Subclinical mastitis in Dutch dairy heifers in early lactation and associated risk factors

Heifer mastitis is a problem and risk factors may differ between heifers and older cows. The aim of this study was to estimate subclinical heifer mastitis (HSCM) incidence based on elevated somatic cell count (SCC) in the first 100 days in lactation and associated risk factors in Dutch dairy herds. In 2008, 173 farmers filled in a questionnaire regarding housing and herd management factors potentially related to udder health. In addition, monthly milk production and SCC data from all cattle were provided by the Dutch Royal Cattle Syndicate (CRV). On average, 25.5% (95% CI: 23.9-27.0%) of the heifers per herd had subclinical mastitis. Housing heifers together with lactating cows close to calving, was protective for HSCM compared to separate housing. In addition, farmers that removed super-numerous teats of calves had a lower HSCM incidence and day and night grazing was also protective. Herds that were milked with an automatic milking system had a higher HSCM and submitting milk samples for mastitis culturing was also associated with a higher HSCM incidence.