Effect of artificial insemination site on post-mating endometritis in mares

Aim of the study was to determine the effect of artificial insemination (AI) location on post-mating endometrial inflammation 1 and 6 days after AI. Six mares with ages ranging from 12 to 23 years were inseminated with a same batch of frozen semen for 3 consecutive cycles. Mares were inseminated with the following procedures in a random order: (1) Deep uterine insemination with 4ml of semen; (2) Horn bifurcation with 4ml of semen; (3) Horn bifurcation with 4ml of semen and 6ml of extender. During each cycle, Cotton (C) and Brush (B) swabs were collected at 4 different moments: mid- dioestrus, mares with a 35mm follicle, 24h and 6 days after AI. Swabs were smeared on slides, fixed and stained (Diff-Quick®) before examination under light microscopy. Proportions of inflammatory and epithelial cells were determined and differences were studied with kruskal-wallis test for non-parametric data. Distensions of uterine lumen due to intraluminal fluid observed during ultrasound exams were measured and recorded. Quality of slides was better (p=0.0006) with B swabs than C swabs with 97% versus 65% of slides readable. B swabs were associated with higher percent of endometrial cells retrieved (p=0.0323), making them a better tool for endometritis diagnosis, which is consistent with our previous reports. Volume of intraluminal fluid and percent of inflammatory cells, both on B and C swabs, were not influenced by AI location regardless the timing of sampling. Small volume deep uterine AI did not significantly affect inflammatory response by the endometrium in our experiment.