Magnitude and variation of clinical mastitis and its associated costs in dairy herds of Argentina

A survey was conducted to evaluate the magnitude and variation of clinical mastitis among dairy herds. Prevalence, cumulative incidence and incidence rate were estimated, exploring risk factors at cow level and economic consequences. A cross sectional convenience sample of 2,535 Holstein-Friesian milking cows from 19 herds was the study population. Herd prevalence was estimated the day of the visit. Cows that showed no clinical signs were followed during 15 days to get incidence estimates. Mixed logistic models and survival analysis were applied. Using prevalence data, each case was monetized considering milk discharged, treatment costs and estimated milk losses until dry-off. Overall gross prevalence was 2.5 cases/100 cows (95% CI = 1.9-3.1), cumulative incidence was 3.9 new cases/100 mincing cows (95% CI = 3.1-4.7) and incidence rate was 2.7 new cases/1.000 cow-days (95% CI = 2.2-3.3). The herds medians were 1.69 (q1 = 0, q3 = 4.2), 3.6 (q1 = 2.0, q3 = 4.6) and 0.25 (q1 = 0.14, q3 = 0.42), respectively. Cows during early lactation showed higher odds of being a prevalent case (OR = 1.69; 95% CI = 1.01-2.85). In cows, cumulative incidence (OR = 3.36; 95% CI = 1.84-6.11) and incidence rate (HR = 3.83; 95% CI = 2.05-7.15) were three times higher compared with heifers, after the adjustment for days in milk and herd. Average cost for case was US$ 185.01 and US$ 143.03 in cows and heifers, respectively, and the average losses reached up to US$ 4.50/milking cow (95% CI = 3.38-5.61). This is the first study documenting the clinical mastitis frequency and losses in dairy herds of Argentina.