The effects of intrauterine infusion of peanut oil on endometrial health, salivary cortisol and interovulatory period in mares.

This study investigates the impact of intrauterine infusion of peanut oil on the lengthening of dioestrus in mares, the associated side effects of the procedure and potential pain experienced by the mares. The findings suggest that peanut oil infusion does not statistically extend the luteal phase, but it does lead to an inflammatory response and increases in endometrial eosinophil numbers.

Study Objective and Design

• The research aimed to determine the impact of intrauterine infusion of peanut oil on equine endometrial health, assess whether the procedure was painful and confirm if peanut oil could extend the dioestrus period.
• For the study, six mares aged between 3 and 12 were used in a cross-over design, and each was administered with either 1 ml of intrauterine peanut oil or a sham treatment, on different ovulation cycles.

Measurements and Results

• The effects of the treatments were evaluated based on the interovulatory period, accumulation of uterine fluid as assessed by transrectal ultrasonography, serum progesterone levels, endometrial Kenney biopsy scores and histological features, endometrial eosinophil numbers, and salivary cortisol measurements.
• The results demonstrated the mare responses to intrauterine peanut oil infusion were inconsistent. The treatment did not statistically prolong the luteal phase or increase salivary cortisol levels. However, it caused superficial erosion of the endometrial surface epithelium in all mares and significantly upsurged eosinophil numbers in the endometrium.
• The Kenney grade for two out of the six mares temporarily worsened following the infusion.

Conclusions

• The findings showed that intrauterine peanut oil did not increase the duration of the luteal phase, but resulted in an inflammatory response and an increase in endometrial eosinophil numbers, suggesting a treatment-associated hypersensitivity-type reaction.
• The researchers recommend practitioners who consider using peanut oil to suppress oestrus to be aware of the legislative and regulatory implications of the procedure.