[Value of adding antibiotics to frozen bovine semen: the example of mycoplasmas and campylobacters].

Two studies have been conducted to control opportunistic pathogen bacteria in frozen bovine semen. The first one was reported by Shin et al. (1988) and was based on (a) an experimental in vitro contamination of raw bull semen with various types of bacteria, (b) adding several antibiotics, alone or in combination with different concentrations. The second experiment, performed in our laboratory, was designed to compare from 240 split ejaculates the effect of adding concentrated solutions of antibiotics to the raw semen vs control (ie addition of antibiotics in the extender). The combination of gentamicin (500 micrograms/ml)-tylosin (100 micrograms/ml)-linco-spectin (300/600 micrograms/ml) was found to be the most effective on the strains of bacteria tested. The addition of a concentrated solution of antibiotics to the raw semen was not found here to be of any advantage on the numbers of CFU. Furthermore, such a protocol contributed to significantly decrease the percentage of motile spermatozoa. In conclusion, opportunistic pathogens such as those here studied may be kept under control with the appropriate antibiotics and with no deleterious effect on semen parameters provided that they are added at the adequate concentrations in the diluents used for semen cryopreservation.