The association between the endometrial biopsy grade and selected epidemiological and reproductive variables in a population of subfertile mares

Background Endometrosis, a multifactorial disease, is an important cause of subfertility in the mare, and its management is reliant on histological classification. Objectives This study aimed to determine the association between increased endometrial biopsy grade with first a mare's breed specifically either Thoroughbred or non-Thoroughbred, age and barren status and second, a clinical history indicating one or more of acute endometritis, positive bacterial culture, previous dystocia and uterine fluid retention. Study design Retrospective case series. Methods This retrospective study used historical reproductive data (2000-2015) from a population of 41 subfertile mares of various breeds, but mostly Thoroughbreds (30/41; 73%). Biopsies were interpreted by a single, experienced evaluator using the Kenney-Doig classification (1986). Results Endometrial biopsy grade was positively correlated with age (rho = 0.606; p = 0.001) but not associated with other evaluated variables (p > 0.05). Main limitations Use of a small, non-randomly selected subfertile mare population. Conclusions Mare age was an important predictor of her reproductive performance, and performing an endometrial biopsy is therefore indicated in older mares.