RVC Study Finds Early Johne’s Disease Marker in Calves

Researchers at the Royal Veterinary College (RVC) have shown that antibodies against Johne’s disease can be detected in the blood of newborn dairy calves after they have received colostrum from their mothers, potentially unlocking a new pathway to earlier detection of exposure. Reported on 27 July 2026, the small-scale UK study opens the door to using existing routine calf blood samples for Johne’s disease screening rather than waiting for adult testing.

The team analysed blood samples from 38 newborn dairy calves and their dams at a commercial dairy farm in south-west England, using serum residuals originally collected for routine monitoring of colostrum antibody absorption. They measured MAP-specific antibodies (against Mycobacterium avium subspecies paratuberculosis, the causative agent of Johne’s disease) and applied statistical modelling to relate the results to maternal Johne’s status and to colostrum antibody transfer efficiency. Calves born to cows carrying MAP antibodies showed higher levels of MAP-specific antibodies themselves, and the relationship between antibody levels and colostrum absorption differed depending on maternal MAP status.

Jonathan Hedgecock, RVC veterinary student graduate and lead author, framed the practical implication as significant: many calves are already blood sampled at a young age for serum total protein testing, so extending testing to Johne’s would require no additional sample collection. Johne’s disease, a chronic and incurable wasting disease that causes major losses to dairy herds through reduced milk yield, culling and welfare impact, has traditionally been difficult to diagnose given its long incubation period and the limited sensitivity of adult tests. The study is small in scale (38 calves, one farm), but points to a straightforward routine-workflow route to earlier surveillance.

The commercial signal is an emerging opportunity in the dairy diagnostics market, where new low-friction routes to early Johne’s surveillance could reshape herd testing strategies. If the finding replicates at scale, existing calf serum total protein workflows become a natural add-on channel. Expect IDEXX, Zoetis, MSD Animal Health and Thermo Fisher to watch closely.

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