Susceptibility to persistent breeding-induced endometritis in the mare: relationship to endometrial biopsy score and age, and variations between seasons.

The research article focuses on the relationship between a mare’s age, endometrial biopsy score, and her susceptibility to persistent breeding-induced endometritis (PBIE). The researchers conducted two experiments to gauge these relationships and understand if the susceptibility classification is consistent over different breeding seasons.

Objective of the Study

The study aimed to achieve two main goals:

• First, to explore the associations between a mare’s age and endometrial biopsy score with uterine fluid retention after insemination.
• Second, to determine if the standard classification of susceptibility to Persistent Breeding-Induced Endometritis (PBIE) – a condition characterized by inflammation of the uterus lining following breeding – is consistent across different breeding seasons. This classification is based on the biopsy score, endometrial cytology (study of uterine cells), and fluid retention after insemination.

Overview of the Study

The study comprised two experiments:

• In the first experiment, 57 mares were inseminated with freeze-killed sperm during their estrus (period of sexual receptivity) and evaluated for uterine fluid retention 48 hours and 96 hours after insemination. The researchers examined the relationships between fluid retention and either biopsy score or age.
• In the second experiment, 14 mares from the original 57 were categorized based on their susceptibility to PBIE across two consecutive breeding seasons.

Findings of the Study

• The results indicated a strong correlation between biopsy score, age, and fluid retention. The older the mare, the higher her biopsy score tended to be, and the more uterine fluid she tended to retain post-insemination.
• The study also found that age and biopsy score were related.
• Further, it was observed that the mares’ PBIE susceptibility status might shift between seasons. Of the 14 mares re-examined in the second season, five (or 36%) showed a change in their PBIE susceptibility status. Three of these mares saw an increase in their susceptibility (from intermediate to susceptible, or resistant to intermediate). Conversely, two mares’ classification changed to a less severe PBIE susceptibility status.

Through these experiments, the study sheds light on the relationships between endometrial health, fluid retention post-breeding, and the mare’s age, while questioning the consistency of PBIE susceptibility classification across different breeding seasons.