Understanding the diagnostic tests and challenges in host genetic selection against Johne’s disease in New Zealand dairy cattle

Canonically, this is described in terms of susceptibility, resistance and resilience. However, within field studies, it is very difficult to identify animals with these characteristics. For example, the combination of repeated and combined diagnostic testing, together with longitudinal production data required to identify resilient animals, can be very expensive. This review shows that more NZ-based research is required around strategies that optimise the use and value of what are inevitably imperfect diagnostic tests. Such work should be undertaken alongside a focus on identifying the genetic differences behind the JD phenotypes.