| dc.description.abstract | The study was conducted to find out the prevalence of subclinical mastitis (SCM) and its
effects on milk yield 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 are 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 42 samples were test positive out of
100, among which +(Trace) 22.0%, ++(Distinct) 12.0%, +++(Strong) 3.0%, ±(Doubtful)
5.0%. 48 samples were negative.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
samples 31 (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 infection 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. (Table 3). The 11 (11.0%) cows had mixed infection, of which 5
(5.0%) had Staphylococcus spp. + Streptococcus spp., 3 (3.0%) had E. coli + Staphylococcus
spp., and 3 (3.0%) 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%). Of the 11 mixed infections, 5 were Staph. + Strep. Among
these 5 positive samples 1 obtained from SGDF (2.86%) and 4 obtained from LFS (6.15%).
Staph. + E. coli obtained from LFS that is 3 (4.62%). Strep. + E. coli combination obtained
from 3 samples also from LFS. The overall mean milk yield of dairy cows who had bacterial
infection (SCM) reduce from 7.7 litre to 6.2 litre i.e. - 1.50 litre/cow/day. From the antibiotic
sensitivity test of sub-clinical mastitis,the result showed that ceftriaxone, ciprofloxacin and
gentamicin are the best drug for treating sub-clinical mastitis, though these antibiotics
showed maximum sensitivity to the organism responsible to cause sub-clinical mastitis. | en_US |
