Incidence and occurrence time of clinical mastitis in Holstein cows

The aim of this study was to assess the incidence of clinical mastitis (CM) and its risk factors in 1725 Holstein cows. Data were collected from a private farm from 2008 to 2012. The analysis of risk factors, performed with logistic regression, showed that cows at parity 2, 3, and 4 had 65%, 88%, and 115% risk of mastitis, respectively. This risk was higher (P < 0.001) than in cows at first parity. Cows that calved from October to January had the highest (P < 0.05) risk of mastitis. The number of mastitis cases in cows at lactation 2, 3, and 4 was 18.5%, 25.9%, and 40.7%, respectively, and was higher compared to cows at first lactation. Furthermore, cows that calved from July to September showed the highest number of mastitis cases. Gamma regression parameter estimates showed that the onset time of mastitis 1 and 2 in cows that calved from October to January occurred at 16.3 and 8.5 days, respectively. This was later than cows calving from July to September. The study concluded that it is necessary to examine cows for CM during the first 2 months of lactation in order to prevent mastitis and decrease its rate of incidence.