65Zn Absorption Rate Following Single Duodenal Dosing in Calves Fed Zinc-deficient or Control Diets

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Abstract
Effects of dietary zinc level on 65Zn absorption and its movement in the intestinal tract were studied in calves fed zinc-deficient (5 ppm Zn) and control (37 ppm Zn) purified diets for 2 weeks. The calves were killed at 1, 4, 8, and 24 hours after dosing via duodenal catheter. Absorption, defined as 65Zn unrecovered in intestinal contents and feces, was very rapid during the first hour for both dietary treatments. After 1 hour, absorption progressively diminished with little absorption after 8 hours. The deficient diet substantially increased 65Zn absorption. Blood 65Zn levels increased sharply during the first 0.5 hour and tended to decline from 1 to 24 hours. Liver and kidney 65Zn values reflected absorption and in conjunction with blood data indicated that 65Zn, following removal from the intestinal contents, was rapidly transferred to the blood and transported to body tissues. Passage of 65Zn down the small intestine was rapid and substantially faster for control than for deficient-fed calves. In controls at 4 hours, most of the unabsorbed 65Zn was beyond the small intestine. Relating intestinal movement data to 65Zn absorption suggested that little absorption occured in the cecum or beyond.