Estimation of Breeding Values for Footrot in New Zealand Merino Sheep

Footrot affects all aspects of sheep production and has substantial welfare and economic impacts, particularly for the fine-wool industry in New Zealand (NZ), which is largely dominated by Merino sheep and high rainfall environments. Genetic selection provides an opportunity to improve resistance to footrot and in turn reduce the production loss and management costs associated with footrot outbreaks. Footrot was recorded on 2,196 yearling wethers in a Central Progeny Test (CPT) environment with a further 1,081 phenotypes available for industry animals. The heritability of average footrot score was 0.20 ± 0.05 in the CPT. However, ultimately the successful provision of industry breeding values for footrot will rely on a larger pool of phenotypes across environments and genotypes. The inclusion of phenotypes scored in five industry flocks, linked to the CPT via pedigree, led to a small decline in variances and heritability for average footrot score, relative to CPT data. Transitioning phenotypes based on the biological progression of footrot resulted in similar residual variance estimates when industry data was included, indicating breeding values are likely to be more comparable across challenge events. We propose that incorporating industry phenotypes will provide breeders with greater capacity to obtain estimates of the genetic potential of young animals to resist footrot.