Effect of dietary fat concentration from condensed corn distillers’ solubles, during the growing phase, on beef cattle performance, carcass traits, digestibility, and ruminal metabolism

The objectives of this study were to determine the effect of fat concentration from corn distillers’ solubles (CDS), fed during the growing phase, on DMI, gain, carcass traits, digestibility, ruminal metabolism, and methane emissions of steers. In Exp. 1, 40 steers (age = 136 ± 20 d; BW = 185 ± 11 kg) were randomly allotted to 1 of 5 dietary treatments: 1) a cornbased growing diet (CNT), 2) 0% CDS, 3) 10% CDS, 4) 19% CDS, or 5) 27% CDS. Diets 2 through 5 included coproducts (corn gluten feed and soybean hulls) and were formulated to achieve fat concentrations of 3, 5, 7, and 9%, respectively. Diets were fed once daily for 106 d (growing phase). All steers were fed a corn-based diet from d 107 to 196. Contrasts were used to examine 1) the difference between CNT and 10% CDS and 2) linear and quadratic effects of CDS inclusion. During the growing phase, steers fed CNT had increased (P < 0.01) ADG and G:F compared with steers fed 10% CDS. Increasing CDS inclusion increased (linear, P ≤ 0.02) ADG and G:F. Overall, steers fed CNT had increased (P < 0.01) ADG compared with steers fed 10% CDS, but increasing CDS inclusion had no effect (P = 0.19) on overall ADG. Overall DMI and G:F were not different (P ≥ 0.16) in any contrast. There was a trend (Linear; P = 0.08) for ultrasound marbling at d 196 to increase as CDS inclusion increased; however, there were no effects (P ≥ 0.20) of treatment on carcass marbling or quality grade. In Exp. 2, 5 steers (BW = 335 ± 56 kg) were fed Exp. 1 diets for ad libitum intakes in a 5 × 5 Latin square design. Apparent DM digestibility increased (linear, P = 0.02) with increasing dietary CDS inclusion. Steers fed CNT had greater (P = 0.01) DM digestibility than those fed 10% CDS. Fat digestibility increased (linear, P < 0.01) in steers with increasing CDS, but NDF and ADF digestibility were not affected (P ≥ 0.17) by treatment. Similarly, ruminal pH and VFA concentrations were not affected (P ≥ 0.13). Also, there was no difference (P ≥ 0.37) in ruminal methane emissions (g/h). In conclusion, feeding corn during the growing phase increased overall ADG compared with 10% CDS coproduct-based diet but did not affect carcass traits or methane production. Increasing dietary fat inclusion from CDS in coproductbased diets linearly increased DM and fat digestibility and predicted marbling scores via ultrasound but did not affect marbling at slaughter, NDF digestibility, propionate, or methane production.