STUDY ON BOVINE SUB-CLINICAL MASTITIS ON FARM CONDITION WITH SPECIAL EMPHASIS ON ANTIBIOGRAM OF THE CAUSATIVE BACTERIA
The study was conducted to find out the prevalence of sub-clinical mastitis (SCM) and antibiogram of the causative bacteria in dairy cows at the Sylhet govt. Dairy Farm (SGDF) and Local Farms of Sylhet (LFS) during the period of July2014 to June2015. These farms were selected to assess the predominant types of bacteria involved in causing sub-clinical mastitis and to know the in vitro antibiotic sensitivity spectrum of these bacterial isolates against the commonly used antibiotics and to study the economic effects due to SCM. Use of California Mastitis Test (CMT) for the detection of sub-clinical mastitis showed 42out of 100 samples were test positive, among which +(Trace) 22.0%, ++(Distinct) 12.0%, +++(Strong) 3.0%, ±(Doubtful) 5.0%. Bacteriological examination of milk samples of 100 milch cows (400 quarters) revealed that 42 cows (42.0%) had suffering from SCM with different bacterial infection with 95% confidence limit was 32.1574-51.8426. Among 42 positive samples31 (31.0%) cows had mono-bacterial infection and 11 (11.0%) cows had mixed bacterial infections. Statistical analysis of the result of single and mixed bacterial infections in the milk of apparently healthy milch cows revealed that the single infection was significantly (P < 0.05) higher than mixed bacterial infection. Of the 31 mono-bacterial isolates, of which 23 (23.0%) isolates were Staphylococci, 3 (3.0%) isolates were Escherichia coli, 5 (5.0%) isolated Streptococcus spp. The 11 cows had mixed infection, of which 5 had Staphylococcus spp. + Streptococcus spp., 3 had E. coli + Staphylococcus spp., and 3 had Streptococcus spp. + E. coli. Of 42 positive cases of SCM Staphylococcus spp. isolated from 23 samples. Among these 23 positive samples 13 obtained from SGDF (37.14%) and 10 obtained from LFS (15.38%). Escherichia coli isolated from 3 samples. Among these 3 positive samples 3 obtained from LFS (4.62%). Streptococcus spp. isolated from 5 samples. Among these 5 positive samples 1 obtained from SGDF (2.86%) and 4 obtained from LFS (6.15%). Ceftriaxone, ciprofloxacin and gentamicin were the best drug for treating sub-clinical mastitis.