The Use of Antibiotics in Cryopreservation of Ram Sperm

Antibiotics are used in extenders for sperm cryopreservation, however no specific regulation has been established for ram sperm. This study evaluates the effects of antibiotics in ram sperm extenders for bacterial control and its effect on sperm viability. Sperm from five rams was collected, cooled and frozen using extenders with the following antibiotics: 100,000 IU/mL penicillin and 100 μg/mL streptomycin (PES); 500 μg/mL gentamycin, 100 μg/mL tylosin, 300 μg/mL lincomycin and 600 μg/mL spectinomycin (GTLS); 50 μg/mL ceftiofur sodium (CEF); and 1,000 μg/mL enrofloxacin (ENR). Bacillus sp., Corynebacterium sp., Klebsiella sp. and Staphylococcus sp. were isolated from fresh sperm and perpetual area. For cooled sperm, the antibiotic PES, GTLS and ENR were able to reduce the number of colony forming units per mL (CFU/mL), however, CEF was inefficient in all tested concentrations. Motility of cooled sperm was reduced when GTLS and ENR were used (P < 0.05). For thawed sperm, the number of CFU/mL was similar across all treatments (P > 0.05), however, motility was reduced with ENR treatment at doses greater than 50% (P < 0.05). The antibiogram revealed resistance of Staphylococcus sp. and Klebsiella sp. to the penicillin/streptomycin association and to tylosin. Both PES and GTLS were able to control bacterial growth on cooled sperm. However, attention should be given to the antibiotics added to the extenders, which may impair sperm motility.