Prevalence of clinical and sub-clinical mastitis on cross bred dairy cows at Holleta Agricultural Research Center, Central Ethiopia

A study on bovine mastitis, designed to determine the prevalence and causal agent in cross breed dairy cow, was conducted from November, 2009 to March, 2010 at Holleta agricultural research center. A total of 90 cross bred cows were examined by physical examination and California mastitis test (CMT). Out of the total animals examined, 81.1% (73) had mastitis, in which 7.8% (7) and 73.3% (66) had clinical and sub clinical mastitis, respectively. Out of 340 quarters examined, 80.88% (275) were found to be infected in which 5.59% (19) were clinically and 75.3% (256) were sub clinically. Of 275 CMT and physically positive animals, quarter samples were taken for microbiological test in which, 66.4% (180) were culturally positive and 33.09% (91) were negative. Of 180 positive samples, the majority of isolates were Staphylococcus aureus (43.3%), followed by Micrococcus spp. (17.2%), Streptococcus agalactiae (12.2%), and Streptococcus dysgalactiae (7.2%). In addition, lowest isolation rate was for Streptococcus uberis and Streptococcus feacalis and each accounts for 2.8%. From this, proper mastitis control should be practiced by maintenance of an appropriate cow's environment and udder health management program in the farm including further investigation on risk factors associated to prevalence of mastitis and antibiotic resistance test to undertake measurable control options of mastitis in the farm. Key words: Cross bred, dairy cow, causal agent, holleta, mastitis, prevalence.