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Selection for feed efficiency traits and correlated genetic responses in feed intake and weight gain of Nellore cattle


The objectives of this study were to estimate genetic parameters for indicator traits of feed efficiency and to recommend traits that would result in better responses to selection for increased weaning weight (W210), average daily gain (ADG) and metabolic body weight (BW0.75) and lower dry matter intake (DMI). Records of W210 from 8,004 Nellore animals born between 1978, and 2011 and postweaning performance test records from 678 males and females born between 2004 and 2011 were used. The following feed efficiency traits were evaluated: gain-to-feed ratio (G:F), partial efficiency of growth (PEG), relative growth rate (RGR), Kleiber's ratio (KR), residual feed intake (RFI), residual weight gain (RWG), and residual intake and gain (RIG). (Co)variance components were estimated by the restricted maximum likelihood method using multi-trait analysis under an animal model. Estimates of genetic gain and correlated responses were obtained considering single-stage and two-stage selection. Heritability estimates were 0.22 ± 0.03 (W210), 0.60 ± 0.08 (DMI), 0.42 ± 0.08 (ADG), 0.56 ± 0.06 (BW0.75), 0.19 ± 0.07 (G:F), 0.25 ± 0.09 (PEG), 0.19 ± 0.07 (RGR), 0.22 ± 0.07 (KR), 0.33 ± 0.10 (RFI), 0.13 ± 0.07 (RWG), and 0.19 ± 0.08 (RIG). The genetic correlations of DMI with W210 (0.64 ± 0.10), ADG (0.87 ± 0.06) and BW0.75 (0.84 ± 0.05) were high. The only efficiency traits showing favorable responses to selection for lower DMI were G:F, PEG, RFI, and RIG. However, the use of G:F, PEG or RFI as a selection criterion results in unfavorable correlated responses in some growth traits. The linear combination of RFI and RWG through RIG is the best selection criterion to obtain favorable responses in postweaning growth and feed intake of Nellore cattle in single-stage selection. Genetic gains in feed efficiency are expected even after pre-selection for W210 and subsequent feed efficiency testing of the pre-selected animals. (AU)