Multiple site electromyography recordings of uterine activity following an intrauterine bacterial challenge in mares susceptible and resistant to chronic uterine infection.

This research examines the differences in myometrial activity in mares susceptible and resistant to chronic uterine infection, following a bacterial challenge. The results suggest increased myometrial activity in resistant mares, which could signify its role in the uterine defense mechanism.

Objective of the Study

• The purpose of this research was to investigate the electrical myometrial activity in mares with different susceptibilities to chronic uterine infection (CUI).
• The study aimed to understand how myometrial activity changes in response to a bacterial challenge and to uncover if these changes differ between mares more or less susceptible to CUI.

Methods Used in the Study

• Six mares were chosen for the study – three of them known to be more susceptible to CUI, and the other three considered resistant to CUI.
• Electrodes were implanted surgically in the myometrium of these mares to monitor electrical activity.
• To confirm the mares were in their oestrus stage, they used transrectal ultrasonography of the reproductive tract and teased the mares with a stallion. This confirmation was also supported by blood progesterone concentrations of less than 0.1 ng ml-1.
• At the third day of oestrus, or when a follicle larger than 35 mm was detected, the researchers introduced 5 x 10(6) Streptococcus zooepidemicus into the uterus.
• The myometrial electrical activity was closely monitored before and after the bacteria infusion until stabilization.

Results of the Study

• No significant differences were detected in the myometrial electrical activity between the two sets of mares prior to the bacterial infusion.
• Post bacterial infusion, all mares showcased an increase in myometrial electrical activity, but the response was different between resistant and susceptible mares.
• The resistant mares demonstrated higher myometrial activity than those mares more susceptible to CUI. This was marked in terms of frequency, duration, and intensity of uterine activity, especially between 10 and 20 hours after the bacteria were introduced.

Conclusion of the Study

• The findings suggest that myometrial activity might play a crucial role in the uterine defense mechanism against infection, showing greater activity in mares that are resistant to CUI.
• Furthermore, the results provide insight into the varied uterine response to bacterial invasion in mares with different susceptibilities to CUI.