Presence of bacteria on the external genitalia of healthy stallions and its transmission to the mare at the time of breeding by live cover

The current field study used thoroughbred stallions and mares from central Kentucky to investigate the occurrence of potentially pathogenic bacteria on the stallion's external genitalia, based on cultures, and investigated the occurrence of bacteria and type of isolate in the mare's uterus after breeding by live cover to stallions with or without positive bacterial cultures. Fifteen thoroughbred stallions and 206 mares from two central Kentucky thoroughbred farms were used during the 2010 and 2011 breeding seasons. Samples for bacteriological evaluation were taken from the prepuce and postejaculate urethra (n = 201) of stallions. Uterine swabs (n = 264) were collected 12-18 hours postbreeding. For statistical analyses, a chi-squared test was used to test the relationship between stallion culture results and postbreeding uterine culture results, as well as the effect of bacterial types found on the stallion cultures with bacterial types found on the postbreeding uterine cultures. Of stallion cultures, 22.4% were positive for potentially pathogenic bacteria, with Streptococcus equi subspecies zooepidemicus (51.1%) being the most common isolate. Uterine cultures resulted in a 29.2% positive rate for potentially pathogenic bacteria, with S. equi subsp. zooepidemicus (90.9%) being the most common. There was no difference (P > .05) in the occurrence of bacteria or type of isolate found on uterine cultures after breeding stallions with or without positive cultures. In conclusion, potentially pathogenic bacteria found on the stallion's external genitalia did not affect the occurrence and type of bacterial isolate found in the mare's uterus after breeding by live cover.