Measurements of reproductive function in stallions treated with trimethoprim-sulfamethoxazole and pyrimethamine.

The research examined the impact of trimethoprim-sulfamethoxazole and pyrimethamine treatment on the reproductive functions of healthy pony stallions, finding that while the treatment did not affect semen quality, testicular volume, sperm production, or sexual desire, it did result in changes in copulatory ability and the strength and pattern of ejaculation.

Research Methods

• The study utilized a randomized complete block method to evaluate the potential effects of the treatment.
• A group of 12 mature pony stallions, all in good health, were included in the research.
• The stallions were divided into treatment and control groups, matched for age and diverse reproductive function traits.
• The treatment group was given trimethoprim-sulfamethoxazole and pyrimethamine for 90 days during summer and fall, while the control group was left untreated.
• Various aspects of reproductive function, such as semen characteristics, sexual behavior, testicular volume, and sperm production efficiency were monitored before treatment commenced and at 30-day intervals until 60 days after treatment conclusion.

Research Findings

• The findings indicated that there were no observable effects of the treatment on semen characteristics, testicular volume, sperm production efficiency, sexual desire, or the ability to achieve an erection.
• In the treatment group, 4 out of 6 stallions showed unusual conduct during copulation such as unsteadiness upon mounting, clumsy or weak thrusting, failure to flex the back, and thin or unnoticeable ejaculatory pulses leading to semen dribbling instead of powerful expulsion. These issues were noted 30, 60, and 90 days into the study.

Conclusions

• In light of the observations, the study concluded that despite treatment with trimethoprim-sulfamethoxazole and pyrimethamine not affecting semen quality, testicular volume, sperm production efficiency, or libido in healthy stallions, it could alter copulatory form and agility as well as the pattern and power of ejaculation.
• The study also advises that stallions which develop neurological signs during treatment should be used cautiously for breeding purposes.