SPERM-INDUCED LEUKOCYTOSIS IN THE EQUINE UTERUS

The objective of this study was to investigate the inflammatory reacti on induced in the equine uterus by insemination with fresh and frozen semen. Eleven groups (6 to 8 mares per group) were studied during 2 br eeding seasons. The mares were inseminated using raw semen, frozen sem en, extended fresh and frozen semen, concentrated fresh semen, seminal plasma and seminal extenders only. One group was bred naturally. Six hours after insemination, the uteri were flushed with 50 ml of phospha te-buffered saline (PBS). Seventeen out of 104 samples (16%) exhibited slight bacterial growth. Neutrophil concentrations were significantly (P < 0.05) higher in all treated mares than in the controls. Mares inf used with PBS, seminal extenders or the supernatant from centrifuged f rozen-thawed semen exhibited only a mild neutrophil response. Insemina tion with frozen semen resulted in higher neutrophil concentrations th an insemination with extended fresh semen (means of 59 vs 5 million ne utrophils/ml; P < 0.05). Highest neutrophil counts were found after in semination with frozen semen or concentrated fresh semen. Bacterial co ntamination of uteri was insignificant 6 hours after breeding. Neutrop hilia seems to be induced by spermatozoa rather than bacteria. The int ensity of the neutrophil reaction seems to depend on concentration and /or volume of inseminate.