Effect of season on some characteristics of stallion semen.

The study found that season has a significant effect on various characteristics of seminal fluid and sperm in horses, including pH, protein levels, carbohydrates, dry weight, total nitrogen, lactic acid, and other factors in both first and second ejaculates. The effects were more pronounced on seminal plasma than on spermatozoa, and second ejaculates were generally more affected by season than first ejaculates.

Effect on Seminal Plasma

• The study observed a pronounced seasonal effect on seminal pH, refractometer ‘protein’, total carbohydrate, dry weight, total nitrogen (N2), and lactic acid in the seminal plasma of both first and second ejaculates.
• The effects on seminal plasma were greater than those on spermatozoa, indicating a more significant impact on the fluid surrounding the sperm cells.

Effect on Ejaculates

• Seasonal changes also influenced the total seminal volume, the number of spermatozoa per milliliter and per ejaculate, non-protein sulphhydryl, and glycerylphosphorylcholine in the second ejaculates.
• There was a seasonal difference in the concentrations of lactic acid in spermatozoa from the first ejaculates, and in total nitrogen from spermatozoa in the second ejaculates.
• Spermatozoa in the first ejaculates were less affected by seasonal changes than those in the second ejaculates.
• This differential effect on first and second ejaculates was generally true across all seminal characteristics studied, demonstrating a consistent pattern in how seasonal variations influence different aspects of seminal fluid and sperm cells.

Implications

• The findings of this study highlight the importance of considering seasonal variations when studying or managing reproductive health in horses.
• The differential impact on first and second ejaculates, as well as on seminal plasma versus spermatozoa, may have practical implications for breeding practices and reproductive research in equine science.