In vivo mineral contents of dietary fiber determined by EDX analysis

EDX measurements of the mineral content of oat hulls in the pig GI tract revealed that the hulls from the rectum contained more Na, P and S than prior to ingestion; while contents of K and Ca were not significantly different than in initial hulls. X-ray measurements indicated that potassium was the only element of the five examined which was unloaded from the initial oat hulls during passage through the GI tract. During this passage, the flows of Na and K into and out of oat hulls were proportional to concentrations of these elements in digesta. Although Ca was loaded onto oat hulls in the stomach, it was unloaded during subsequent passage, even though the concentration of Ca in digesta increased significantly in the large intestine. The behavior of corn pericarp generally was similar to that of oat hulls. We consider it unwise to attempt quantitative comparisons of corn pericarp behavior in our previous work (Dintzis et al., in press) with results in this study. The data bases are very small and feeding situations and diets were not equivalent. However, results from both studies show similar behavior in loading and unloading of Na, Ca, and S from the plant tissues, and possible differences with K and P. The finding that X-ray count values were different for oat hulls and corn pericarp when the tissues were loaded with equal amounts of calcium or potassium serves as a stark warning that additional work is required before measurements of this sort can provide quantitative results and a basis for comparisons between different plant tissues. Nevertheless, EDX analysis has provided information about the loading of Na, K, Ca, S, and P onto plant tissues during passage in the GI tract of growing pigs. The techniques used in this study appear worthy of further effort, for we believe they have the potential to provide significant information about in vivo interactions between plant tissues and minerals in the diet.