The present study compares the use different levels of dietary zinc oxide and zinc/copper ratios on the metabolism of iron (Fe) in weaned pigs. Two experiments were conducted using 120 and 160 weanling piglets (7.96 ± 1.17 kg and 7.81 ± 0.25 kg body weight, respectively) that were randomly assigned to the experimental treatments. Experiment I: diets supplemented with 100, 1,000, and 3,000 mg/kg of zinc (Zn) as ZnO (LZn, MZn, HZn) and 130 mg/kg of copper (Cu) as CuSO4; experiment II: diets supplemented with 100 or 3,000 mg/kg of Zn as ZnO (LZn and HZn) in combination with 6 or 130 mg/kg of Cu as CuSO4 (LCu and HCu). In both experiments, diets had similar levels of supplemental Fe (100 mg/kg of Fe as FeSO4). Piglets were slaughtered at d21 (weaning), d23 (experiment I), d28 (experiment II), d35, and d42 to assess whole blood, serum, and liver Fe concentrations, hemoglobin concentration, and the relative expression of key genes associated with Fe metabolism in jejunum and liver. Whole blood Fe and hemoglobin concentrations (experiment I) as well as serum Fe concentrations (experiments I and II) were not affected by dietary treatments (P ≥ 0.11). Liver Fe concentrations (experiment II) and total liver Fe content (experiments I and II) were lower (P ≤ 0.05) in HZn compared to LZn groups at d42. In both experiments, the mRNA expression of jejunal DMT1 was lowest and that of jejunal FTH1 was highest at d42 (P ≤ 0.04) for HZn piglets. In experiment II only, jejunal FTH1 and FPN1 expression were greater (P ≤ 0.04) in HCu compared to LCu groups at d42. The highest expression of hepatic FTH1 and FPN1 at d35 and d42 (P ≤ 0.02) was detected in HZn piglets in both experiments. For hepatic HAMP, expression values were greater (P = 0.04) at d42 in HZn groups. In conclusion, high dietary ZnO levels impair Fe metabolism but the effects are not intense enough to impact circulating Fe and hemoglobin concentrations.
Keywords: copper; iron; metabolism; pig; zinc.
Zinc oxide and copper sulfate are commonly used to prevent diarrhea in weaned piglets as an alternative to antibiotics. However, this strategy has been questioned due to environmental issues and public health concerns related to bacterial resistance. Recently, it was reported that high dietary zinc levels and/or high dietary zinc/copper ratios impair zinc and copper homeostasis and are detrimental to postweaning piglets’ health. However, the eventual effects on iron metabolism are much less explored in pigs. Therefore, two experiments were conducted to evaluate the effects of increasing levels of dietary zinc (100, 1,000, and 3,000 mg/kg) and of different dietary zinc/copper ratios (3,000/130, 3,000/6, 100/130, and 100/6 mg/kg) on iron metabolism in weaned piglets. This study demonstrates that high dietary zinc levels, independently of dietary copper levels, impair iron metabolism by systemic and local (intestinal) mechanisms but also suggests that preweaning factors may interfere with postweaning iron homeostasis.
© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food, Government of Canada, 2023.