Abstract

A cross-sectional study was carried out to determine the prevalence of subclinical mastitis in lactating dairy cows from August 10, 2011 to May 25, 2012 in three purposively selected commercial dairy farms in Holeta district, Ethiopia. The study was carried out through field screening surveys by California mastitis test for each quarter milk sample, followed by bacteriological examination to identify the causative agents of intra-mammary infection. A total of 546 milking cows were examined, out of which 224 (41.02%) were found positive for subclinical mastitis on the basis of California mastitis test. Milk samples collected from 224 positive cows were subjected to microbiological culture for the isolation of pathogenic bacteria. One hundred eighty three (81.7%) of the samples were found positive for bacterial isolation. The major isolate pathogens wereStaphylococcus aureus (13.8%), Streptococcus uberis (12.1%), Staphylococcus epidermidis (11.7%), Escherichia coli (11.6%), Streptococcus dysagalactiae (10.6%),Pseudomonas aeruginosa (9.7%), E. coli O157:H7 (6.9%), Micrococcus species (6.5%) and Streptococcus agalactiae (6.4%) and others (10.7%). Subclinical mastitis is endemic in Holeta dairy farms and thereby necessary measures are needed to be taken to prevent further losses.

Key words: California mastitis test, bacteriological culture, prevalence, subclinical mastitis.