Financial modelling of the potential cost of ovine Johne's disease and the benefit of vaccinating sheep flocks in southern New South Wales

Objective To develop an enterprise gross margin (GM) model that predicts the on‐farm financial impact of ovine Johne's disease (OJD) for various sheep enterprises in Australia. In addition, to estimate the benefits and costs of control through the use of the Gudair™ vaccination, including a breakeven point. Design and population Data for the model was gained from an observational study conducted over a 3‐year period from 2002 to 2004 using sheep from 12 OJD‐infected flocks from southern New South Wales. Flocks ranged between 3500 and 20,000 sheep, with owner estimates of 5% or greater OJD mortality at the start of the study. Procedure A GM model was developed to predict the on‐farm financial impact of OJD for various sheep enterprises in Australia, comparing non‐infected, infected (status quo) and infected (vaccination) disease scenarios. Results Vaccination breakeven points are achieved within 2 to 3 years for breeding enterprises if OJD mortalities are high, rising towards 7 years for a Merino ewe enterprise if OJD mortalities are low. Conclusion The GM model demonstrates the returns to investment of vaccination for Australian sheep producers with OJD‐infected flocks.