Post breeding uterine cytology
Keywords: equine, insemination, breeding, neutrophils
It is normal for mares to experience an influx of neutrophils into the uterus shortly after breeding. This occurs after natural breeding or artificial insemination and is already obvious within six hours after it has occurred. As reviewed by Katila A. Chapter 104 in Equine Reproduction. 2011 Ed. McKinnon et al. ISBN 978-0- 8138- 1971-6, the neutrophil influx has largely disappeared by 48 hours after breeding. Also, the majority on spermatozoa have been eliminated by four hours after insemination. In that respect therefore, the cytology from this mare is unusual because at 72 hours post breeding there are still large numbers of neutrophils in her cytology and some spermatozoa are clearly visible.
This was not unexpected in this case because this 10 year old mare had been pooling fluid in her uterus for some time. This indicated that physical aspects (myometrial contraction and expulsion of uterine contaminants) of her uterine defense mechanism had been compromised; a common problem in older mares. Eight days after breeding, fluid was still present in the uterus but only cell debris remained. No bacteria were present. Incidentally, there had been no plan to breed this mare; a stallion escaped from his stall and this mare let herself out of her stall!
Interestingly, it appears to be the presence of spermatozoa themselves that have the greatest chemotactic influence on the influx of neutrophils (through the activation of complement). Semen plasma is also important, but less so.
