Effects of Selected Polysaccharides on the Bioavailability of Pyridoxine in Rats and Chicks

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Abstract
The effects of cellulose, pectin and bran on the bioavailability of pyridoxine (PN) were examined using rat and chick bioassay methods. Dose-response curves for growth, feed consumption, feed efficiency and either liver pyridoxal 5′-phosphate (PLP) or erythrocyte aspartate aminotransferase (Asp-AT) activity and PLP stimulation in vitro were compared among animals fed experimental diets varying in dietary fiber source and suboptimal levels of PN. In rats, the observed stimulation of growth and feed efficiency by pectin, as compared to cellulose, at suboptimal PN levels was attributed to increased synthesis of vitamin B-6 by intestinal microflora. Diets containing pectin markedly increased the fecal vitamin B-6 content. No difference in liver PLP was detected among rats fed various diets. In chicks, 5% dietary pectin resulted in increased feed consumption, but also diarrhea and depressed growth. Asp-AT activities at the lower level of dietary PN showed a significant (P < 0.05) but modest stimulating effect of pectin on the apparent bioavailability of PN. Bran resulted in a 17% bioavailability decrease of PN as indicated by growth and feed consumption data in the chick. However, no difference in Asp-AT activity or in vitro PLP stimulation was detected in comparison of responses from bran-fed chicks with the standard responses. These results suggest that the polysaccharides tested did not have important deleterious effects on the bioavailability of pyridoxine.