[The value of blood progesterone determination about 18 days post ovulation for pregnancy testing in mares].

The study explores the potential of plasma progesterone levels determined around eighteen days post ovulation for identifying pregnancy in mares. The results indicate that it has a high degree of reliability, with over 78.3% accuracy for positive pregnancy diagnosis and 100% for negative diagnosis when accounting for early embryonic mortality.

Study Design

• The study involved seventy-five mares, many of which were served or inseminated across different cycles. This led to a collection of eighty-seven blood samples.
• The basis for the pregnancy assessment via progesterone levels was set at 2 ng/ml, following other research. Mares with progesterone levels above this were presumed pregnant, while those below were believed to be non-pregnant.

Results

• All twenty-five mares with progesterone levels under 2 ng/ml were confirmed not to be pregnant at the time of the examination. The progesterone levels of six samples weren’t determined, given the predictable outcomes.
• Of the sixty mares with progesterone levels higher than 2 ng/ml, forty-seven were ultimately found to be pregnant, fifty-five were likely pregnant on the eighteenth day, and five were non-pregnant and had not been pregnant.
• The study pointed out that the reliability of a negative pregnancy diagnosis based on progesterone level determination was 100% in these cases. For a positive pregnancy diagnosis, the reliability was 78.3%.
• Considering early embryonic death, the reliability of a positive pregnancy diagnosis increased to 91.6%. The overall reliability rate for the method was documented at 84.7%.

Conclusion

• This research provides substantial support for the use of plasma progesterone levels as a reliable form of pregnancy diagnosis in mares, particularly 18 days post-ovulation. In horses, a progesterone level above 2 ng/ml tends to indicate pregnancy.
• The study found that this method provides a highly reliable negative pregnancy diagnosis (100%) and a decently reliable positive pregnancy diagnosis (78.3% without, and 91.6% with, consideration of early embryonic deaths).
• Thus, the study adds credibility to the diagnostic use of progesterone levels in equine pregnancy, contributing to veterinary science and potentially impacting breeding programs.