Secretion and absorption of nutrients in the alimentary tract of reindeer fed lichens or concentrates during the winter

Abstract

Water, organic matter (OM), N, Ca, P, K, Na, and Cl exchange was estimated in the alimentary tract of reindeer given concentrate or lichen diets alone or supplemented with minerals. Chromic oxide was used as a nondigestible marker and results are discussed in relation to inaccuracies of this marker technique. The pattern of water, OM, and N exchange was similar to other ruminants; over 61% of OM digestion was due to the rumen–reticulum plus omasum and abomasum (stomachs). For the concentrate diet, 40–60% of N digestion occurred in the stomachs. Apparent absorption of Ca, P, and Mg in the stomachs was linearly related to intake. Ca and Mg supplemented to lichens was excreted because of an inability of the intestines to recover mineral secreted into duodenal contents. In contrast, the jejunum absorbed P added to the diet. Excretion of K in feces at 0.076 mM/g fecal dry matter placed a limit on K absorption; it was negative on the lichen diet. Cl was absorbed in the small and large intestines. Supplemental Na, part of the P, Ca, and K, but none of the supplemental Mg added to the lichen diet was absorbed. Lichens appeared to bind some minerals and could thereby place a limit on their absorption.