Evaluation of sorghum dried distillers’ grains plus solubles as a replacement of a portion of sorghum grain and soybean meal in growing diets for steers

Abstract

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.