Evaluation of NE predictions and the impact of feeding maize distillers dried grains with solubles (DDGS) with variable NE content on growth performance and carcass characteristics of growing-finishing pigs

Growing-finishing pigs (n = 432; initial body weight = 22.0 ± 4.3 kg) were utilized to measure growth performance and carcass characteristics when fed 4 sources of maize distillers dried grains with solubles (DDGS) with predicted net energy (NE) content ranging from 2083 to 2743 kcal/kg. Pigs were blocked by initial body weight, and within blocks, pens were randomly allotted to one of four dietary treatments (nine pigs/pen, 12 replicates/treatment). Dietary treatments consisted of four maize and soybean meal based diets containing 40% DDGS from (1) source A with low NE (LOW; 2083 kcal/kg), (2) source B with medium-low NE (ML; 2255 kcal/kg), (3) source C with medium-high NE (MH; 2469 kcal/kg), and (4) source D with high NE (HIGH; 2743 kcal/kg), based on NE estimates provided by a commercial service using a proprietary equation-based system. Experimental diets were formulated to meet or exceed nutrient requirements and contained similar standardized ileal digestible lysine:NE within phases. Overall, ADFI of pigs fed ML was greater (P < 0.05) than for pigs fed MH and HIGH, but not different from LOW, and no differences were observed among LOW, MH, and HIGH. Pigs fed ML had similar ADG with LOW and HIGH, but less (P < 0.05) than that of pigs fed MH, and no differences were observed among LOW, MH, and HIGH. Gain:feed was reduced (P < 0.02) in pigs fed ML compared with other dietary treatments. No treatment differences (P > 0.19) were observed in hot carcass weight, carcass yield, backfat depth, loin muscle area, and percentage of carcass fat-free lean among dietary treatments. The NRC (2012) model was used to estimate NE content of diets by matching the model-predicted G:F with the observed G:F. Using NRC (2012) NE content values for maize and soybean meal, NE content was calculated for DDGS sources LOW, ML, MH, and HIGH to be 2377, 1924, 2612, and 2513 kcal/kg, respectively. Predicted NE values from eight identified equations were calculated and compared with model-determined NE content of the 4 DDGS sources. Gain:feed responses of pigs indicated that the NE content estimates provided by the commercial service were overestimated for sources B and D, and underestimated for the sources A and C. Feeding 40% DDGS with less NE content increased ADFI and reduced ADG and G:F, but carcass traits were not affected when the difference of NE content was less than 700 kcal/kg among DDGS sources or less than 275 kcal/kg among dietary treatments.