Genetic parameters for hoof lesions in Canadian Holstein cows estimated from hoof trimming records

The objectives were to estimate the co(variance) components of hoof infectious and horn lesions using data collected by hoof trimmers in Canada, and the genetic correlations of hoof health traits with feet and legs conformation traits (including locomotion score) recorded by breed classifiers. Hoof health was recorded as presence or absence of specific hoof lesions in each hoof. Lesions were classified into infectious (digital and interdigital dermatitis, foot rot, and heel erosion), horn lesions (sole and toe ulcer, sole hemorrhage, and white line disease) and others lesions (interdigital hyperplasia, fissures, thin soles, and corkscrew claw). A total of 34,905 hoof health records from 27,179 cows and 365 herds, collected by 18 different hooftrimmers in Ontario, Alberta and British Columbia, were analyzed using linear animal models. In addition, 5 feet and leg conformation traits (foot angle, heel depth, bone quality, rear leg side view and rear leg rear view) and locomotion from primiparous cows were considered (n = 11,419 and 6,966 cows, for conformation traits and locomotion, respectively). At least 1 lesion was found in nearly 40% of the hoof trimming records. The heritability estimates for hoof health lesions ranged from 0.01 for front horn lesions to 0.09 for rear infectious lesions. Despite the low heritability estimates, there was a large variability in sire relative breeding value for resistance to hoof lesions. There was a positive genetic correlation between the occurrence of front and rear infectious lesions (0.77), and front and rear horn lesions (0.61), but not between infectious and horn lesions (0.08). The heritability of the conformation traits ranged from 0.04 for rear leg rear view to 0.22 for bone quality, whereas the heritability for locomotion was 0.03. The genetic correlations between the hoof health and the conformation traits were low to moderate, yet most of the estimates were associated with high SE. In conclusion, although hoof lesions are low heritable traits, there is sufficient genetic variation (as evidenced by large variability in sire relative breeding value) for genetic improvement through direct selection in the long term. Standardization of hoof health data collection should be encouraged. INTRODUCTION Maintaining hoof health is a challenge in modern dairy herds. Recent studies in North America and in Europe have reported prevalences of 40 to 70% of the cows with at least 1 hoof lesion (Manske et al., 2002; Sogstad et al., 2005; Buch et al., 2011). Hoof lesions compromise the welfare of animals (Whay et al., 2003) and can result in reduced milk yield (Warnick et al., 2001; Amory et al., 2008), reduced fertility (Hernández et al., 2001; Meléndez et al., 2003), and increased risk of premature culling (Rajala-Schultz and Gröhn, 1999; Booth et al., 2004). Many factors affect the risk of hoof lesions, including environmental factors such as the design of the facilities and management practices (Barker et al., 2009; Cook and Nordlund, 2009; Cramer et al., 2009) and genetics (van der Waaij et al., 2005; van der Linde et al., 2010; Buch et al., 2011).