Inclusion of dry or wet fiber plus solubles or high protein distillers grains to replace flint corn, whole cottonseed, and soybean meal in diets for finishing Nellore bulls

The objective was to evaluate the inclusion of three corn ethanol byproducts in finishing cattle diets: high protein distillers grain (HPDG) was used as a source of protein in the diet to entirely replace whole cottonseed and soybean meal, dry fiber plus solubles (DFS) and wet fiber plus solubles (WFS) were used as energy-protein sources in the diet to replace a portion of the corn and entirely replace whole cottonseed and soybean meal from the conventional diet. Diets were formulated to be isonitrogenous with all diets containing 15% corn silage, 12% soybean hulls, 0.55 to 0.85% urea, and 1.80% mineral and vitamin supplements on dry matter (DM) basis. The treatments were (% DM): 1) control (CON): 8% whole cottonseed, 5% soybean meal, and 57.6% ground corn; 2) HPDG: 10.3% HPDG and 60.35% ground corn; 3) DFS: 30% DFS and 40.35% ground corn; 4) WFS: 30% WFS and 40.35% ground corn. Pre-planned contrasts included CON diet <i>vs</i>. HPDG diet, CON diet <i>vs</i>. DFS diet, and CON diet <i>vs</i>. WFS diet. In Exp. 1, 258 Nellore bulls were blocked by initial shrunk body weight (BW; 423 kg ± 36.6 kg), allocated into 44 pens in a randomized complete block design, and fed for 102 d. The average daily gain was greater (<i>P</i> = 0.02) for DFS than CON. Final BW (<i>P</i> <i>=</i> 0.02), hot carcass weight (HCW; <i>P</i> < 0.01), and <i>Longissimus</i> muscle area (<i>P</i> = 0.03) were greater for DFS than CON. In Exp. 2, 4 ruminally cannulated Nellore steers (initial BW = 389 ± 37 kg) were used in a Latin square design. Steers fed the WFS diet had less (<i>P</i> = 0.01) DMI than CON steers. The ether extract intake was greater (<i>P</i> = 0.02) for DFS and tended (<i>P</i> = 0.09) to be greater for WFS than CON, but HPDG did not differ from CON (<i>P</i> = 0.22). Steers fed DFS diets had 39.9% greater neutral detergent fiber intake (<i>P</i> < 0.01) than CON. Digestibility of DM was less (<i>P</i> < 0.01) for DFS than CON. Feeding HPDG and DFS decreased (<i>P</i> < 0.01) the molar proportion of rumen acetate, increased (<i>P</i> < 0.01) rumen propionate, and decreased acetate:propionate ratio (<i>P</i> < 0.01) compared to CON. Ruminal pH was not affected (<i>P</i> ≥ 0.82) by treatments, while ruminal ammonia nitrogen was greater for CON (<i>P</i> ≤ 0.01) compared with HPDG, DFS, and WFS. Feeding HPDG was a viable protein supplement alternative to sources like whole cottonseed and soybean meal in finishing diets. Feeding WFS and DFS improved cattle performance by displacing a portion of the flint corn and entirely replacing whole cottonseed and soybean meal.