A method for estimating the economic value of changes in the risk of breech strike

Abstract

An economic model of the costs of sheep flystrike has been modified to examine the effect of a given change in the risk of breech strike as if it applied to the entire wool-producing industry, rather than to individual wool producers. Within each region (high rainfall, sheep/cereal and pastoral zones), the model sets the proportion of the sheep population in low, medium and high risk categories and calculates the estimated level of strike for untreated sheep in those groups. The costs related to breech strike can be calculated according to the original model. The risk of breech strike can then be adjusted to any required level, the proportion of sheep in each category adjusted and the costs recalculated according to the adjusted risk. The model estimated that a 50% reduction in the risk of breech strike would decrease the number of sheep requiring preventive treatment to about one-third of previous levels, but only provide a small reduction in costs related to struck sheep, due to the large increase in the number of sheep no longer receiving preventive treatment. There would be only small reductions in costs related to crutching and mulesing sheep unless much larger reductions in strike risk occurred. The overall benefit of a 50% reduction in the risk of strike would be $0.23–0.27 per sheep. If this reduction in strike risk occurred across all regions this could provide a benefit to the Australian sheep industry of $15 million. The model found that if mulesing was not used in any of the sheep then the use of preventive treatment would increase so that 93% rather than only 60% received chemical treatment, and reduction of the risk of breech strike by 50% provided benefits of $0.40 per sheep. Therefore, the estimated benefits would be greater than $0.27 per sheep in situations where the current level of risk is very high.