RESUMO
Inactivation of leptospires in pools of semen from three Holstein Friesian bulls, collected in an artificial vagina, was investigated. Spermatic concentration was adjusted in egg yolk citrate extender, submitted to the following treatments: A (control; without antibiotics); B (penicillin, 1,000 UI/mL - streptomycin, 1,000 icg/mL); C (amoxicillin, 1,000 icg/mL); D (ceptiofur sodium, 1,000 icg/mL); E (amoxicillin 1,000 icg/mL - ceptiofur sodium 1,000 icg/mL). Leptospires (2.0 x 10(6) leptospires/mL) were added into the diluted semen. Recovery of leptospires was obtained in modified EMJH semi-solid medium with and without antibiotics. The antibiotics in the concentrations used did not affect means of percentage of progressive motility and individual progressive motility of spermatozoids. Penicillin-streptomycin presented the best results in leptospire inactivation (97.1 percent). Amoxicillin, ceptiofur sodium and their combination at the concentrations studied presented poor results: 59.29 percent; 32.5 percent and 60.36 percent of inactivation, being less effective in leptospire inactivation than penicillin-streptomycin.