[Effect of antibiotics on the microflora of bull sperm and its fertilizing capacity]

The effect was tested under laboratory in vitro conditions of eight antibiotics in media for thawing pelleted bull semen. It was found that the addition of antibiotics during the process of reanimation had no unfavourable impact on the motility of spermatozoa. Upon storage in water bath (39 degrees C) in the course of six hours gentamycin, amoxicillin, kanamycin, and polymixin preserved the semen cells and enhanced their survival rate at the same level as that of the control medium with no antibiotic. The combination of penicillin and streptomycin lowered 2.5 times spermatozoal motility. Worst was the survival rate of spermatozoa when the medium was supplemented with oxytetracycline and chloramphenicol. It was also found that best sanitation qualities with regard to the microflora in semen had gentamycin, which, at that did not produce any negative effect on the rate of survival. The conception rate of cows inseminated with semen treated with gentamycin at thawing was shown to be 15.3 per cent higher, and when treated with the combination of penicillin and streptomycin it was 3.0 per cent higher at first insemination than that of the control group of animals inseminated with semen with no antibiotic supplement.