Pathological changes of the mare endometrium and genotypes for transferrin and ELA

Histological features of the endometrium, as assessed in biopsy samples, were related to Standardbred mare genotypes for transferrin, esterase (as a control) and equine leucocyte antigens (ELA). Pathological changes were found more frequently in each successively older age group of mares. Among mares aged 6-19 years, there were significant pathologic changes on first examination following an infertile breeding season for 46 of 90 (51%) of transferrin homozygotes and 50 of 146 (34%) of transferrin heterozygotes. The difference between the two groups was significant for the total data (chi 1(2) = 6.56, P = 0.010) and when the data were stratified for mare age at biopsy (chi 1(2) = 7.33, P = 0.0068). The effect of transferrin was similar in both trotters and pacers, especially for frequent genotypes commonly found in horses of both gaits. There was no effect of esterase and, in a smaller set of ELA-typed mares, no significant effect of ELA genotype on uterine biopsy category. Transferrin has a well-established microbiostatic and biocidal effect. Conceivably, heterozygotes for some combinations of transferrin variants could have a slower natural rate of endometrial deterioration than homozygotes.