Factors affecting plasma progesterone concentration and the retrospective determination of time of ovulation in cyclic mares.

The research investigates the variables influencing plasma progesterone concentration and the determination of time of ovulation in mares. The study discovers the role of several factors including time, multiple versus single ovulation, and season, but not luteal morphology, in affecting progesterone levels. It also successfully develops a method to retrospectively determine the time of ovulation in mares with high accuracy, albeit with some limitations.

Investigating Factors Influencing Progesterone Concentration

• The research was carried out on seven mares and studied plasma progesterone concentrations through daily blood samples. The collection and analysis identified clear trends in progesterone concentration that were used to fit two-phase logistic curves with a correlation coefficient of 0.98 suggesting a strong relationship.
• Time was found to be a significant factor affecting progesterone levels, with noticeable changes to levels occurring over the study period.
• There were also distinct variations among mares, specifically in the peak height of the progesterone plateau and in the area under the curve.

Effects of Ovulation and Season on Progesterone Concentration

• The researchers found that plasma progesterone concentrations were higher following multiple ovulations compared to a single ovulation. This highlights a direct relationship between the act of ovulation and resulting progesterone concentration.
• Season was also found to have a significant effect on progesterone concentrations, although the research did not detail specifics about which seasons resulted in higher or lower concentrations.
• The study did not note any significant effects of luteal morphology on plasma progesterone concentrations. This suggests that luteal morphology may not be a considerable factor in controlling or changing progesterone levels in mares.

Retrospective Determination of Time of Ovulation

• In additional to the original cohort, 25 more mares were studied to retrospectively determine the time of ovulation. This involved calculations with linear regression on measured values or ratios to average concentration between certain days of the mare’s cycle.
• The predictions in time of ovulation obtained through this method showed high accuracy within a range of 88 to 97%, suggesting reliability of this retrospective approach.
• However, the researchers caution that the technique may have some limitations, although these are not detailed in the abstract. These could potentially include factors such as individual differences between mares, hormonal fluctuations, or external influences not accounted for in the research.