Prevalence of Clinical and Sub-clinical Mastitis in Lactating Dairy Cows at the National Jersey Breeding Centre, Samtse, Bhutan

Abstract

This study investigated the prevalence and risk factors of clinical mastitis (CM) and sub-clinical mastitis (SCM) in lactating dairy cows through clinical examination and California Mastitis Test (CMT). Bacterial culture and drug sensitivity test was conducted to investigate the causal agents of mastitis and drug resistance on dairy cows. Fifty six milk samples were collected from October, 2014 to March, 2015. Prevalence of CM and SCM detected by both CMT and culture was 5.4% and 78.6% respectively. The prevalence of CM was higher in adult cows (18.2%), jersey breed (9.7%), cows with moderate parity (11.8%), high milk yielder (8%), and at late lactation stage (12.5%). The SCM
infection varied among age groups showing increased infection with advancement of age. Higher infection with SCM was seen in Karan Fries breed (80%) than Jersey breed (77.4%). The SCM prevalence tended to increase with increased parity and milk yield. The infectious bacteria isolated were Staphylococcus aureus, Pasteurella multocida and Escherichia coli with prevalence of 89.4%, 8.5%
and 2.1% respectively. S. aureus isolates were sensitive to most antibiotics tested except penicillin. P. multocida was susceptible (100%) to Gentamycin and resistant (100%) to Cloxacillin and Penicillin. E. coli showed susceptibility to both Gentamycin and Tetracycline, but was resistant to Amoxicillin, Cloxacillin, and Penicillin. The study indicates that there is high prevalence of SCM on the farm, which could be controlled by use of Gentamycin and Tetracycline.