Case Study: Distillers grains supplementation in a forage system with spayed heifers

A 2-yr beef systems study evaluated winter and summer modified distillers grains plus solubles (MDGS) supplementation in a forage system. Treatments were arranged in a completely randomized design as a 2 × 2 factorial. Each year, 229 spayed heifers (215 ± 26 kg of BW) grazed corn residue 144 d, bromegrass 32 d (winter), and native range 120 d (summer) and were followed through the feedlot. Treatments included 0.91 kg of DM MDGS (LO) or 2.3 kg of DM MDGS (HI) supplement while grazing corn residue, and MDGS fed at 0.6% of BW daily (SUP) or no MDGS (NO SUP) during the summer. Winter ADG was 0.24 kg greater (P < 0.01) for HI than LO across both years. Summer ADG was 0.21 kg greater for SUP compared with NO SUP across both years (P < 0.01). Gains throughout the entire growing system were greatest for HI SUP, intermediate for HI NO SUP and LO SUP, and least for LO NO SUP. There were no interactions between winter and summer supplementation on ADG throughout the entire growing system (P ≥ 0.12). At the end of the feedlot phase, HCW was greater (P ≤ 0.03) by 23 and 15 kg (yr 1 and 2, respectively) for HI than LO. Summer SUP decreased finishing ADG by 0.21 kg (P = 0.02) in yr 1 and decreased G:F (P ≤ 0.07) both years. Across both years, profit was greater for HI than LO cattle (P ≤ 0.02), but summer supplementation did not affect profit (P = 0.15).