Microbial load in frozen bull semen and antibiogram of the isolates

Abstract

The mean bacterial load in the frozen semen procured from the three frozen semen production centres viz., Mannuthy (Centre A), Dhoni (Centre B) and Mattupatti (Centre C) were 2260 + 880.65, 825.91 + 186.06 and 80.33 + 18.47 respectively. The mean bacterial load per dose of semen differed significantly between these three centres. The mean fungal load of semen in Centre A and B were significantly greater than that produced in Centre C. The mean coliform counts, pseudomonad count, staphylococci and micrococci count and mycoplasma count were detected in specific media. Mycoplasma sp. were not detected in Centre A while four out of eleven samples from Centre B and two out of fifteen samples from centre C contained Mycoplasma. The total bacterial load of all the samples from Centre A exceeded the ISI specification of 500 organisms per insemination dose of semen while 72.7 per cent of the samples from Centre B exceeded this limit. None of the samples from Centre C exceeded 500 organisms per dose of semen. The mean bacterial load per dose of semen from bulls below four years of age was significantly higher than those from bulls between the age group of four and six years. The mean bacterial and fungal load per dose of semen from crossbred Holstein Friesians were significantly greater than those of crossbred Jerseys. The bacterial isolates from the semen from these centres where characterised. They belonged to the species, Bacillus licheniformis, B. alvei, B. cereus, B. brevis, Corynebacterium bovis, C. pseudodiphtheriticum, C. hofmanii, Staphylococcus ayreus, S. epidermidis, Aerococcus viridans, Micrococcus varians, Kurthia sp. Flavabacterium sp., Alcaligenes faecalis, Pseudomonas alcaligeness, PS. Mendocina, Levine asp., Enterobacter aerogeness, Enterobacter liquifascians, Edwardsiella tarda, Citrobacter koseri, C. intermedius, C. freundii, Providencia rettgeri, Escherichia coli. The fungal isolates from sêmen, which were characterised belonged to the species Candida albicans, C. pseudotropicalis, C. tropicalis and C. krusei. The filamentous fungi isolated were Aspergillus niger, A. fumigatus, Penicillum sp. and Microporum gypseum. Of the 20 antibiotics studied for the sensitivity pattern, pefloxacin, doxycycline, chloramphenicol, ciprofloxacin and norfloxacin were found to be sensitive to majority of isolates. Among the antifungal agents studied, nystatin followed by clotrimazole were sensitive to more than 80 per cent of the fungal isolates. Nystatin may be used in semen extender for checking the fungal contaminants in frozen semen. The study recommends and addition of the new antibiotics to semen extenders after further field studies.