Effects of inclusion rate of high fiber dietary ingredients on apparent ileal, hindgut, and total tract digestibility of dry matter and nutrients in ingredients fed to growing pigs

An experiment was conducted to determine if values for the coefficient of ileal apparent digestibility (CLAD), the coefficient of hindgut apparent disappearance (CHAD), and the coefficient of total tract apparent digestibility (CTTAD) of dry matter (DM) and nutrients in high-fiber ingredients measured at 150 g/kg inclusion are also accurate if measured at 300 g/kg inclusion in diets fed to pigs. The second objective was to confirm that most of the insoluble dietary fiber (IDF) is not fermented by growing pigs. Twenty ileal-cannulated pigs (BW: 30.64 +/- 2.09 kg) were allotted to a replicated 10 x 4 incomplete Latin Square design with 10 diets and four 26-d periods. There were 2 pigs per diet in each period for a total of 8 replications per diet. A corn and soybean meal (SBM) basal diet and a corn-SBM diet with 300 g/kg corn starch were formulated. Six diets were formulated by replacing 150 or 300 g/kg corn starch by 150 or 300 g/kg corn germ meal (CGM), sugar beet pulp (SBP), or wheat middlings (WM). Two additional diets were formulated by adding 150 or 300 g/kg canola meal (CM) to the diet containing corn, SBM, and 300 g/kg corn starch at the expense of corn and SBM. Effects of inclusion rate of each fiber source in the diet on CLAD, CHAD, and CTTAD of DM and nutrients were analyzed using orthogonal contrasts. Independent t-tests were used to compare inclusion rates within each ingredient. Results indicated that CLAD and CHAD of CP, acid hydrolyzed ether extract (AEE), and most fiber fractions in CM decreased (P < 0.05) as inclusion level increased from 150 to 300 g/kg, but that was not the case for CGM, SBP, or WM. The CTTAD of DM, organic matter (OM), AEE, and soluble dietary fiber (SDF) in CGM increased (P < 0.05) if 300 g/kg rather than 150 g/kg was included in the diet and CTTAD of DM, OM, acid detergent fiber, and SDF in WM increased (P < 0.05) as inclusion level increased. No differences in CTTAD of DM and nutrients in CM and SBP were observed between inclusion rates. The CTTAD of IDF ranged from 0.529 in WM included at 150 g/kg to 0.862 in SBP included at 300 g/kg in the diet. In conclusion, CLAD, CHAD, and CTTAD of most nutrients in test ingredients is not different between 150 and 300 g/kg inclusion rate. Under the conditions of this experiment, there was relatively high digestibility of IDF.