185 Research Article MICROBIOLOGICAL EVALUATION OF BOVINE FROZEN SEMEN SAMPLES IN WEST BENGAL, INDIA Joyjit Mitra * , Sumit Chowdhury, Santanu Panda, Mrityunjay Chakraborty, Anup Singha Received 24 September 2016, revised 16 November 2016 Assistant Director, ARD, Institute of Animal Health & Veterinary Biologicals (R & T), 37, Belgachia Road, Kolkata 700037, West Bengal, India. *Corresponding author. e-mail: joyjit.mitra@rediffmail.com. ABSTRACT: A total number of 860 French mini straws (0.25 ml) of frozen semen from 215 bulls from three different farms namely frozen semen bull station (FSBS), Harighata Farm (98), FSBS, Salboni (93) and Sperm Station, Beldanga (24) were evaluated for bacterial load by standard plate count (SPC) technique using soyabean casein digest agar and 1% plain agar media. Following incubation at 37°C for 72 hrs average colony forming unit (CFU) was estimated and bacteria were identified. Different micro-organisms identified in frozen semen samples were Staphylococcus spp., Micrococcus spp., Escherichia coli, Pseudomonas spp., Corynebacterium spp., Proteus spp., Klebsiella spp., Bacillus spp. other than Bacillus anthracis and Streptococcus spp. Several of these bacteria have been identified in association with breeding failure in cattle and warrants precautionary and preventive measures for successful breeding program. Key words: Bull, Frozen Semen, Bacteria. INTRODUCTION Artificial insemination (AI) of cows and heifers with frozen semen is widely practiced in West Bengal. The hygiene status of semen is important for vitality of spermatozoa and for the fertility of inseminated cows. Presence of bacteria, fungi and viruses has been detected in semen samples that deteriorate semen quality, as well as, transmit the pathogen to next generation. The role of specific microbes in semen leading to reproductive disorder among dairy animals is well established. Despite sanitary precautions, several ubiquitous and opportunistic microbes find their ways into semen during harvesting, processing and storage of semen (Sannat et al. 2015). A correlation was shown to exist between bacterial load and semen quality. Increase bacterial load can lead to deterioration sperm motility and viability (Shukla 2005). Addition of antibiotics to semen extenders prevents bacterial growth and may improve conception rates. The number of bacteria in semen can be decreased by keeping bulls clean and regular Explor Anim Med Res, Vol.6, Issue - 2, 2016, p. 185-191 ISSN 2277- 470X (Print), ISSN 2319-247X (Online) Website: www.animalmedicalresearch.org