Dietary level and source of neutral detergent fiber and ileal endogenous nitrogen flow in pigs

Two experiments were conducted to study the effect of dietary level and source of neutral detergent fiber (NDF) on ileal dry matter flow and on total and endogenous N flow at the terminal ileum. Twenty-two crossbred 6-wk-old castrated male pigs with an average BW of 9 kg were used. The pigs were fitted with a post-valvular T-cecal cannula and two indwelling blood catheters. During the experimental period of 10 d, the pigs were 11 wk of age with an average BW of 14 kg. They were fed 2.6 times their maintenance requirement for energy of a corn starch-based, semisynthetic diet. The diets contained 178 g of soy isolate/kg as the only source of nitrogen (N). In diets of Exp. 1, purified NDF was included at 0 and 200 g/kg of feed at the expense of glucose. The diets of Exp. 2 contained one of the three different NDF sources (purified NDF, wheat bran, or sunflower hulls) at a level of 144 g of NDF/kg of DM. The purified NDF (pNDF) was isolated from the same batch as the wheat bran (WB) used in Exp. 2. The endogenous N flow at the terminal ileum of these pigs was determined with the 15N-isotope dilution method. The inclusion of NDF in the experimental diets increased (P < .05) the daily DM flow at the terminal ileum. Dry matter flow was increased .697 g for every g/kg increase in NDF in the diet. The different sources of dietary NDF gave similar (P > .05) ileal DM flows. The inclusion of pNDF (Exp. 1) increased (P < .05) the ileal flow of total N by 1.884 g/kg of dietary DM intake. This increase is composed of 59% endogenous and 41% exogenous N. With the inclusion of various NDF sources (Exp. 2), similar (P > .05) amounts of endogenous N passing the terminal ileum were obtained. Calculated from results of Exp. 1 and 2, endogenous ileal N flow was increased .008 g for every gram/kilogram increase in NDF in the diet. The total ileal N flow, however, varied (P < .05) with the inclusion of various NDF sources in the diets (Exp. 2). The results show that increase in ileal N with dietary NDF depend on level and type of NDF.