Implementation of genomic evaluation for digital dermatitis in Canada

Abstract

Digital dermatitis represents the most prevalent hoof lesion in Canada, with almost 20% of cows affected. A data collection system of hoof lesions, which uses standardized and reliable scores, was developed in Canada within a four-year project started in 2014. Hoof trimmers willing to share data and to develop a standard protocol were identified across Canada. Consecutively, a pipeline for a routine flow of hoof lesion records from hoof trimmers to Canadian DHI and to Canadian Dairy Network (CDN) was developed. The data collected through this pipeline were then used to develop a herd management report provided by DHI, and a national genomic evaluation for digital dermatitis offered by CDN. The genomic evaluation was introduced in December 2017, using hoof lesions recorded by hoof trimmers between 2006 and 2017. Heritability and repeatability estimates for digital dermatitis were 0.08 and 0.20, respectively. Breeding values were estimated for Holstein cattle with a univariate linear animal model. Other possible indicator traits for digital dermatitis, such as selected conformation traits, were not included due to low genetic correlations, and low contribution to increase in prediction reliability. Single-step genomic evaluation was implemented using a reference population of 19,459 animals (5,268 sires and 14,191 cows, respectively). The average reliability for bulls in the reference population was 77%. Correlations between GEBV for resistance to digital dermatitis and traits currently under selection were all favorable.