Estudo genético do consumo alimentar residual e características produtivas e reprodutivas em um rebanho nelore

Abstract

To increase profitability in cattle breeding is important to select animals that ingest less food without compromising performance. The residual feed intake (RFI) allows the identification of animals that produce and maintains with lower consumption than expected. Were performed literature review addressing RFI as a measure of feed efficiency, and impacts of their use as selection criteria, and an article about genetic evaluation of RFI and residual feed intake adjusted for fat (RFIFat), analyzing the influence of selection for these variables on other traits. The literature review showed that selection for RFI results in herds with less demand of maintenance and consumption, however, there is disagreement about the implications on carcass traits and reproductive precocity. Are required more research, especially in zebu, to evaluate the impact of selection for RFI and indicate alternatives to their use as selection criteria. In the article it was analyzed seven tests of feed efficiency, with 946 Nellore males. It was used Bayesian Inference, animal model, in single and two-trait analysis. Dry matter intake (DMI), average daily gain (ADG), RFI, RFIFat, and metabolic weight (MBW) had moderate to high heritability, as well as rib eye area (REA), backfat thickness (BFT), rump fat thickness (RFT), marbling (MAR), subcutaneous fat thickness (SFT) and scrotal circumference adjusted to 450 days of age (SC450). Correlations of RFI and RFIFat with carcass traits were nil, except AOL, that showed genetic correlation with RFI and RFIFat of -0.42. Genetic and phenotypic correlation between RFI and SC450 were null and between RFIFat and SC450 highly positive. Selection for RFI and RFIFat resulted in a reduction of DMI (-0.31 kg /day, and -0.32 kg /day, respectively). Except REA, that showed positive indirect gain when selecting for RFI and RFIFat, correlated responses to carcass traits were nil. Indirect gain for SC450 was negative at simulated selection for RFIFat, while selecting for RFI was nil. Genetic variability observed in RFI and RFIFat demonstrates that the selection can promote genetic gains, however unfavorable genetic correlations between RFIFat and SC450 should be carefully analyzed.