Gastrointestinal Sites of Absorption and Endogenous Secretion of Zinc in Dairy Cattle

Two nonabsorbed marker techniques (Ce~'Cl~ and Cr~_O~) were compared for determining sites of gastrointestinal absorption or secretion of radiozine in dairy cattle. Zinc was absorbed from the abomasum and lower small intestine, whereas absorption or excretion below the cecum was negligible. Secretion of endogenous zinc occurred in the upper part of the small intestine. Net absorption of Zn ~ administered daily averaged 12% in mature cows, 20% in calves ranging from 5 to 12 months, and 55% in week-old calves. Values determined using Ce ~' and Cr~Os as markers were ill good agreement.