Short-term high level zinc feeding and tissue zinc concentration in mature laying hens

Two trials were conducted to study the effects of high dietary Zn on tissue Zn accumulation and depletion in laying hens. Hens laying at approximately 60 to 70% were fed a diet containing 20 g Zn as ZnO/kg diet (as fed) for 4 days. For the remaining 18 days, hens were fed the same diet without the 20 g added Zn/kg diet. Ten hens were killed at initiation of the experiment (Day 0), and liver, kidney, and pancreas were obtained for Zn analysis. On Days 1, 2, 3, 4, 10, 16, and 22, similar samples were obtained from 10 hens. Feeding high Zn for 4 days caused a reduction in ovary and oviduct weight by Day 10. Liver, kidney and pancreas Zn concentrations increased approximately 10, 3, and 25-fold, respectively, in birds following 4 days of feeding the high Zn diets. The liver and kidney Zn concentrations returned to pretreatment concentrations within 18 days after the birds were fed the control diets (Day 22). The pancreas maintained higher Zn concentrations in comparison with the other tissues following withdrawal of the high Zn diet.