Antibiotic control of Campylobacter fetus by three extenders of bovine semen.

Campylobacter fetus were added to raw semen in two factorial experiments that evaluated seminal extender, initial antibiotic treatment of raw semen, and inclusion of antibiotics in the extender. Extenders were conventional egg yolk citrate, complete egg yolk Tes-Tris, and complete egg yolk Tris. Raw semen was treated with 2000 micrograms streptomycin sulfate and 1000 units of polymyxin B sulfate per milliliter. Antibiotic-treated extender contained 500 units of polymyxin B sulfate, 1000 micrograms streptomycin sulfate, and 500 units of potassium penicillin G per milliliter. Aliquots of extended semen were cultured immediately prior to freezing in .5-ml French straws and after thawing. Treatment of raw semen or extender alone with antibiotics was not consistently effective in controlling Campylobacter fetus. The dual treatment of raw semen and incorporation of antibiotics into the extender were effective with egg yolk citrate and egg yolk Tes-Tris. However, Campylobacter fetus survived in semen that had been treated with antibiotics and then extended with egg yolk Tris containing Antibiotics. Thus, the procedure required by Certified Semen Services for antibiotic treatment of bovine semen was ineffective in controlling Campylobacter fetus in semen extended in this complete egg yolk Tris. Efficacy should be demonstrated, rather than assumed, for each procedure for extending and processing bovine semen.