Genetic analyses of hoof lesions in Canadian Holsteins using an alternative contemporary group
Keywords:hoof lesions, dairy
A key goal of dairy herds is to reduce the incidence of hoof lesions, which can be achieved both by improving management practices, and through genetic selection. Previous research has shown that data collected by hoof trimmers can be used for genetic evaluation of hoof health. Generally, not all cows in the herd are trimmed during the lactation and the pre-selection process for which cows are presented or not to the hoof trimmer needs to be considered. The objective of this study was to estimate genetic parameters for individual hoof lesions in Canadian Holsteins using an alternative contemporary group, in order to consider all cows in the herd during the period of the hoof trimming sessions, also those that were not examined by the trimmer over the entire lactation. Data were recorded by 26 hoof trimmers serving 365 herds located in Alberta, British Columbia and Ontario, and trained to use a rugged touch-screen computerized lesion recording system. A total of 108,032 hoof trimming sessions from 53,654 cows were collected between 2009 and 2012. Hoof lesions included in the analysis were digital dermatitis, interdigital dermatitis, interdigital hyperplasia, sole hemorrhage, sole ulcer, toe ulcer, and white line lesion. All variables were analyzed as binary traits, as the presence or the absence of the lesions. At first, only cows that were examined by the hoof trimmers were analyzed. Heritabilities (SE) for digital dermatitis, interdigital dermatitis, interdigital hyperplasia, sole hemorrhage, sole ulcer, toe ulcer, and white line lesion were 0.067 (0.007), 0.015 (0.003), 0.036 (0.005), 0.017 (0.003), 0.038 (0.006), 0.006 (0.002), and 0.017 (0.002), respectively. In a second step, cows without a record but present in the herd during the period of the hoof trimming sessions were included in the analyses, and a “no-lesions” label was assigned to all hoof traits for that trimming session. Heritabilities (SE) for digital dermatitis, interdigital dermatitis, interdigital hyperplasia, sole hemorrhage, sole ulcer, toe ulcer, and white line lesion were 0.053 (0.005), 0.011 (0.002), 0.025 (0.004), 0.012 (0.002), 0.031 (0.004), 0.004 (0.001), and 0.012 (0.002), respectively. Despite the low heritability, differences between daughter groups were observed based on the best and worst breeding values of the sires in both the groups. The pre-selection process, which leads cows to be trimmed or not during the lactation, did not affect the heritability and the breeding values estimation.
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