Genetic correlations of hoof lesions and trimming status with feet and leg conformation traits in Canadian Holsteins

Abstract Text: The objectives of this study were to estimate genetic correlations between hoof lesions and feet and legs conformation traits and to evaluate the association between those latter traits and the pre-selection process that leads a cow to be presented or not to the hoof trimmer. Hoof lesions were recorded by 23 hoof trimmers in 365 Canadian herds from 2009 to 2012. Hoof lesions included in the analysis were digital dermatitis, interdigital dermatitis, interdigital hyperplasia, sole hemorrhage, sole ulcer, toe ulcer, and white line lesion. Hoof lesions recorded during the first parity and hoof lesions recorded in second or later parities were considered as different traits. Conformation traits considered were bone quality (BQ), foot angle (FA), heel depth, rear leg side view, rear leg rear view (RLRV), locomotion (LOC) and the overall score for feet and legs (FL). In total, 37,158 cows that had a trim record in first and/or later parities also had conformation traits records. A second series of analyses considered all cows that were in a given herd during the trimming period, including cows that did not have any hoof data during the lactation. An additional trait, the trimming status, was defined as follows; a value of 1 was assigned to cows that had been visited at least once by the trimmer during the lactation, and a value of 0 to cows that did not have a hoof trim recorded during the lactation but were in the herd during the trimming session. Approximately 30% of cows were not presented to the trimmers during the lactation. Digital dermatitis, interdigital dermatitis and interdigital hyperplasia detected in first and later parities were negatively correlated to RLRV, FL, and LOC, with genetic correlations ranging from -0.24±0.11 to -0.62±0.15. With the exception of white line lesions, all of the horn lesions recorded in parities ≥ 2 showed moderate positive correlations with FA (from 0.29±0.12 to 0.55±0.20). White line lesions detected in parity 1 showed moderate genetic correlation with RLRV (0.65±0.19), FL (0.53 ±0.18), and LOC (0.44±0.21), and those detected in parities ≥ 2 were correlated to BQ (-0.27±0.10) and LOC (0.37±0.16). The trimming status had moderate negative correlations with LOC and FL, suggesting that the pre-selection process for which cows are presented to the hoof trimmer is not random, but rather is associated with mobility and the conformation of the cow.

Keywords: Hoof lesions; conformation traits; trimming status