Onset and Duration of Uterine Inflammatory Response of Mares after Insemination with Fresh Semen

The onset and duration of the inflammatory response after insemination (AI) were studied in eight mares. The mares were inseminated during estrus with fresh semen containing 600 million spermatozoa. Uterine fluid was absorbed into a tampon 0.5, 1, 2, 4, 8, 12, 24, and 48 h after AI. Only one sample per mare was taken during a given estrous period. All mares were examined by rectal palpation and ultrasonography before AI and before sampling. Bacteria were cultured from semen and uterine fluid by means of a 48-h incubation on blood agar. Spermatozoa and neutrophils were counted from the fluid by a Bürker chamber. Spermatozoa—the majority with heads and tails detached—were present in high but steadily decreasing numbers from 0.5 to 4 h and had completely disappeared at 48 h after AI. Corynebacteria, which were cultured from all ejaculates, were cultured in all mares at 1 h and in most mares at 0.5 and 2 h after AI. The first neutrophils appeared as early as 0.5 h after AI. The numbers of neutrophils increased steadily, reaching their highest levels at 8 h after AI. High levels persisted until 24 h and had disappeared at 48 h after AI. The values at 4, 8, 12, and 24 h were significantly different from those at other sampling points. Clinical signs of inflammation (discharge, increase in endometrial edema) were evident from 4 to 24 h after AI.