Evaluating the Effect of Adaptation Length on Apparent Ileal and Total Tract Digestible Energy of Corn and Wheat Middlings in Growing Pigs

This study investigated the effect of adaptation length of corn- and wheat middlings (WM)-based diets on apparent ileal and total tract digestible energy (DE) of corn and WM using the difference method. Twenty-one ileal cannulated pigs (BW=34.1 ± 1.5 kg) were allotted in a 3 × 3 factorial arrangement of treatments using the randomized complete block design with 3 diets (reference, reference+corn, or reference+WM) and 3 adaptation lengths (4, 8, and 12 days). Each pig was fed 4% of the BW of the lightest pig within each block. Reference+corn and reference+WM diets were produced by replacing 30% of the energy yielding components of the reference diet (corn-SBM-based) with corn or WM, respectively. Ileal and fecal samples were collected on days 4, 8, and 12. Proc mixed model of SAS was used to analyze the data and a repeated statement was included to account for correlated observations made on the same animal. The main effect of diet type on ileal and total tract DE, dry matter (DM) and energy (EN) digestibility was different with reference+WM diet having lower (P<0.05) values. Diets, total tract DE (2.7%), DM (2.6%) and EN (2.8%) digestibility increased (P<0.05; linear and quadratic effect) with increasing adaptation length. Ileal (3,325 vs 1,778 kcal/kg) and total tract (3,668 vs 2,864 kcal/kg) DE of corn was higher (P<0.05) than that of WM. Hindgut EN disappearance showed a tendency to increase (P=0.058) linearly with adaptation length (index method). Energy loss in the hindgut from the reference+WM diet was higher (P<0.05) compared to that of the reference diet (subtraction method). Data from this study showed that the DE of corn and WM increased by 10 and 61%, respectively, between the ileal and total tract values. Finally, four days of adaptation is sufficient for corn and WM ileal and total tract DE determination.