Effect of dose and day of treatment on uterine response to oxytocin in mares.

The research article focused on establishing the correlation between the dose and timing of oxytocin treatment on intrauterine pressure in mares. The results indicated that oxytocin administration prior to ovulation produces a more intense response, which decreases after ovulation. The intensity of this response can, however, be compensated for with an increased dose of oxytocin.

Methodology and Data Collection

• The research involved six normal mares which were subjected to two different strengths of oxytocin treatment. These were administered two days before ovulation, on the day of ovulation, and two days after ovulation.
• Intrauterine pressure (IUP) was measured using micro-tip-catheters. One catheter was placed within the uterus, while two others acted as reference sensors in the mare’s vagina and external region. The catheters transmitted data via telemetry for a duration of 30 minutes to set a baseline before saline was administered intravenously.
• An additional 30-minutes recording was made after saline administration. Oxytocin was then injected, and IUP was recorded for a subsequent 60 minutes.

Experiment Results and Conclusion

• The study found that there was no change in IUP after the saline was injected. However, the administration of both 10 and 25 IU oxytocin doses produced a response. The intensity of the reaction was dependent on the day of administration and the dose of oxytocin.
• The response variance was notably higher after the administration of 10 IU oxytocin compared to 25 IU oxytocin. The uterine response was highest on Day 2 before ovulation and lowest on Day 2 after ovulation.
• The researchers also identified a negative correlation between the uterine response and increasing plasma progesterone levels. There was, however, no correlation between the uterine response and plasma estradiol-17beta concentration.
• In summary, the study shows that administering oxytocin to mares before ovulation yields a higher response than after ovulation. However, a decreased response intensity after ovulation can be compensated for by a higher oxytocin dose. The research also signified the efficacy of the multiple catheter technique for assessing changes in uterine pressure.