Seasonality does not influence cortisol or testosterone production, or seminal quality of stallions located at low latitudes.

The research article examines whether the different seasons affect testosterone or cortisol production and the quality of semen in stallions in low latitude regions, particularly in central Brazil. The study finds that, contrary to previous beliefs, the seasons do not impact these aspects of stallion reproduction.

Objective of the Study

• The study set out to examine if the production of hormones such as testosterone and cortisol, spermatogenesis, and the quality of fresh, chilled, and frozen semen in stallions varies with the seasons. The latitude they focused on for the study was 15°S, which is in central Brazil.
• The researchers aimed to identify the season more suited for semen cryopreservation in this specific latitude.

Methodology

• The study observed ten stallions over a period of one year, which was divided into two seasons: dry and rainy.
• Researchers analysed samples of fresh, chilled, and frozen-thawed semen. They used computer-assisted sperm analysis (CASA) and flow cytometry to assess semen samples.
• The study also calculated the temperature and humidity index (THI) to measure thermal stress, affecting the hormone levels and semen quality.

Findings

• The THI fluctuated between the two seasons, but researchers didn’t observe any thermal stress throughout the year. They also did not detect variances in stallions’ physiological parameters, or their plasma cortisol or testosterone levels between the seasons.
• The study didn’t find any significant difference in the total or progressive motility of sperm, sperm capacitation, and sperm membrane integrity. Even the count of live sperm with intact acrosomes and high mitochondrial membrane potential remained constant over the seasons in both fresh and frozen-thawed semen.

Conclusion

• The findings indicate that stallions’ semen can be effectively collected and cryopreserved throughout the year in central Brazil, irrespective of the seasons. The study provides a different perspective from previous research suggesting the seasonality impact on horse reproduction, specifically for low latitude regions like central Brazil.