The period of the follicular phase during which the uterus of mares shows estrus-like echotexture influences the subsequent pregnancy rate.

This research explores the influence of the duration of estrus-like echotexture within the follicular phase of mares’ uteruses on their subsequent pregnancy rates. The study included both spontaneous and prostaglandin-induced cycles, finding that the pregnancy rate increased with the extended duration of estrus and endometrial edema.

Objective of the Research

• The primary focus of this study was to understand how the length of the estrus-like echotexture period during the follicular phase in mares, could affect their subsequent pregnancy rates (PRs). This was investigated in both spontaneous cycles and those induced by prostaglandin (PGF).

Methods Employed

• A total of 768 estrous cycles from 325 thoroughbred mares were incorporated for data analysis in this study.
• Among them, 401 estrous cycles were induced using exogenous PGF, while the remaining 367 cycles remained untreated.
• To discern the impact on PRs, the study considered relevant factors such as the age of the mare, stallion, breeding year, season month, reproductive status of the mare, use of PGF treatment, duration of the follicular phase demonstrating estrus-like echotexture, the interovulatory interval (IOI) in spontaneous cycles, and the interval from PGF treatment to ovulation (ITO) in PGF-induced cycles.

Research Findings

• The study found that the following factors significantly influenced the PR: mare’s age, mare’s status, ITO, and the duration of the follicular phase with estrus-like echotexture.
• Extended periods of estrus and endometrial edema, demonstrated in both PGF-induced and spontaneous estrous cycles, associated with increased PRs.
• Positive correlation was observed between the duration of endometrial edema and both IOI and ITO, with their interrelationship being statistically significant.