Abstract
Summary
The effects of feeding a high but nontoxic zinc level to young rats for varied time periods on zinc metabolism and adaptations were investigated. Adding 600 ppm supplemental zinc to a “corn-soy” diet for periods from 7 to 42 days did not materially affect stable zinc level in any tissue studied. However, in every tissue, 65Zn retention from a single oral dose declined sharply with duration of added zinc feeding to 21 days, indicating a continuing adaptation in zinc metabolism for at least this period of time. Likewise, fecal 65Zn excretion increased with length of feeding time on high zinc, indicating a continuing reduction in net absorption for most of the 42-day period. When the data are compared with similar previous cattle studies, it is evident that there are major qualitative differences in zinc metabolism and homeostatic control between rats and cattle.
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