Genetic relationships between claw health traits of dairy cows in different parities, lactation stages, and herds with different claw disorder frequencies.

Claw disorders affect cow welfare and profitability of farms. Not only claw disorders but also the need for trimming, known as trimming status, has been shown to be heritable. Limited knowledge is available on whether claw health traits (claw disorders and trimming status) are genetically the same trait in different parities, lactation stages, or in herds with low or high frequency of claw disorders. The aim of the current study was to estimate frequencies, heritabilities, and genetic correlations of claw health traits measured in different parities (first vs. later parities), in different lactation stages (early vs. late lactation), and in herds with different frequencies of claw disorders (low vs. high frequency). Analyses revealed that heritabilities measured in different parities, lactation stages, or herds with different trait frequencies are similar for most claw health traits. Also, genetic correlations (rg) for most claw health traits were not found to be different from unity for traits in different parities, lactation stages, or herds with different trait frequencies. Sole hemorrhage and infectious lesions were genetically different traits in first or later parities (rg=0.29±0.31 and 0.66±0.15, respectively). White line separation and infectious lesions were genetically different in early and late lactation (rg=0.53±0.20 and 0.69±0.13, respectively), and sole ulcer was genetically different in herds with low or high frequency of sole ulcer (rg=0.75±0.14). In our analysis, we did not find convincing evidence to supports the use of multiple trait models for the analysis of claw health traits treating them as different traits in different parities, lactation stages, and herds with different claw disorder frequency.