Subclinical mastitis and associated risk factors on dairy farms in New South Wales.

OBJECTIVE To determine the current prevalence of subclinical mastitis (SCM) and associated risk factors on dairy farms in New South Wales. METHODOLOGY A survey was sent to 382 dairy farmers to acquire information on the relevant risk factors associated with SCM. RESULTS The average herd prevalence of SCM among the 189 respondents (response rate 49.5%) was 29%. Farmers who had herds with a low prevalence (<20% cows with individual somatic cell count (ISCC) >2 × 10⁵ cells/mL) more frequently wore gloves during milking (26% vs 62%), used individual paper towels for udder preparation (16% vs 62%), fed cows directly after milking (47% vs 87%) and more frequently treated cows with high ISCC (69% vs 80%) than farmers who had herds with a high prevalence of SCM (>30% cows with ISCC >2 × 10⁵ cells/mL). The latter more often used selective dry cow therapy (52% vs 24%), compared with low prevalence herds. CONCLUSION The prevalence of SCM in this cross-sectional study is comparable or lower than reported in other studies from North America and the European Union. The outcome provides a benchmark for the current focus of the NSW dairy industry on the management practices associated with a low prevalence of SCM, such as wearing gloves, using paper towels and feeding cows directly after milking.