Genetic parameters for feet and leg traits evaluated in different environments

The objective of this study was to test for genotype x environmental interaction (GXE) for feet and leg traits scored in different environments. Genetic correlations of seven feet and leg traits were estimated across different management systems: free versus tie stalls, slatted versus solid flooring, and intact versus trimmed hooves. Data were records from first-lactation Holstein cattle. Traits were claw uniformity, depth of heel, rear leg rear view, foot angle, bone quality, rear leg side view, and overall feet and legs. Different subsets of data were used for each comparison, resulting in 147,400; 53,550; and 145,160 records for housing, flooring, and hoof trimming management systems, respectively. Genetic parameters were estimated using REML and two-trait models in which for each animal a given trait was observed in one environment and missing in the other. Phenotypic scores were lower with tie stalls, slatted floors, and no trimming. Heritabilities tended to be greater in herds with tie stalls and slatted floors. Trimming had little effect on genetic parameters. The genetic correlations of feet and leg traits across pairs of management systems were > or = 0.85, except for rear legs, rear view. Therefore, effects of GXE were assumed to be of little importance and modification of genetic evaluation procedures on the basis of housing, flooring, and hoof conditions seems unnecessary.