p- and m-Cresols emitted from estrous urine are reliable volatile chemical markers of ovulation in mares.

This research suggests that two compounds found in horse urine, m- and p-cresols, can be used as reliable markers to predict ovulation, potentially simplifying and making the insemination process more cost-effective.

Sample Collection and Analysis

• The study involved collecting urine samples from 14 mares of five different breeds during their estrus and diestrus phases.
• The researchers used a technique known as “solid phase micro extraction” to collect about 150 volatiles (gaseous or easily vaporizable substances) from the head-space samples of the urine.
• The volatiles collected were then analyzed using gas chromatography-mass spectrometry methods to compare the chromatographic profiles of the volatile substances.

Significant Findings

• From the analysis, it was found that during estrus, the concentrations of m- and p-cresols were significantly higher. Conversely, diethylphthalate was more abundant during diestrus.
• When the m- and p-cresols were monitored a few days before, during, and after estrus, it was observed that their concentrations began to increase 3-4 days before ovulation, peaking a day before ovulation.
• On the day of ovulation, the concentrations of these metabolites dropped sharply to almost basal levels, and remained so for six days after ovulation.
• In the case of four mares, changes in the concentration of diethylphthalate were less pronounced and more variable over time compared to the cresols.

Potential Implications of the Study

• The findings of this study suggest that by monitoring the levels of m- and p-cresols in the urine of mares, it could be possible to predict the time of ovulation.
• The ability to accurately predict ovulation would allow more precise timing of insemination, which could save time and reduce costs.
• Given that the procedure does not involve invasive techniques and uses urine samples, it also has the potential to simplify the whole process.

For these reasons, the authors suggest that m- and p-cresols could serve as reliable chemical markers for ovulation in mares. However, more research is likely needed to confirm these findings and to develop a practical method of using these markers in real-world settings.