Fatty acid profile of duodenal digesta and of meat of feedlot beef cattle fed diets containing different levels of concentrate

The objective of this study was to evaluate the fatty acid profile of duodenal digesta (experiment I) and of meat of beef cattle (experiment II) fed diets containing different levels of concentrate (220, 400, 590 and 790 g of concentrate/kg of dry matter of the diets). The experiment I was conducted with four Charolais-Nellore steers (460 +/- 18.2 kg of BW), with a T-shaped duodenal cannula, using a double 4 x 4 Latin square as an experimental design. In experiment II, 16 crossbred Charolais-Nellore young bulls (192.44 +/- 18.2 kg of BW) were randomly distributed in the experimental treatments (220, 400, 590 and 790 g of concentrate/kg of dry matter of the diets). The diets were isonitrogenous (120 g of crude protein/kg of dry matter). The intramuscular fat content was used as a covariant for the statistical analysis of the meat fatty acid profile. The duodenal content of fatty acid C17:0 decreased with increase of concentrate levels, while its content in the meat presented a quadratic variation with the increase of the concentrate levels of the diets, being the lowest values observed for the diet with 400 g of concentrate. The duodenal content of fatty acid C18:1 trans-11 decreased, whereas the content of this fatty acid in the meat increased with the increase of the dietary concentrate levels. The increase in the level of concentrate reduced the content of polyunsaturated fatty acids C18:3 n-3, C20:3 n-6, C20:4 n-6, and C20:5 n-3 EPA in both the duodenal digesta and meat. No difference was observed in the n-6/n-3 fatty acids ratio (mean of 13.96) of the meat between diets. The elevation of the level of concentrate in confinement diets reduces the nutraceutical quality of the meat of Charolais-Nellore young bulls slaughtered at 14-16 months of age due to the reduction of the polyunsaturated fatty acids content important for human health.