A cross-sectional study was conducted from October 2010 to May 2011 to estimate the prevalence of mastitis, isolate and characterize major bacterial pathogens and to assess the association of some putative risk factors with occurrence of mastitis in cows in smallholder dairy farms in Shashemene, southern Ethiopia. A total of 245 lactating cows (111 Holstein, 98 Holstein-local Zebu crosses and 36 indigenous Zebus) were examined clinically and California Mastitis Test (CMT) was used to detect clinical and subclinical mastitis. The overall prevalence of mastitis at cow and quarter level was 37.1% (91/245) and 30.0% (288/960), respectively. Seventy (28.6%) cows were with subclinical mastitis while only 20 (8.6%) had clinical mastitis. The prevalence of mastitis significantly (P<0.05) differed with breed, parity, stage of lactation and previous record of mastitis. A total of 217 bacterial isolates were recovered from 288 mastitic milk samples and Gram-positive cocci were the most common pathogens. The pathogens isolated were Staphylococcus aureus(28.1%), other Staphylococcus species (22.1%), Streptococcus agalactiae (10.1%) other Streptococcusspecies (14.3%), coliforms (22.1% that is Escherichia coli, 10.6%; Klebsiella species 7.8% andEnterobacter species 3.7%), Micrococcus species (1.4%), Pseudomonas species (1.4%) and Bacillusspecies (0.5%). Therefore, culling of older cows with repeated mastitis records and dry cow therapy will be practiced to reduce the risk of mastitis. Culling of old and chronically affected cows, screening for mastitis, awareness creation among smallholder farmers about the importance of sub-clinical mastitis and milking and barn hygiene should be considered in reducing the effect of mastitis.
Key words: Bacterial isolates, California Mastitis Test, mastitis prevalence, risk factors, Shashemene.
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