Johne’s disease, caused by the bacterium Mycobacterium avium subspecies paratuberculosis, is a chronic infectious disease common in the dairy industry with significant economic and animal health impacts. Losses occur primarily due to reduced milk production, premature culling, decreased fertility, and compromised immune function. Despite decades of research and control efforts, progress has been slowed by the largely subclinical nature of the disease, long incubation period, and limitations in diagnostic testing. The objectives of this thesis were twofold: first, to assess whether low production during early lactation could be a practical predictor of Johne’s disease test status and help determine culling strategies; and second, to explore farmers' perceptions of Johne’s disease, including the barriers and motivations that affect their adoption of control measures. To achieve these objectives, a participatory study was conducted on eight Vermont dairy farms to examine how providing targeted information—specifically, Johne’s disease test status, the economic value of the cow, and milk production—impacts producers' culling decisions. Farmers’ decision-making processes were observed to understand how the provision of this information ultimately informed culling decisions. A focus group with participating farmers further explored the concerns and challenges producers face when adopting management changes. Findings indicate that low production in early lactation is not a reliable predictor of Johne’s disease test positivity. While economic considerations influenced culling decisions, they were not the only factor, as producers also considered disease risk, herd management goals, and financial constraints. This work highlights that, although Johne’s disease remains a concern on dairy farms in Vermont, existing management practices and financial limitations influence farmers’ decision-making processes.
Whitney Hull (Wed,) studied this question.