Substitution of the protein source in the concentrate for corn co-product at Nellore young bulls in the finishing phase on feedlot

The aim of this study was to evaluate the effects of DDGS (dry distiller grain with soluble), as a protein source substitute in conventional concentrate, on such as dry matter intake (DMI), daily weight gain (DWG) and carcass yield. The research was conducted at the forage experimental facilities of Animal Science Department at FCAV/UNESP, Jaboticabal, S?o Paulo, Brazil. Forty-two Nellore young bulls with initial average body weight (BW) 453 ? 47 kg were housed in individual pen (16m?) on feedlot. Diets were formulated with 30% of roughage (corn silage) and 70% of concentrate. Animals were fed twice day and orts adjusted to 10% of dry matter provided. The experimental diets were: conventional supplement (SUP) (cottonseed meal, corn grain, mineral urea and monensin) or supplement with DDGS replacing 100% of protein source (SUP100). The concentrate was formulated with 17.8% of crude protein (CP), estimated to 1.5 kg of DWG and 2.3% BW to DMI. Animals were submitted to 21 days as an adaptation period and later fed for 84 days to evaluate the DMI, DWG and carcass yield. The DWG was obtained by weighing the animals at beginning and in the end of the experiment, and divided by experimental days (84 d), always considering a previous 14-h solid and water fasting. The DMI (offered feed minus orts) and the carcass yield were obtained after the animal slaughter and related to the final BW. Data were evaluated in a PROC MIXED of SAS with a randomly design. The means of least squares were compared (P < 0.05) by Tukey test. The DMI was 1.83 and 2.21% of BW to the treatment SUP and SUP100, respectively, and the difference between both treatments was 13.7% (P<0.005). The increase of DMI resulted in a DWG variation of 31.2% when comparing the treatments SUP and SUP100 (0.808 and 1.175 kg of DWG to the treatments SUP and SUP100, respectively). There was no difference (P=0.2985) in carcass yield between treatments (57.1 and 57.7 % of carcass yield to the treatments SUP and SUP100). It is possible to conclude that diet with DDGS increased the total DMI, improved the animal performance, however the carcass yield were not affected by performance difference.