Estimation of Endogenous Nitrogen and Amino Acids Flow at the Duodenum and Ileum in Growing Goats Fed on Different NDF Level Diets

An experiment was conducted with four ruminally, duodenally and ileally cannulated goats (15±0.5 kg) allocated to four dietary treatments in a 4×4 Latin square design to estimate the effects of dietary NDF levels on the losses of endogenous nitrogen (EN) and endogenous amino acids at the duodenum and ileum in goats. Goats were fed the total mixed diets containing four levels of NDF (39.69, 36.95, 34.22 and 31.49%). The duodenal flow of EN and AA was determined by the difference and amino acid profile (AAP) method, respectively. The ileal flow of EN and AA was measured by the water soluble protein method. The duodenal flow of EN estimated by the two methods were not affected (P>0.05) by the dietary NDF content. For the estimated values by the AAP method, the duodenal flow of endogenous AA expressed less variation than those by the difference method. When compared with the difference method, the duodenal flow and the re-absorption of endogenous N and AA were higher than those estimated by the AAP method. The results implied that dietary fiber content might influence the secretion of endogenous protein and the more reasonable estimates of endogenous N and AA could be obtained by the AAP method.