Endogenous Secretion and Reabsorption of 65Zinc in Ruminants as Affected by Zinc Deficiency and Feeding of Ethylenediaminetetraacetate or Cadmium

Open Access
Publisher Website
Google Scholar
Abstract
Using chromic oxide as a nonabsorbed marker, endogenous secretion and reabsorption of Zn65 in various segments of the gastrointestinal tract were studied in 7 Zn-deficient and 6 normal calves and in 8 deficient and 8 normal goats. All were fed a highly digestible low Zn purified diet. The animals were euthanatized 14 days following a single oral dose of Zn65; at which time all the gastrointestinal Zn65 was assumed to be of endogenous origin, though the amount present would be reduced by reabsorption. Dry matter digestibility, Zn65 and chromic oxide were determined in each section. Dry matter was absorbed in the rumen of both species with large amounts of secretion into the upper small intestine and reabsorption in the lower small intestine. Zn-65 was secreted into the rumen and reticulum followed by variable amounts of reabsorption in the abomasum. Large amounts of Zn65 were secreted into the anterior section of the small intestine with nearly all of it reabsorbed farther down the small intestine. The feeding of EDTA and Cd did not have a clear-cut effect on Zn65 or dry matter secretion or reabsorption in most sections. Likewise, a Zn-deficiency did not have a marked and consistent influence in most sections. There were appreciable differences in apparent dry matter and Zn65 secretion into the upper small intestine between calves which fasted overnight and goats fed 3 hr. prior to sacrifice. This effect was due to difference in the length of time since feeding the low residue diet.