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The objective of this study was to determine the effect of increasing levels of sorghum dry distillers grains with solubles (DDGS) in high concentrate feedlot diets in the nutrient digestibility (%), ruminal degradability (%), pH, NH4 (µg N-NH4/ml) and volatile fatty acid (VFA, mM/l) concentration. Four ruminally cannulated steers (450 ± 63 kg) were used in a 4x4 Latin square design, evaluating four treatments in four periods of 19 days each, with 14 days of adaptation and 5 days of measurements. Animals received a TMR, 92% concentrate (63% sorghum grain, 25% soybean meal, 4% mineral commercial premix), with DDGS (90% DM, 29% CP, 51% NDF, 9% EE) in increasing levels generating 4 treatments: 0, 15, 30, or 45%. Replacing a combination of sorghum grain and soybean meal to maintain diets isoproteic. The TMR was offered ad-libitum to each animal in individual pens. Greater levels of DDGS increased the consumption of NDF (P = 0.0001) and EE (P = 0.0004), and NDF total tract apparent digestibility (linear; P = 0.038), but it decreased quadratically EE total tract apparent digestibility (P = 0.017). The DM (84.2 ± 0.17) and the CP total tract apparent digestibility (85.3 ± 2.0) was not affected by increasing levels of DDGS. Nevertheless, the ruminal degradability of total DM (P = 0.01) and CP decreased linearly (P = 0.01), without affecting NDF degradability (65.6 ± 4.3). Increasing levels of DDGS did not change ruminal pH (5.6 ± 0.14), acetate (45.1 ± 6.3), propionate (24.8 ± 3.6), and butyrate (5.2 ± 0.7) concentration, but NH4 concentration decreased linearly (P < 0.0001) directly related to the decreased CP ruminal degradability. Increasing levels of DDGS inclusion in a high concentrate diet reduce the CP ruminal degradability, without changes in total CP digestibility, what indicates a change of the site of digestion. [ABSTRACT FROM AUTHOR]

• Sorghum DDGS is a suitable ingredient for feedlot cattle diets. • Optimum level of sorghum DDGS in the diet to maximize calf growth is around 20%. • Feeding sorghum DDGS up to 45% of growing cattle' diet reduces gain efficiency and NEg. • Sorghum DDGS in a high grain ration improves physically effective fiber supply. The objective of this study was to determine the effect of concentrations of sorghum dried distillers' grains plus solubles (SDDGS) in growing feedlot diets on animal performance, ruminal passage rate and digestion. Two experiments were conducted evaluating four isonitrogenous total mixed rations (TMR) as dietary treatments, offered ad-libitum , with increasing levels of SDDGS 0%, 15%, 30%, and 45%, replacing a combination of sorghum grain and soybean meal. In Experiment 1, 32 Hereford steers (198.8 ± 14.6 kg) were randomly assigned to one of four dietary treatments and fed in individual pens over the course of 70 days. Average daily gain, final BW, and ribeye area exhibited a quadratic response (P ≤ 0.05). Reaching maximum values with 18.2% to 19.6% of SDDGS concentration in the TMR. There were no differences in DM intake and backfat thickness (P ≥ 0.23). Feed efficiency (P = 0.0002) and dietary net energy (P = 0.027) decreased linearly with greater SDDGS concentration in the TMR. Based on growth performance data, the estimated SDDGS NE value was similar to grain sorghum at inclusion level of 30%, but at higher levels of inclusion, the energy value of SDDGS was negatively affected, with a decrease of 24% for 45% inclusion level. In Experiment 2, four ruminally cannulated steers (450 ± 63 kg) were assigned to the same dietary treatments as in Experiment 1 in a 4 × 4 Latin square design. Physically effective fiber (peNDF) and NDF content of the TMR increased linearly (P < 0.0001) with increasing levels of SDDGS. Greater concentrations of SDDGS in the TMR led to a linear increase in NDF and EE intake (P < 0.001) with no effect on DM and CP intake (P ≥ 0.17). Metabolizable energy intake (P = 0.09) demonstrated a linear tendency of increase with greater SDDGS concentration. Ruminal degradability of DM and CP decreased linearly (P ≤ 0.01). Ammonia concentration decreased linearly (P < 0.0001) with no changes in ruminal pH (P ≥ 0.75) as concentrations of SDDGS increased. Sorghum DDGS is a suitable ingredient for feedlot cattle diets. At 15% and 30% inclusion level, the NE value of SDDGS is similar than sorghum grain, and allows to achieve a greater growth performance. Replacing sorghum grain beyond 30% with SDDGS, the NE value of SDGGS linearly decrease by increasing dietary lipid and by replacing starch of grain with NDF of SDDGS. [ABSTRACT FROM AUTHOR]