only in the 96-104 hour post-ovulation timeframe. Outside this timeframe, the dose did not significantly alter luteolysis frequency.
• No effect of the age of the corpus luteum or cloprostenol dose on the interovulatory interval was discovered, meaning these factors did not influence the time between ovulations.

Conclusions

• The main conclusion drawn from the research is that the effect of cloprostenol on the percentage of mares undergoing full luteolysis is dose-dependent, but this is only true for mares with corpus luteum aged between 96 to 104 hours.
• No advantage was found in administering more than 500 μg of d,l-cloprostenol, as the frequency of full luteolysis in mares didn’t increase with doses beyond this amount.