Supplementation of Copper as Copper Sulfate or Copper Proteinate for Growing Calves Fed Forages Containing Molybdenum

Abstract

Holstein calves (age>12 wk old) were assigned to dietary treatments of 1) no supplemental copper, 2) copper proteinate, or 3) copper sulfate. The copper supplements were incorporated into premixes and added to a pelleted concentrate. The concentrates were fed at 1.8kg per head per d and contained 5, 19, or 19ppm copper and .6ppm molybdenum by analysis. All calves were fed a grass hay free-choice, which contained 1ppm copper and 5ppm molybdenum. Ratios of copper to molybdenum were .9, 2.8, and 2.8 for diets 1, 2, and 3, respectively. Copper concentrations in plasma were significantly greater at wk 12 in calves fed copper proteinate than control or calves supplemented with copper sulfate. Liver copper also was higher at wk 12 in calves fed copper proteinate. Final body weights, plasma zinc, plasma iron, hemoglobin, and hematocrit were not affected by treatment. Bioavailability of dietary copper from copper proteinate was greater than from copper sulfate for calves fed diets containing molybdenum.