Antibiotic-resistance in Veterinary andrology

The requirement for stringent standards to assure the biosecurity of insemination doses is increased by global commerce in frozen semen because the semen used in artificial insemination (AI) must be free of infectious organisms. Although the high standard of hygienic handling, collected bovine semen contains variable amounts of bacteria derived from non-sterile materials and the urinary tract microbiota. It was estimated that bacterial contaminations were estimated in 50% of the frozen insemination doses. Furthermore, the storage temperature of the insemination doses (-196°C) maintains viable bacteria. To control bacterial growth, different combinations of antimicrobials are added to extenders for semen cryopreservation. Nowadays, the use of a combination of gentamicin-tylosin-lincomycin-spectinomycin (GLTS) is largely recommended, as reported by the criteria included in the Directives of the European Union and European Council (EEC directives ex 88/407, 90/429 and 92/65, now in force the Reg. EU 2016/429). On the other hand, several episodes of antimicrobial resistance are increasingly described in domestic animals (Santos & Silva, 2020). In the present study, the effectiveness of the commercial extenders to control bacterial contamination in bovine semen was assessed and the protective effect of different antimicrobial combinations, containing ceftiofur/tylosin and ofloxacin have been tested. The results suggested that the new combinations of antimicrobials are more effective than conventional to control bacterial growth in bovine cryopreserved semen. Alternatives to antibiotics, including peptides, physical methods, and the use of various substances of plant origin are proposed, but studies are required to elucidate their effectiveness in bacterial control, thus actually antimicrobials in the bovine semen extenders are unavoidable to guarantee a high-quality standard of the insemination doses.