DIETARY FIBER VISCOSITY AND ENDOGENOUS PROTEIN EXCRETION AT THE TERMINAL ILEUM OF GROWING RATS

The effect of dietary fiber viscosity on the excretion of endogenous n itrogen and amino acids from the small intestinal lumen of growing rat s was investigated. Rats were fed for 12 d protein-free diets containi ng 5% cellulose (negligible viscosity) or 5% carboxymethylcellulose of low (20 cP), medium (800 cP) or high (2000 cP) viscosity, as the sole dietary fiber source. As dietary fiber viscosity increased from 0 to 2000 cP, there was a significant (P < 0.05) linear increase in the flo w of endogenous nitrogen, aspartic acid, serine, glutamic acid, prolin e, threonine, glycine, alanine, isoleucine, histidine, valine, methion ine, leucine and lysine at the terminal ileum. The amino acid composit ion of the ileal digesta was unaffected by changes in fiber viscosity. It seems that either endogenous protein of a similar origin was secre ted in larger amounts or that the digestion and absorption of endogeno us amino acids was inhibited as dietary fiber viscosity increased. The re was a significant (P < 0.05) linear increase in the concentration o f sialic acids relative to chromic oxide in the small intestinal conte nts with increasing fiber viscosity, indicating an increase in mucopro teins.