Evaluation of bacterial causes of subclinical mastitis in dairy cattle of Negine sabze Makoo agro-industrial and animal husbandry complex

Acute clinical mastitis resulting from udder infections and reduced resistance to pathogenic organisms is an important issue in cattle production. The aim of this study was to identify the causes of subclinical mastitis as a first step in prevention of hygienic and economic losses. Daily milk samples were collected every morning after milking and mixed with equal volume of mastitis test reagent and the mixture was rotated in a figure of 8 fashion for a few minutes. Presence of subclinical mastitis was confirmed by clotting of this mixture. The collected samples from each milking were sent to the microbiology laboratory alongside ice for bacterial culture and antibiotic susceptibility tests. Results indicated that the highest number of isolated bacteria consisted of Corynebacteria (12.54%), Staphylococcus aureus (7.92%), Streptococcus agalactiae (4.62%), Staphylococcus saprophyticus (4.62%), Staphylococcus epidermis (3.3%), Bacillus (2.64%) and Streptomyces (1.98%). Antibiotic susceptibility test revealed the greatest susceptibility to gentamicin and resistance to penicillin indicating the presence of resistance in isolated bacteria against commonly used antibiotics like penicillin, streptomycin and to some extent tetracycline but susceptibility towards the lesser used gentamicin was high.