Boar semen bacterial contamination in Italy and antibiotic efficacy in a modified extender

The aims of the study were to identify microbial flora in boar semen under field condition in Italy. Investigate about antibiotic resistance and sensitivity of isolated bacteria and postulate the efficacy of antibiotics (amikacin vs gentamicin) as a component of semen extender. A total of 60 boars were collected in 13 pig farms. Bacteriological and mycological investigations were performed immediately on raw semen samples and then on semen diluted randomly in a new short-term modified extender (ME-S) and in a commercial one (CRONOSTM) after 48 and 120 hours. Bacterial contamination were found in 63% of raw semen samples and were isolated E.coli, Serratia marcescens, Staphylococcus epidermidis and aureus, Proteus spp., Streptococcus spp. and Pseudomonas aeruginosa. E. coli was the most contaminant isolated (53%). Pseudomonas aeruginosa, was found only in one semen sample. The analysis of variance of factors affecting contamination levels were significant for the farmof origin (P<0.05) and not significant for the breed. Antibiotic resistance of these bacteria was assessed using different antibiotics. Significant differences (P<0.05) between observed and expected frequencies of bacterial isolates resistant or not to the antibiotics contained in the extenders were found. At 48 hours of storage a reduction of aerobic contamination were found after ME-S dilution by 85.3% and after CRONOSTM by 63.8%. This paper proved the presence of pathogenic bacteria in semen, so we believe that it is highly advisable to perform a periodical microbiological screening of boar semen in swine industry to avoid the use of low sperm quality.