Identification of risk factors for OJD infection-level in sheep flocks.

Abstract

The level of clinical disease experienced due to ovine Johne’s disease (OJD) appears to vary considerably between infected sheep flocks in Australia, even for flocks in the same locality that appear to have similar characteristics. This has led to speculation on the cause. Risk factors for the severity of OJD were identified in this project. They were related to some farming practices such as fertiliser application, as well as to flock management and soil type. In particular weaner management and nutrition of sheep to hogget stage were important factors that producers can optimise to reduce the impact of OJD. High soil fertility, organic matter and clay content were also important factors associated with higher levels of OJD. There was less OJD associated with sandy soils. Further research is required in order to determine how these soil characteristics affect the prevalence of OJD and how best to manage soil and pasture to mitigate the losses due to OJD.