Case study: Use of dried distillers grains, soybean hulls, or both to background beef calves fed bahiagrass hay

Two experiments were conducted to evaluate dried distillers grains (DDG), soybean hulls (SBH), and a slow-release urea (SRU) product as supplements to background beef steer calves. In both experiments, 56 Angus steers were individually supplemented for 42 d and provided ad libitum access to bahiagrass (Paspalum notatum) hay. On d 0, 14, 28, and 42, BW were recorded and blood samples were collected. In Exp. 1, steers (BW = 236 ± 26 kg) were randomly allotted to 1 of 4 supplement treatments: 1) DDG (1.19 kg/d), 2) DDG+SRU (1.19 kg/d of DDG + 45.5 g/d of SRU), 3) SBH (2.63 kg/d), or 4) SBH+SRU (2.63 kg/d of SBH + 45.5 g/d of SRU). Final BW did not differ (P ≥ 0.74); however, 42-d BW gain was greater (P = 0.05) and estimated mean total DMI was greater (P < 0.002) for calves consuming SBH supplements compared with those eating DDG. Addition of SRU did not affect (P ≥ 0.29) steer performance or DMI. Plasma glucose concentrations were not affected by supplement (P ≥ 0.12) or SRU (P ≥ 0.22). No interaction of supplement and SRU was detected (P ≥ 0.10). Concentrations of plasma urea N were greater (P < 0.001) for DDG compared with SBH, and SRU increased plasma urea N (P ≤ 0.05). In Exp. 2, steers (BW = 274 ± 26 kg) from Exp. 1 were randomly allotted to 1 of 4 supplement treatments: 1) DDG (2.8 kg/d), 2) DDG/SBH (1.93 kg/d of DDG, 0.98 kg/d of SBH), 3) SBH/DDG (0.96 kg/d of DDG, 2.05 kg/d of SBH), or 4) SBH (3.12 kg/d). Supplement treatment had no effect (P = 0.79) on final BW. Across all 42 d, ADG of SBH-supplemented steers were less than those of DDG/SBH (P = 0.05) and SBH/DDG steers (P = 0.03) but similar to those of DDG steers (P = 0.45). Estimated mean hay DMI and estimated total DMI were less (P < 0.05) for the DDG-treatment steers compared with those of the other 3 treatments. Plasma glucose concentrations were not different (P = 0.85) between treatments. Concentration of plasma urea N increased (P < 0.001) with increased inclusion of DDG in the supplement on d 14, 28, and 42. Supplementing steers consuming forage with a combination of coproducts optimized calf performance. Steer cost of gain was similar (P ≥ 0.37) among treatments that included DDG, and less (P ≤ 0.04) than SBH only; therefore, the cost of coproduct feedstuffs would dictate the optimal proportions.