Effects of feeding diets containing distillers’ dried grains with solubles and wheat middlings with equal predicted dietary net energy on growth performance and carcass composition of growing-finishing pigs

This experiment evaluated the effects of feeding distillers’ dried grains with solubles (DDGS) and wheat middlings (WM) in diets with similar estimated NE content on growth performance and carcass characteristics of growing-finishing pigs. Pigs (n = 384; 29.1 ± 3.6 kg initial BW) were blocked by initial BW, and within blocks, pens were randomly allotted to 1 of 4 dietary treatments (8 pigs/pen and 12 replicates/ treatment) in a 4-phase feeding program (29 to 50, 50 to 75, 75 to 100, and 100 to 120 kg BW). Dietary treatments were arranged in a 2 × 2 factorial design and formulated to consist of: 1) corn and soybean meal (CON), 2) CON with 30% DDGS, 3) CON with 15% WM, and 4) CON with 30% DDGS and 15% WM. Diets met or exceeded nutrient requirements published by the NRC (2012) and were formulated to contain the same concentrations of standardized ileal digestible (SID) Lys and meet or exceed minimum SID AA to Lys ratios within phases. No significant interactions for DDGS × WM × phase or DDGS × WM were observed for all growth performance criteria. Pigs fed diets containing 30% DDGS had reduced (P < 0.05) ADFI (1.76 vs. 1.86 kg/d) and ADG (0.85 vs. 0.91 kg/d) compared with pigs fed diets with no DDGS in phase 1 but not in other phases. The G:F of pigs fed diets containing DDGS was not different during phase 1 to 3 but was greater (P < 0.01) in phase 4 (0.313 vs. 0.291) compared with that of pigs fed diets with no DDGS. Pigs fed diets containing 15% WM had similar ADFI and G:F but reduced (P < 0.05) ADG (0.86 vs. 0.90 kg/d) compared with pigs fed diets without WM in phase 1, but no difference in ADG was observed in phases 2 to 4. No DDGS × WM interaction was observed for carcass traits. Pigs fed diets containing 30% DDGS had reduced (P < 0.01) HCW (86.5 vs. 89.9 kg), carcass yield (72.3 vs. 73.6%), LM area (45.0 vs. 47.9 cm²), and percentage of carcass fat-free lean (52.1 vs. 53.4%), but backfat depth was not affected compared with pigs fed diets with no DDGS. Pigs fed diets containing 15% WM had lower carcass yield (72.7 vs. 73.1%; P < 0.05) and HCW (87.7 vs. 88.7 kg; P < 0.10) than pigs fed diets with no addition of WM, but other carcass traits were not affected. In conclusion, overall ADG and G:F were not affected by feeding 30% DDGS or 15% WM when diets were formulated on the NE basis, but more accurate and dynamic estimation of NE content for DDGS sources is needed to optimize caloric efficiency at different physiological ages of pigs.