Ovarian response, pregnancy rate, and incidence of multiple fetuses in mares treated with an equine pituitary extract.

The research article investigates how a pituitary extract influences ovulation, pregnancy rates, and multiple fetus incidences in mares that are not producing eggs. The findings revealed a 95% ovulation success rate using the extract, but lowered pregnancy rates, especially in cases of more than two ovulations.

Objective and Methodology

• The study aimed at studying the effect of a pituitary extract on inducing ovulation, and the subsequent impact on pregnancy rates and multiple fetus incidences in seasonally anovulatory mares – mares not releasing eggs in their cycles.
• More than half of these mares did not get pregnant despite ovulating or entered a prolonged non-breeding period before becoming anovulatory again.

Findings and Results

• The pituitary extract successfully initiated ovulation in 95% of mares when they had a follicle of 25mm or larger at the start of treatment. However, the effectiveness of the extract was not as high if the mare’s initial largest follicle was less than 25mm.
• Interestingly, the study found that ovulation occurred multiple times in 64% of the mares treated with the extract.
• In mares that had a single ovulation, the pregnancy rate was 33% – significantly lower than the 60% observed in the control group. Moreover, the pregnancy rate further decreased in mares that had more than two ovulations.

Singular Conceptus and Fetus

• In an intriguing discovery, there was a stark difference between the number of conceptuses (early stages of fetal development) perceived through palpation and the number of ovulations felt.
• Regardless of the multiple ovulations detected in the pregnant mares, only one conceptus and one fetus was found on Days 28 and 50 respectively. This was true for both the group of mares treated with the extract and the control group.