predicted on the basis of requirements for maintenance, milk production and body weight change, is a measure of feed effeciency. Genetic parameters of residual energy intake, and its correlations with feed intake and yield traits were investigated, using 3503 monthly records of 906 Holstein lactating cows in three herds. Different requirements of energy were estimated using models from NRC. Genetic parameters were estimated through multivariate analysis by derivative free approach of restricted maximum likelihood algorithm, fitting an animal model with fixed effects of herd-year-season, parity number and stage of lactation, as well as random effects of animal additive genetic, permanent environment and residuals. The estimated heritability of residual energy intake was 0.21 ± 0.02. Results indicated that selection against residual energy intake might moderately improve feed efficiency. Moreover, residual energy intake could be combined with other traits in a selection index for improving both yield and feed efficiency.
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