Characterization of the risk of deer-cattle interactions in Minnesota by use of an on-farm environmental assessment tool.

OBJECTIVE To characterize the risk of interactions that may lead to the transmission of Mycobacterium bovis between cattle and white-tailed deer (Odocoileus virginianus) on farms in northern Minnesota. SAMPLE 53 cattle farms in northwestern Minnesota adjacent to an area where bovine tuberculosis-infected cattle and deer were detected. PROCEDURES A semiquantitative deer-cattle interaction assessment tool was used for the 53 cattle herds. Farm risk scores were analyzed on the basis of deer damage to stored feed. RESULTS 27 (51%) farms reported deer damage to stored cattle feeds within the year previous to the farm visit. A strong association was found between increases in the percentage of land that could serve as deer cover and deer damage to stored feeds on a farm. The total risk score was significantly associated with the probability of a farm having deer damage. By use of a logistic regression model, the total risk score and proportion of nonagricultural land around a farm could be used to predict the likelihood of deer damage to stored feeds. CONCLUSIONS AND CLINICAL RELEVANCE Management practices on many farms in northwestern Minnesota allowed potential deer-cattle interactions. The on-farm risk assessment tool served as a valuable tool for prioritizing the biosecurity risks for farms. Continued development of biosecurity is needed to prevent potential transmission of bovine tuberculosis between deer and cattle, especially on farms that have a higher risk of deer damage.