Bovine mastitis: Prevalence, causes and associated risk factors in Silte Zone, Ethiopia

Mastitis is an important disease of dairy cows, and it causes huge economic losses to dairy farm owners due to a decrease in milk  production, and reduction in milk quality, and an increase in the cost of cow treatment. A crosssectional study was conducted in Southern  Ethiopia’s Silte zone from October 2020 to June 2021 aimed to estimate mastitis prevalence, assess related risk factors, and  identify prevalent bacterial causes. Three hundred eighty-four lactating cows were examined for abnormalities in udder quarters and  teats. Milk samples were tested for subclinical mastitis via the California mastitis test (CMT) and cultured for causative agents from  clinical mastitic and CMT-positive cows. The overall prevalence of mastitis was 54.9% (95% CI=49.9-59.9), of which 52.1% (95%  CI=47.1-57.1) was subclinical and 2.9% (95% CI=1.6 -5.1) clinical mastitis. From a total of 1536 quarters examined 41 (2.7%) quarters were  found blind and 427 (27.7%) quarters were affected by mastitis. Overall, more hind quarters, 236 (55.5%) were affected than the front  quarters, 189 (44.5%) of udder. The prevalence of mastitis was significantly higher during early lactation, ≤4 months (p< 0.05); and it was  increased with increasing parity (p< 0.05) and age (p< 0.05). Cows with no bedding were more affected than those with bedding (p< 0.05).  Multivariable logistic regression showed that cows with round and flat teat ends were 2.84 and 11.85 times more likely to contract  mastitis. Also, cows with pendulous udder, producing more than 10 liters per day milk and during the early 4 months of lactation were  1.87, 6.81, and 2.14 more likely affected by mastitis than normal udder, producing less than 10 liters of milk per day and lactation after  five months, respectively. Milk samples collected from 211 mastitis-positive cows were cultured using standard bacteriological technique,  and the isolated bacteria were Staphylococcus aureus (29.5%), Staphylococcus epidermidis (14.2%), Staphylococcus intermedius (11.6%),  Staphylococcus hyicus (11.1%), Streptococcus agalactiae (8.9%), Streptococcus disgalactiae (6.3%), E. coli (5.8%), Streptococcus uberis(5.3%), Klebsiella spp. (1.6%) and Enterococcus spp. (1.1%). Owners should givepro per udder care and are advised to apply dry cow therapy. Extension workers should raise awareness.