Can we breed for resistance to buffalo flies?

Buffalo flies (BF) (Haematobia irritans exigua) are major pests in the northern Australian cattle industries causing production loss and welfare impacts. Control of BF currently relies mainly on chemical treatments and the use of tropically adapted breeds. There is good evidence that resistance to BF and closely related horn flies (HF) is heritable and improvement within breeds should be possible with a suitable selection strategy. However, heritability estimates have varied considerably for both BF (0.06–0.36; McKinnon et al. 1990; Burrow 2001) and HF (0.10–0.59; Brown et al. 1992; Fraga et al. 2004) and there have been few practical attempts to incorporate BF resistance into cattle selection programs. This variability is likely largely due to the difficulty of accurately phenotyping cattle for BF resistance because of the propensity of BF to redistribute among cattle when disturbed. In the longer term the use of biomarkers or genomic indices for resistance, which do not require direct exposure to BF for selection to occur, present the most practically attractive means of selecting for BF resistance. However, the identification of suitable indirect criteria will depend on accurate and practically feasible direct phenotyping methods. In this study we compared the accuracy of methods based on visual counting and photography, used together with image analysis, to estimate BF resistance.