Genomic prediction ability and genetic parameters for residual feed intake calculated using different approaches and their associations with growth, reproductive, and carcass traits in Nellore cattle.

This study aimed to estimate prediction ability and genetic parameters for residual feed intake (RFI) calculated using a regression equation for each test (RFI test ) and for the whole population (RFI pop ) in Nellore beef cattle. It also aimed to evaluate the correlations between RFI pop and RFI test with growth, reproductive, and carcass traits. Genotypic and phenotypic records from 8354 animals were used. An analysis of variance (ANOVA) was performed to verify the adequacy of the regression equations applied to estimate the RFI test and RFI pop . The (co)variance components were obtained using the single-step genomic best linear unbiased prediction under single and two-trait animal model analyses. The genetic and phenotypic correlations between RFI test and RFI pop with dry matter intake, frame, growth, reproduction, and carcass-related traits were evaluated. The prediction ability and bias were estimated to compare the RFI test and RFI pop genomic breeding values (GEBV). The RFI pop ANOVA showed a higher significance level (p < 0.0001) than did the RFI test for the fixed effects. The RFI pop displayed higher additive genetic variance estimated than the RFI test , although the RFI pop and RFI test displayed similar heritabilities. Overall, the RFI test showed higher residual correlations with growth, reproductive, and carcass traits, while the RFI pop displayed higher genetic correlations with such traits. The GEBV for the RFI test was slightly biased than GEBV RFI pop . The approach to calculate the RFI influenced the decomposition and estimation of variance components and genomic prediction for RFI. The application of RFI pop would be more appropriate for genetic evaluation purpose to adjust or correct for non-genetic effects and to decrease the prediction bias for RFI.