Effect of teasing, mechanical stimulation and the intrauterine infusion of saline on uterine contractions in mares.

This study explores how different stimuli during coitus, such as teasing by a stallion, mechanical stimulation, and intrauterine infusion of saline, can affect uterine contractions in mares. It suggests that the contractions, which are crucial for sperm transportation and ejaculate elimination, vary depending on certain stimuli applied.

Research Methodology

• The study utilized M-mode ultrasound technique to investigate uterine contractions, localized in both the uterine horns and the uterine body, under different coitus-related stimuli.
• The duration, amplitude, and count of the contractions were measured in mares during their oestrous cycle for 8 minutes total: 4 minutes before and 4 minutes after the various stimuli were introduced.
• The stimuli tested included teasing by a stallion, mechanical stimulation of the vagina and cervix, intrauterine infusion of sterile saline (80 ml, 10 ml, and 150 ml respectively) and the transcervical passage of a uterine catheter.

Main Findings

• Teasing by a stallion showed no significant effect on the number, amplitude, or duration of the uterine contractions.
• Mechanical stimulation increased the total number of contractions but had no impact on their duration or amplitude.
• An infusion of 80 ml of sterile saline increased both the quantity of contractions and their mean amplitude and duration in the uterine horns. However, such change was not observed in the uterine body.
• When using 10 ml of saline, there was a significant decrease in the number of contractions in the uterine horns, but not in the uterine body.
• The infusion of a larger volume of saline (150 ml) reduced the number of contractions in uterine horns, but it had no impact on the contractions’ amplitude or duration, and didn’t influence contractions in the uterine body.
• The insertion of a catheter into the uterus also resulted in fewer contractions in the uterine horns, with no effect on the body’s contractions or their duration or amplitude.

Conclusion

• The research shows that different coitus-related stimuli can have varying impacts on uterine contractions in mares.
• These findings hint at the complexity of the processes involved in fertilization and the factors that can influence the transportation of sperm and elimination of ejaculate in mares.