September 2026 – Johne’s disease: The hidden impact on your herd

Johne’s disease is not always easy to see. While most people associate Johne’s disease with severe diarrhoea and weight loss in older animals, typically three to five years old, many infected herds may see less of these classic symptoms. This is often because affected animals are culled due to diminished performance, infertility, or other health issues before these symptoms become obvious. As a result, an infected herd may  still suffer from production failures that lead to premature culling.

This situation highlights that JD’s impact on herd economics and animal welfare can be much more subtle than what clinical signs alone reveal. Scientific research has linked Johne’s disease with:

• Decreased milk yield
• Premature culling, increasing replacement costs
• Lower market value of culled animals
• Elevated lameness levels
• Reduced feed conversion efficiency, leading to higher feed costs
• Compromised herd fertility
• Increased somatic cell counts in milk
• Elevated veterinary expenses and antimicrobial use

The impact becomes greater as the level of infection within a herd rises. By contrast, research indicates that financial losses are negligible in herds with a low prevalence of Johne’s disease. This makes knowing your herd’s status and acting early particularly important.

One specific area where JD causes economic loss is in milk production. An international scientific study, which included data from Ireland alongside other countries (Rasmussen et al., 2021), estimated that approximately 1% of gross milk revenue is lost annually in MAP-infected dairy herds. For individual cows, this loss translates to about €31 (around US$33) per year. These losses are primarily driven by reduced milk yield and tend to be higher in regions with above-average milk prices and production levels.

The study also compared economic losses across various countries using different assumptions, resulting in an estimated annual cost to the Irish dairy industry ranging from €11.24 million to €23.85 million. A key factor influencing these losses in all scenarios was the prevalence of JD within herds. Specifically, higher infection rates within herds significantly amplify the economic impact.

This evidence strongly supports the implementation of national JD control programs. Lowering the infection prevalence within herds can lead to substantial economic benefits across the industry, alongside improvements in animal welfare. Ultimately, proactive management and control of JD are crucial for safeguarding both the profitability and health of dairy herds.

Remember if you need any more information about the Irish Johne’s Control Programme (IJCP) please refer to the Animal Health Ireland website for further details.

Rasmussen P, Barkema HW, Mason S, Beaulieu E, Hall DC. Economic losses due to Johne’s disease (paratuberculosis) in dairy cattle. J Dairy Sci. 2021 Mar;104(3):3123-3143. doi: 10.3168/jds.2020-19381. Epub 2021 Jan 15. PMID: 33455766.