EFFECT OF DIETARY NEUTRAL DETERGENT FIBER ON ILEAL DIGESTIBILITY AND PORTAL FLUX OF NITROGEN AND AMINO-ACIDS AND ON NITROGEN-UTILIZATION INGROWING PIGS

Two experiments were conducted to determine the effects of dietary NDF on apparent ileal and fecal digestibility and portal flux of nitrogen (N) and amino acids, and on N retention in growing pigs. In four equa l portions (at 0600, 1200, 1800, and 2400) barrows on Treatment B rece ived a basal diet, based on casein, cornstarch, and dextrose, at a fee ding level of 2.6 times energy for maintenance. Barrows on Treatment B +NDF received an additional amount of 15% (wt/wt) of purified wheat br an NDF (pNDF). In Exp. 1, four ileally cannulated barrows (40 to 75 kg ) were used in a crossover arrangement comprising two treatments and t hree periods. The addition of pNDF decreased ileal N digestibility fro m 94.1 to 88.9% (P < .001), whereas ileal digestibility of most amino acids was 2 to 5.5 percentage units lower (P < .001). Utilization of i leally digested N increased from 64 to 72% with the addition of pNDF, presumably because of the contribution of pNDF to the energy supply. I n Exp. 2, three barrows (30 to 54 kg) fitted with catheters in the por tal vein and the mesenteric vein and artery were used in a crossover a rrangement comprising two treatments and five periods. Portal absorpti on of nutrients was derived by multiplying the porto-arterial plasma c oncentration differences by portal vein plasma flow. The pNDF did not significantly affect the absorption of ileally digested amino acids an d the portal flux of ammonia and urea. The results showed that additio n of NDF reduced amino acid digestibility, but not the portal flux of digested amino acids, and NDF energy presumably improved utilization o f ileally digested amino acids.