Post-breeding endometritis after low dose insemination in the mare

Abstract

Hysteroscopic insemination in mares with delayed uterine clearance (DUC mares) is controversial. While some authors proposed that insemination with a reduced volume and number of spermatozoa may reduce post-mating endometritis, others proposed that the hysteroscopic procedure is inflammatory and should not be used in DUC mares. The overall objectives of this study were to evaluate the incidence and severity of post-mating endometritis in reproductively normal and DUC mares after hysteroscopic insemination at the uterotubal junction, and to determine if hysteroscopic insemination could be used in DUC mares to reduce post-mating endometritis. The mares were classified as normal or DUC based on the presence of intrauterine fluid 24 or 48 hours after a semen challenge. In Experiment 1, the acute endometritis was evaluated 24 hours after insemination. Each mare (n=5 normal, n=5 DUC) received three treatments in three consecutive estrous cycles: UB: uterine body insemination (one billion spermatozoa, 20 mL), HYST: hysteroscopic insemination (five million spermatozoa, 0.5 mL) and SHAM: sham hysteroscopic insemination (semen extender, 0.5 mL). Intrauterine fluid accumulation and uterine leukocyte numbers were not influenced by treatment. In the second experiment, residual endometritis was assessed 48 hours after insemination, and the effect of insemination method on fertility was evaluated. Each mare (n=4 normal, n=5 DUC) received four treatments in four consecutive estrous cycles: UB: uterine body insemination (one billion spermatozoa, 20 mL), HYST: hysteroscopic insemination (five million spermatozoa, 0.5 mL), SHAM: sham hysteroscopic insemination (semen extender, 0.5 mL) and SP: hysteroscopic infusion of seminal plasma (0.5 mL). There was no difference in intrauterine fluid accumulation between treatments in normal mares. HYST and SHAM treatments resulted in more fluid accumulation 24 hours after the procedures in DUC mares than UB and SP. However, leukocyte numbers were not different. It was concluded that the hysteroscopic procedure itself is inflammatory, so it should not be used with the intention of reducing post-mating endometritis. However, the inflammation was not greater than that induced by routine uterine body insemination and fertility was not affected. Therefore, there is no contraindication to its use in mares with delayed uterine clearance.