In fact, this was also apparent in trial, although absolute values were different.Vitamin B absorption in humans occurs through an active process mediated by ileal intrinsic factor and enterocyte transcobalamin at reduced dietary content, whereas, at greater dietary content of vitamin B, after saturation with the active absorption process, the excess vitamin would be absorbed by passive intestinal diffusion. The retention approach underestimated, in theory, intestinal absorption because part of the vitamin B absorbed during the experimental period of dwas used for metabolism and, then, catabolized.On the other hand, the portal appearance approach also underestimated intestinal absorption because part of the vitamin B absorbed after the meal is retained or retained and used directly by the intestinal tissue before reaching the portal vein.In the portal appearance approach, it can be estimated, from results in trial, that at least and of the absorbed vitamin B is retained in the digestive tract for B and B, respectively.This retention represented, therefore, the minimal amount of absorbed vitamin B, which is not accounted for by the portal appearance approach in trial. Other aspects of the digestive physiology relative to vitamin B might be involved in the differences between the approaches.Some vitamin B can be detected in the lymph of rats after an oral bolus of vitamin B.The lymph carries vitamin B coming directly from the intestinal lumen and from blood circulation; the former would represent between to of the intestinal absorption of this vitamin. If the situation is similar in pigs, it can be hypothesized that a small quantity of vitamin B absorbed through the lymphatic system in trial was not accounted for in the calculation of bioavailability by portoarterial differences.This could be another contributing factor, although small, for the discrepancy between the approaches for estimation of bioavailability.In the retention approach in trial, each pig received a daily supplement of vitamin B for consecutive days, whereas in trial, each pig received each level of supplement only once according to a crossover design.Although all the aforementioned factors related to digestive physiology of vitamin B can <a href="http://www.targetmol.com/compound/D-Cycloserine">Targetmol's
D-Cycloserine</a> contribute to differences of bioavailability measurements between the trials, their relative importance cannot be determined with the present available information.In summary, although the estimations of bioavailability varied according to the approach chosen, it was nevertheless possible to differentiate the impact of dietary vitamin B on its bioavailability as previously reported for humans.A daily dietary supplementation of g, which is greater than NRC, seemed adequate to maximize vitamin B in liver and to attenuate the nycthemeral decrease in arterial plasma concentrations of vitamin B. Absorption of cyanocobalamin by suckling piglets.Influence of vitamin Bbinding protein from sows milk on uptake of vitamin B by microvillus membrane vesicles prepared from small intestine of the piglet.J. Anim. Sci. We have further shown that the vitamin B, activities of a variety of natural materials, extracted in the presence of cyanide, were contributed by one or more of these five compounds.Clearly, the presence in such test extracts of these vitamin B, like compounds, singly or in combination, can greatly complicate the assessment of cyanocobalamin itself by the available nonspecific techniques of assay.