Movement and Absorption of Major Minerals and Water in Ovine Gastrointestinal Tract

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Abstract
Movement of Ca, Cl, Mg, K, Na and water in the intestine of sheep was determined with 141Ce as an unabsorbed reference substance. Net secretion of P and Na, but not of K and Ca, was observed to the rumen. Water disappeared from the omasum and was secreted in the abomasum. Cl secretion occurred in the omasum and more in the abomasum. Extensive secretion in the duodenum increased flows of Na and K 8-9-fold, Ca, Cl and P 3-6-fold, Mg 1.3-fold and water 12-fold. Reabsorption was rapid in the small intestine, the major site of disappearance of all ions. Rates of disappearance decreased with increasing distance from the pylorus. Little further net disappearance of Ca, P, Mg or K was found in the large intestine; water, Na and Cl disappearance continued. Overall absorption Na, K and Cl, .apprx. 90%, P 63%, Ca 38% and Mg 71%. This study highlighted the importance of endogenous secretions in mineral absorption in the sheep.