Prevalence and Associated Factors of Bovine Mastitis on Small Holder Dairy Farms in and Around Arsi Negele, West Arsi Zone, Oromia Region, Ethiopia

A cross-sectional study was conducted from December 2018 to April 2019 on 384 selected dairy cows in Arsi Negele, Oromia Region, Ethiopia. The objectives of the current study were to determine the prevalence of mastitis and identify associated risk factors in smallholder dairy farms. The study animals were selected using a combination of simple random sampling and purposive type of sampling techniques. Information on farm management practices and potential risk factors was obtained through informal interview and on site discussion with owners of dairy farm during farm visit. The California Mastitis Test (CMT) was used for mastitis screening, and data were analyzed using SPSS version 20. Out of the 384 milk samples tested by CMT test, 184 of them were positive for mastitis with an overall prevalence of 47.9% and of this, 42.7% and 5.7% were subclinical and clinical mastitis, respectively. The risk factors were found significantly associated with mastitis positivity. At the quarters level, out of 1536 quarters examined, 232 (15.1%) were positive for mastitis. The study has indicated that adult and old age cows were 2.33 and 2 times more likely at risk (P < 0.05) in contracting mastitis as compared to young cows, respectively. The study has also highlighted that cows in the late stage lactation were 3.86 times more likely to contract mastitis relative to early stage lactation cows. By undertaking bacteria culture and isolation 50% positive milk samples, the three most important bacterial isolates detected were: Staphylococcus aureus, Streptococcus genus and Escherichia coli with respective proportion of 50%, 33% and 17%. The current study indicated a concerning prevalence in small holder dairy farms revealing concerning health constraints of dairy cows in the study area.