Effect of level of dietary neutral detergent fiber on ileal apparent digestibility and ileal nitrogen losses in pigs.

A study was conducted with 20 barrows (average BW 25 kg) to determine the effect of various levels of neutral detergent fiber (NDF) in the diet on the apparent ileal nutrient digestibility and ileal diaminopimelic acid (DAPA) content, and consequently on the amount of ileal endogenous nitrogen. The pigs were fitted with a post-valvular T-cecal cannula. They were fed .8 kg/d of a corn starch-based semisynthetic diet formulated to contain equal amounts of protein and starch and 0, 60, 120, or 180 g of purified NDF/kg of diet, included at the expense of glucose. The purified NDF (pNDF) was isolated from wheat bran using an incubation procedure with pancreatin. Ileal digestibility of NDF was approximately 17% and was independent of the pNDF level in the diet. By increasing the amount of pNDF in the diets, apparent ileal digestibilities of dry matter (DM), nitrogen (N), neutral detergent insoluble N (NDF-N), and ash decreased linearly (P < .05). The DAPA content of the ileal digesta (g/d) was not affected by the percentage of pNDF in the diets. Calculation of the ileal bacterial N excretion indicated that more than 50% of the ileal N was of bacterial origin. With increased percentage of dietary pNDF, both endogenous and exogenous N in ileal chyme were linearly increased (P < .05). Thus, an increase in the dietary fiber content leads to a decreased apparent ileal protein digestibility due to increased ileal losses of both endogenous and exogenous protein.