Factors associated with being a bovine-virus diarrhoea (BVD) seropositive dairy herd in the More and Romsdal County of Norway

Factors associated with being a bovine-virus diarrhoea (BVD) seropositive d airy herd were studied in a case-control study of 314 dairy herds in the Mo re and Romsdal County of Norway, Information was collected through a mailed questionnaire, and associations were modeled using conditional logistic re gression after selecting variables by a best-subset procedure. Purchasing o f animals, use of common pasture, herd-to-herd contact over pasture fences, purchasing cattle with insufficient health (about BVD) documentation, and not using dairy advisors were associated with higher risk. In addition, you nger farmers were more likely to have a bovine-virus diarrhoea seropositive herd than older farmers. 'Other animal traffic', including use of common a nimal housing in the summer months and exchange of calves between farmers w ere also risk factors, Collectively, these factors could explain 51% of the seropositive herds. (C) 1999 Elsevier Science B.V. All rights reserved.