Prevalence and risk factors associated with subclinical mastitis in lactating dairy cows under smallholder dairy farming in North East Tanzania

A cross-sectional survey was carried out between October 2016 and May 2017 to determine the prevalence of subclinical mastitis (SCM), associated bacterial pathogens and risk factors under smallholdersmall holder dairy farms in North East Tanzania. The study involved 195 cross breed dairy cows from 130 dairy farms. Data were collected based on questionnaire interview, direct observation, screening using California Mastitis Test (CMT) and culture of bacteria. The overall prevalence of SCM based on California Mastitis Test (CMT) was 70.8 and 66.4% and bacteria isolation recorded at 56.4 and 38.4% at cow and quarter levels, respectively. Prevalence defined by CMT was significantly (p<0.0001) associated with wet-dirty bedding material (OR=11.61) and poor udder (OR =6.67). Increased culture-positivity at quarter level was significantly associated with CMT-positive cows (OR= 20.59), teat injuries (OR=23.56), wooden floor (OR=2.02) and poor udder hygiene (OR =2.16). Stripping method of hand milking and first and second parity were significantly associated with lower prevalence of CMT-positive cows and culture positive quarters (p<0.05). Major bacteria species isolated included Staphylococcus aureus (55.4%), Staphylococcus epidermidis (10.8%), Escherichia coli (7.9%) and Streptococcus agalactiae (5.9%). This study demonstrated SCM is a major health constraint of dairy cattle in North Eastern Tanzania.