Toni is a Vetlife Mid Canterbury
production animal veterinarian.
Johne’s disease remains one of the most significant and costly diseases affecting New Zealand dairy herds. While DairyNZ estimates the national cost at $44–80 million annually, the real question is: what is it costing your own business?
The challenge is that many of the losses caused by Johne’s disease are hidden. Clinical cases are often only the tip of the iceberg, with the greatest economic impact coming from infected cows that appear healthy but are already affecting herd performance.
The hidden costs commonly include:
• Reduced milk production
• Premature culling and increased replacement costs
• Reduced cull cow value
• Poor feed conversion efficiency
• Increased veterinary costs and treatments
• Reduced genetic gain through the loss of productive animals.
Unlike diseases such as BVD, Johne’s disease is not something that can be eliminated in a single season. The bacteria (Mycobacterium avium subspecies paratuberculosis, or MAP) has a long incubation period, meaning animals are often infected for several years before showing clinical signs. As a result, successful management requires a long-term commitment rather than a short-term solution.
Before beginning any testing programme, the most important question is “What are we trying to achieve?”
Every farm has different priorities. Your goal may be to reduce clinical cow losses around calving, protect young stock from infection, reduce the number of high-risk cows remaining in the herd, or simply to gain a better understanding of the level of infection within the herd. Defining these objectives from the outset allows the testing programme to be designed around your business rather than applying a one-size-fits-all approach.
It is equally important to understand what Johne’s testing can – and cannot – tell us.
Testing is an invaluable management tool, but it is not a cure, and it will not eliminate Johne’s disease on its own. Likewise, a single negative test does not guarantee an animal will remain negative for life. As the disease progresses over several years, infected animals may not produce detectable antibodies until much later, meaning repeated testing over time is required to monitor infection status.
Fortunately, there are several testing options available, each with different strengths depending on your objectives. These may include herd-level milk testing through herd test samples, whole-herd blood testing, targeted testing of high-risk cows, or blood testing replacement heifers before calving. The most effective programme is one that aligns with your farm goals and can adapt as those goals change over time.
Perhaps the most important ingredient for success is the relationship between the farming team and their veterinarian. Johne’s disease management is a journey that requires realistic expectations, regular review and a willingness to adjust the plan as new information becomes available. There is no single test or treatment that will solve the problem overnight, but with a well-planned, long-term strategy, significant improvements can be made.
If you are unsure what Johne’s disease may be costing your business, or would like to understand the options available for your herd, talk to your veterinarian. Together, you can develop a practical management programme that fits your farm, your goals and your future.
Key takeaway:
Johne’s disease is one of the most costly production diseases affecting New Zealand dairy herds, with many losses hidden in apparently healthy cows through reduced milk production, premature culling, poorer feed efficiency and lost genetic progress. Because Johne’s disease develops slowly and cannot be solved with a single test or treatment, effective control starts with clear farm goals, repeated testing and a long-term management plan developed with your veterinarian.
