The Addition of Lactobacillus spp., Enrofloxacin or Doxycycline Negatively Affects the Viability of Mycoplasma bovis in Diluted Bovine Semen

SIMPLE SUMMARY: Mycoplasma bovis is an important infectious agent in cattle. The pathogen may cause a wide range of clinical signs, including mastitis, arthritis, pneumonia and reproductive disorders. Artificial insemination with contaminated semen may be a source of infection in infection-free areas or herds. Hence, the antimicrobials used in the preparation of seminal doses should be re-evaluated, or alternative measures to antimicrobials should be tested. This in vitro study aims to evaluate novel strategies to reduce the risk of the transmission of the pathogen through contaminated semen during artificial insemination. Hence, we assess the effect of the addition of (1) the antimicrobial enrofloxacin, (2) the antimicrobial doxycycline, or (3) a probiotic of human origin that contains acid lactic bacteria of the genus Lactobacillus, on the viability of Mycoplasma bovis in diluted bull semen in a Tris-citrate-fructose medium. The data show that the pathogen is negatively affected by the addition of 0.125 μg/mL of enrofloxacin, 0.0625 μg/mL of doxycycline, or the probiotic at a concentration of 3.24 × 10(6) or 3.24 × 10(8) colony-forming units/mL in diluted semen. Our results are promising in the field, as they may support new strategies to reduce the risk of the transmission of Mycoplasma bovis through artificial insemination. ABSTRACT: Mycoplasma bovis is an important etiologic agent of bovine mycoplasmosis in cattle. Different transmission routes have been described, including those related to reproduction. The presence of mycoplasma in semen has led to its appearance in infection-free areas through artificial insemination (AI). Semen was recently reported to be the initial source of two M. bovis mastitis outbreaks in two closed dairy herds in Finland. This questions the effectiveness of the antimicrobials currently used in semen extenders to control the pathogens in contaminated semen. They should be re-evaluated, or alternative measures to antimicrobials should be tested to obtain M. bovis-free semen. This in vitro study aimed to assess different strategies to reduce the risk of transmission of M. bovis through AI technologies. The viability of M. bovis (PG45, NCTC 10131) in bull semen diluted (DS) in a Tris-citrate-fructose solution was tested, after the addition of enrofloxacin, doxycycline or a Lactobacillus spp.-based probiotic. The data show the susceptibility of the pathogen to the addition of 0.125 μg/mL of enrofloxacin or 0.0625 μg/mL of doxycycline and to the addition of the probiotic at a concentration of 3.24 × 10(6) colony forming units (CFU)/mL or 3.24 × 10(8) CFU/mL in DS. The Tris-citrate-fructose medium negatively affected the viability of M. bovis, although this effect was lower than that observed after the addition of the probiotic and antimicrobials (p < 0.05). Our results may support new strategies for reducing the risk of M. bovis transmission through AI.