Effect of sulfadiazine and pyrimethamine on selected physiologic and performance parameters in athletically conditioned thoroughbred horses during an incremental exercise stress test.

The research investigates the impact of common medications – sulfadiazine and pyrimethamine – on the physiological and performance parameters of thoroughbred horses. It finds that their administration does not affect athletic performance, although minor effects are noted in some blood and serochemical measurements.

Research Methodology

• The medications sulfadiazine (20 mg/kg) and pyrimethamine (1mg/kg) were given orally to 12 physically fit thoroughbred horses daily for four consecutive days. This is the same regimen used to treat equine protozoal myeloencephalitis, a neurological disease in horses.
• The horses were randomly divided into two groups for testing purposes in a crossover design. This design meant that each horse acted as its own control, adding to the validity of the study’s findings.
• An incremental exercise stress test was conducted until the horses reached the point of exhaustion. This stress test was likely chosen to assess the effect of the medication on the horses’ maximum performance capacity.

Findings

• Interestingly, there was no observable impact on the horses’ athletic performance resulting from the sulfadiazine/pyrimethamine treatment. This suggests that the administration of these medications does not detrimentally affect a horse’s ability to perform physically.
• Some minor effects were detected in specific hematologic and serochemical measures, including decreased total white blood cell counts (indicating a potential reduction in the horses’ immune response), red blood cell distribution width (an indication of variability in red blood cell size), total hemoglobin (a protein in red blood cells that carries oxygen), serum sodium and serum chloride (two essential electrolytes).
• The sulfadiazine/pyrimethamine treatment also significantly decreased the concentration of folic acid in the horse’s blood serum. A key nutrient in red blood cell formation, this drop is a crucial finding requiring further research.

Implication and Significance

• The study’s findings are important for understanding the physiological impacts of sulfadiazine and pyrimethamine on racehorses. Despite not affecting athletic performance, the minor changes in hematological and serochemical parameters may have implications for horses’ overall health, particularly in relation to immune function and nutrient levels.
• Future research should focus on long-term studies to better understand the implications of these changes and whether they may have other significant effects on health, performance and overall wellbeing of horses.