COMPARISON OF COPPER SULFATE AND COPPER PROTEINATE AS COPPER SOURCES FOR COPPER-DEPLETED STEERS FED HIGH MOLYBDENUM DIETS

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Abstract
Copper (Cu) depleted steers were used to compare copper sulfate and copper proteinate as Cu sources for cattle consuming high molybdenum diets. Two experiments utilizing corn silage and barley concentrate diets with 10 mg added Mo kg−1 DM were undertaken. Experiment A was a 105-d study in which an 83:17 ratio of silage to concentrate was fed, whereas, experiment B was an 84-d study comparing the same Cu treatments for cattle fed a 26:74 (Low) or a 64:36 (High) ratio of silage to concentrate. Cu treatments for both experiments were: no supplemental Cu (0Cu); a dietary supplement of 10 mg Cu kg−1 DM added as copper sulfate (CuSO); and a dietary supplement of 10 mg Cu kg−1 DM added as copper proteinate (CuPro). Both Cu supplements improved (P < 0.05) concentrations of Cu in plasma for both experiments and improved (P < 0.05) concentration of Cu in liver for experiment B. Copper supplementation (P < 0.05) reduced plasma Mo concentrations in experiment A relative to animals receiving no supplemental Cu. Both Cu sources resulted in reduced rumen fluid soluble Mo concentrations. Steers in experiment A had lower initial liver and plasma Cu concentrations than was observed for experiment B. Average daily gains for steers consuming CuPro were 16.8% greater (P < 0.05) than for 0Cu with CuSO being intermediate for experiment A. Results indicate that the bioavailability of Cu from Cu proteinate is similar to that of copper sulfate in-Cu depleted steers consuming diets containing excess Mo. Key words: Cattle, copper sulfate, copper proteinate, copper, molybdenum