Copper sulfide is also poorly absorbed. If high sulfur is a problem, adding copper carbonate may be recommended over copper sulfate to avoid adding more sulfur to the diet. Recent research suggests that organic-sulfur compounds may also affect copper absorption. With the increasing use of synthetic amino acids in the swine and poultry diets copper absorption could be depressed. In monogastrics, high levels of zinc, calcium, and iron can reduce copper absorption.
High calcium reduces copper absorption by increasing the pH of the intestinal contents.
Iron in the form of ferrous sulfide reduces copper absorption by forming insoluble copper sulfide. Typically nutrient requirements are determined in environments where disease and other stressors are minimized. As animal production intensifies, the requirement for nutrients involved in combating stress may also increase. For example, Orr et al. With chronic disease, liver copper stores may become depleted resulting in increased susceptibility to secondary infections.