In mares resistant to endometrial infection, periovulatory treatment with ecbolic drugs does not influence uterine clearance or luteal development.

The article investigates the effects of specific drugs on luteal development and uterine clearance in mares after insemination during estrous. The study concludes that treatment of mares with clenbuterol or a synthetic variant of oxytocin known as carbetocin do not impair luteal development, uterine clearance, or overall pregnancy rates.

Objectives and Methods

• The goal of this research was to determine the relationship between experimentally impaired uterine clearance, treatment with ecbolic drugs, and luteal development in mares following insemination.
• The study was conducted in a crossover design format wherein eight mares were treated with four substances – saline (control), clenbuterol, oxytocin, and carbetocin, from the first day of insemination until two days after ovulation.
• The mares were given a rest period of one cycle between treatments to help in the recovery.
• Transrectal ultrasound tests were performed on the estrous mares to examine the presence of free intrauterine fluid, a common indicator of uterine inflammation or infection.
• Endometrial swabs were taken on the first and fourteenth day for cytology and bacteriology tests. Also, blood samples were collected daily to determine levels of progesterone and Prostaglandin F metabolites (PGFM).

Results and Analysis

• One mare was excluded from the study due to a uterine infection detected during the control cycle. For all other mares, only minor amounts of free intrauterine fluid were present after insemination, which decreased over time suggesting successful uterine clearance.
• The analysis found no significant interaction between the treatment and time, indicating the treatments had no detrimental effects on uterine clearance.
• In the cytology tests, there was no effect observed on the levels of polymorphonucleated cells due to the treatments, suggesting no induced inflammation.
• Secretion of PGFM, an indicator of luteal function, was also not influenced by any of the treatments, indicating no interference with luteal development.

Conclusion and Implications

• The researchers concluded that treating mares with clenbuterol or carbetocin does not impair uterine clearance or affect luteal development during estrous. Furthermore, it was found that that these treatments have no impact on the rates of successful pregnancy or conceptus size on day 14 after insemination.
• These findings are significant because they suggest that clenbuterol and carbetocin can potentially be used to manage reproduction in mares without causing detrimental effects on luteal function or uterine health.