Analysis of the pattern of ejaculation in stallions.

The research analyzes the ejaculation process of stallions, highlighting aspects like the pattern of mating behaviour, changes in pressure during copulation, the frequency of seminal jets, and key differences between early and later jets.

Mating Behavior and Copulation Pressure

• Researchers used an ‘open’ Krakl=o’w-72 Model artificial vagina to study the ejaculation process of stallions.
• The mating behaviour pattern was consistent in all observed copulations, where an average of seven intravaginal thrusts elicited ejaculation.
• The pressure within the artificial vagina’s vestibule changed as copulation progressed: it was around 66 mmHg at copulation start, increased to 142 mmHg just before ejaculation, and then decreased to 70 mmHg during semen emission.

Ejaculation Jets and Sperm Content

• The researchers found that the emission was considerably variable. They observed between five to ten “jets” of semen, with the average number being eight.
• Early jets of semen occurred under high pressure with a specific spattering effect. In contrast, later jets—which coincided with declining erection and penis retraction—were associated with lower pressure.
• The study found that the actual semen emission constituted only 24% of the total time of ejaculation, with the rest of the time comprising the intervals between successive seminal jets.
• The first three jets contained about 80% of the total number of ejaculated spermatozoa.
• There was a gradual decrease in the total number of spermatozoa, along with the ergothioneine content, in the successive jets.

Bacterial Growth

• No bacterial growth was found when the sperm-rich fraction of the semen was inoculated on solid media, indicating a lack of bacterial presence in the ejaculate.