Authors: POUYA ZAMANI, SEIED REZA MIRAEI ASHTIANI, HOSEIN MOHAMMADI
Abstract: Residual energy intake (REI) or residual feed intake (RFI), defined as the difference between actual energy intake, is predicted on the basis of requirements for maintenance, milk production, and body weight change of an animal. Genetic variation of REI and its relationships with dry matter intake, milk yield, fat corrected milk yield and milk fat, and protein yields was investigated using 3503 monthly records collected from 906 Holstein lactating cows. Variance components were estimated using univariate and multivariate animal models with the derivative-free approach of restricted maximum likelihood algorithm, fitting animal models with fixed effects of herd-year-season, parity number and stage of lactation, and random effects of animal additive genetic and permanent environment. The estimated heritability and repeatability for REI were 0.15 and 0.53 from univariate, and 0.21 and 0.60 from multivariate models, respectively. REI had a genetically weak and negative correlation with yield traits (from -0.05 to -0.08) and a positive correlation with dry matter intake (0.61). Moderate heritability estimate for REI, along with negligible genetic correlations with yield traits and high genetic correlation with dry matter intake, might reveal that selection against REI improves feed efficiency by reducing feed intake and increasing yield traits a little.
Keywords: Residual energy intake, residual feed intake, genetic parameters, dairy cattle
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