Overview of the Current Problem

Over the past 2 years, there have been an increasing number of farms in North America identified which experienced increased normal returns to estrus, presence of post-mating vaginal discharges, and/or decreased sperm longevity in extended porcine semen. With further investigation, we found that sperm clumping and sperm cell death were occurring in the extended semen product within 1-2 days of semen collection/processing. In most situations, sperm clumping was visible to the naked eye when agitating extended doses of semen in their packaged container. Negligible sperm motility was present in samples which exhibited sperm clumping. With further analysis of the clumped semen samples, we found that we could isolate bacteria from these doses of semen. All bacteria isolated from these contaminated, extended porcine semen samples were found to be resistent to gentamicin, an antibiotic preservative added to most commercially available porcine semen extenders. These bacteria were further tested in our laboratory and subsequently found to kill extended porcine sperm through both direct and indirect mechanisms of action.

A visit was made to several of these farms in an attempt to identify where the source(s) of bacterial contamination existed. Observations were first made at the farm on their methods of semen collection, semen processing and semen storage. Cultures were then taken form laboratory equipment, disposable and non-disposable supplies, powdered/reconstituted extenders, boars and the boar stud environment. From these field investigations, procedural weaknesses were identified as potential sources of contamination. Confirmation as sources of contamination was then made through the isolation and comparison of the source bacteria with the bacteria identified in the extended semen samples. All bacteria originated from the farm environment, and were found to be of animal and non-animal origin. A protocol was developed which would minimize the potential for contamination of the semen product at the boar stud. These minimum contamination techniques (Table 1) were applied to boar preparation, semen collection, semen processing and laboratory sanitation. After implementation of these techniques on the problem farms, no further recurrence of the problem has occurred at any of the farms.