Intrauterine fluid accumulation in oestrous mares.

Intrauterine fluid (IUF) was collected using a tampon from mid-oestrous mares (n = 57) with and without ultrasonically detectable accumulations of free intraluminal fluid. Bacteria were cultured and neutrophils counted from all samples (n = 57). Total protein concentration, trypsin-inhibitor capacity (TIC), and plasmin, beta-glucuronidase (B-Gase) and N-acetyl-beta-D-glucosaminidase (NAGase) activities were determined in 27 IUF samples. The motility of spermatozoa in the presence of IUF, IUF extended with Kenney's medium (1:1) and Kenney's medium alone was analysed in 9 samples using a Hamilton-Thorn motility analyser. Thirty-five mares were inseminated immediately after collection of IUF, and every second day until ovulation. Embryos were recovered nonsurgically 6 days after ovulation. After embryo transfer, fluid accumulations were recorded during oestrus and an endometrial biopsy specimen taken (n = 53). In the beginning of oestrus, fluid accumulations were detected in 39% (22/57) of mares, while on the day when IUF was collected, fluid accumulations were observed in 26% (15/57) of mares. The fluid was anechogenic, and in 80% of the mares located in the uterine body. None of the mares exhibited cytological or bacteriological evidence of acute endometritis. Total protein concentrations, TIC and B-Gase activities in IUF were statistically significantly lower in mares with fluid accumulations (n = 14) than in mares without fluid accumulations (n = 13) (p < 0.01). The addition of undiluted IUF to extended semen significantly reduced total and progressive motilities, path velocities and percentages of rapid spermatozoa (p < 0.05) in vitro. On endometrial biopsy, fibrosis was found to be more prominent (p = 0.025) in mares with fluid accumulations (n = 9) than in mares without (n = 44). It was concluded that anechogenic fluid accumulations during oestrus were associated with compositional changes in IUF. Although IUF had negative effects on spermatozoal motility in vitro, the presence of fluid accumulations at the time of insemination did not affect embryo recovery rates.