Evaluation of increasing dietary zinc on copper metabolism and on prevention of cumulative copper poisoning in sheep

Abstract

With the aim of analyze the effect of increasing doses of zinc in copper absorption and excretion mechanisms and the efficacy of zinc on copper poisoning prevention, will be utilized 50 male sheep randomly distributes in 5 groups with 10 animals each, according with the mineral solution given direct into rumen by fistula; Group 1 – solution with zinc (600 mg) and copper; Group 2 – solution with zinc (300 mg) and copper; Group 3 - solution with zinc (150 mg) and copper; Group 4 – Copper solution (positive control); Group 5 – Any solution (negative control). The groups 1 to 4 will receive daily 3 mg/kg/B.W. of copper in the first week, with an increasing of 3 mg/kg/B.W. in the dose, each week until the end of experiment, after 15 weeks. Will be performed 2 liver biopsies in all animals, in the beginning and the end of the study. Together with those chirurgic procedures, intestinal contend and bile will be sampled throughout punction. Will be evaluated the liver and bile copper and zinc concentration by spectrophotometer of atomic absorbance, and the concentration of intestinal and hepatic metalotionein. Blood samples will be taken weekly in all animals for determination of paced cell volume, copper and zinc concentration and AST and GGT activities. Even 5 week, total feces samples will be collected and measured for 6 days and each day a small sample will be keep for mineral determination. The absorption of Cu, Zn and Mo will be determinate throughout the difference of total mineral given and total excreted. The statistical analysis will be performed by analysis of variance with Tukey test for parametric data and Mann-Whitney or Friedman test for non parametric data.