Effect of fiber source and enzyme addition on the apparent digestibility of nutrients and physicochemical properties of digesta in cannulated growing pigs

To evaluate the effect of fiber source and enzyme addition on the nutrient digestibility of cereal by-product based diets, wheat bran and soybean hull were used as sole fiber source to prepare 2 basal diets (wheat bran-based diet, WB and soybean hull-based diet, SH). After supplementing an enzyme mixture in the 2 basal diets, one of 4 test diets (WB and enzyme added WB, SH and enzyme added SH) was allotted to 2 of 8 male growing pigs that were surgically fitted with T-shape cannulas at proximal duodenum and distal ileum simultaneously, according to a 4 × 4 Latin square design. Duodenal and ileal digesta and feces were collected to measure the coefficient of apparent digestibility of crude protein (CP), ether extract (EE), starch, organic matter (OM), neutral detergent fiber (NDF), acid detergent fiber (ADF), non-starch polysaccharides (NSP) and its constituent sugar residues at proximal duodenum (CADD), distal ileum (CAID) and total digestive tract (CATTD) of pigs, and to evaluate their physicochemical properties as well. The result indicated that the digestion of most of nutrients including fiber and NSP fractions commenced with considerable extent prior to proximal duodenum in all diets. The wheat bran shown higher CAID of NDF (P < 0.001) and ADF (P = 0.001), and CATTD of CP (P < 0.001) and EE (P = 0.005) than soybean hull. Despite fiber source did not affect CATTD of NSP fractions, the total NSP (P < 0.001), arabinose (P = 0.030), xylose (P < 0.001) and glucose (P = 0.001), and insoluble NSP (P < 0.001), arabinose (P < 0.001) and glucose (P = 0.003) of wheat bran were more digestible at terminal ileum than that of soybean hull. Enzyme addition improved the CADD of OM (P = 0.002), ash (P = 0.045), NDF (P = 0.004) and ADF (P < 0.001); and the CAID of CP (P = 0.006), EE (P = 0.001), OM (P = 0.029), ash (P = 0.003), NDF (P = 0.006) and ADF (P = 0.002), but did not affect the CATTD of other gross nutrients. The CADD and CAID, but not CATTD, of most of NSP fractions and their constituent sugar residues were affected by enzyme addition. The fiber source and enzyme addition also showed influence on digesta viscosity, water binding capacity (WBC) and pH value of digesta and feces. In conclusion, dietary fiber source influenced the digestion of nutrients at different segments of pig digestive tract with higher CATTD of CP and EE of wheat bran than that of soybean hull. Exogenous NSP-degrading enzyme accelerated the degradation of fiber and NSP fractions, and promoted nutrient digestion in the fore-gut of pigs. It is of high potential to improve the efficiency of energy and nutrient utilization of fibrous cereal by-products.