Effect of successive ejaculation on stallion seminal characteristics.

This research investigates how consecutive ejaculations within an hour affect the seminal characteristics of stallions. It was found that several factors such as gel volume, total seminal volume, sperm concentration, and count per ejaculate decreased over successive ejaculations, especially after the first two or three instances.

Research Design and Procedure

• 32 sexually rested stallions were used for the study, which involved collecting five ejaculates at hourly intervals.
• Measurements were taken every time to evaluate changes in gel volume, total seminal volume, sperm concentration, and sperm count per ejaculate.
• The study also considered the age of the stallions, comparing ejaculates from 2- to 3-year-old stallions and those from 9- to 16-year-old stallions.

Significant Findings

• The study found significant declines in the gel volume, total seminal volume, sperm concentration and spermatozoa per ejaculate from the first to the second or third ejaculate.
• In contrast, gel-free seminal volume or percentage of motile spermatozoa did not show significant differences among the ejaculates.
• Younger stallions aged 2- to 3-years-old produced less volume and fewer spermatozoa compared to older ones aged 9- to 16-years-old.

Important Conclusions

• The study concluded that the most significant quantity of spermatozoa was represented in the first four ejaculates: 50% in the first, 74% in the first two, 86% in the first three, and 93% in the first four.
• A formula was derived to predict the number of spermatozoa obtained in five ejaculates, which involved multiplying the total number of spermatozoa in two successive ejaculates by 1.35 +/- 0.03.
• Despite certain fifth ejaculates containing as few as 0.02 X 10(9) motile spermatozoa, the average number of viable spermatozoa in the last extract from sexually rested stallions was significant enough (0.52 X 10(9)) to impregnate a mare during natural service.