Microbial quality of equine frozen semen

Bacteriological surveillance is little applied in management of equine frozen semen but it is quite important to verify the microbial contamination in order to find out the chance of transmission of pathology to the mare in AI. Authors describe a qualitative and quantitative analysis for bacterial contamination on long time (3–17 years) equine frozen semen stored in liquid nitrogen. The semen checked, produced in Italy and in another Europe country, was cryopreserved in liquid nitrogen inside sealed plastic straws. One hundred and ten straws were checked out for pathogenic and no pathogenic bacteria, aerobes and anaerobes and fungi (moulds and yeasts). The Total Microbial Charge was quite variable with an average of about 1.4 × 105 CFU/ml. Mostly the microbial agents identified were fungi (17.5%), Enterobacter-coccus spp. (15%), Pseudomonas spp. (6.25%), Stenothophomonas maltophila (6.25%) and anaerobic bacteria like Propionibacterium granulosum (7.5%) and Clostridium spp. (3.75%). 3.75% were unidentified Gram-negative rod and cocci. Streptococcus spp., Staph. aureus, E. coli, Th. equigenitalis and Mycoplasma spp. were not detected. The most represented species were Enterobacter-coccus spp. (1.1 × 105 CFU/ml), St. maltophila (8 × 104 CFU/ml) and Pr. granulosum (7 × 104 CFU/ml) while yeast and even more moulds were little abundant (4.7 × 104 and 3.4 × 104 CFU/ml respectively). The knowledge of equine frozen semen microbial quality is essential to check out transmission of venereal disease and improve the quality of cryopreserved germplasm.