Seasonality and freezability vs routine parameters in stallion semen.

The research explores the impact of seasonality and freezing on stallion semen quality. The findings suggest that sperm velocity, ATP content, and objective motility are not significantly affected by freezing, although ATP content drops by half after thawing.

Objective of the Research

• The main objective of this research was to analyze the fertility ability of stallion semen obtained during different seasons (June-July and October-November) and examine the effects of freezing on its various parameters including sperm velocity, ATP (adenosine triphosphate) content, and objective motility.

Methodology

• The study collected 30 ejaculates from 4 different stallions. Each of these samples underwent a standard analysis as well as assessments for ATP concentration, subjective and objective motility, and sperm velocity.
• The freezing process was carried out using the technique developed by Martin et al. in 1979. The sperm characteristics were compared before and after freezing.

Key Findings

• The study found that sperm velocity, ATP content, and objective motility in ejaculates with subjective motility more than 50% displayed values of 14.0+-0.84 µm s(-1); 4.8+-2.7×10(-7)M and 54.0 +-7.4%, respectively.
• For ejaculates with subjective motility less than 50%, these values were 8.4+-2.4; 0.74+-0.36×10(-7)M and 27.0+-0.8%.
• Interestingly, freezing did not lead to significant changes in these characteristics. However, the ATP content dropped to 50% after thawing, indicating some impact of the freezing process on ATP concentration in stallion semen.
• These characteristics showed a strong association (p<0.05) with some conventional parameters such as sperm motility, count, total spermatozoal number, and morphology.

Additional Observations

• Aside from the main findings, the study also analyzed sperm chromatin packing by decondensing sperm nuclei using a thiol reducing agent.
• This variable was not affected by freezing and appeared to rely on prolonged epididymal sperm storage during the non-breeding season. This led to excessive disulphur bridging in sperm basic proteins, potentially resulting in hypermaturation with faulty male pronuclear formation.