Responses of Lactating Dairy Cows to Copper Source, Supplementation Rate, and Dietary Antagonist (Iron)

¹ Department of Dairy and Poultry Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32611-0920
² Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32611-0920

Forty-eight lactating Holstein cows were fed low-Cu diets with 500 mg of supplemental Fe/kg of dry matter (DM), a Cu antagonist, for a 30-d Cu-depletion period. After depletion, two Fe treatments (0 and 500 mg of Fe/kg of dietary DM) and five Cu treatments (2 x 5 factorial arrangement) were compared over 83 d. The Cu treatments were control (basal diet containing 8 mg of Cu/kg of DM) and either 15 or 30 mg of supplemental Cu/kg of dietary DM from either CuSO₄ or Cu-lysine. Feeding 500 mg of supplemental Fe/kg of DM (in addition to basal dietary concentration of 140 mg Fe/kg) depressed liver Cu in the absence of Cu supplementation. Apparent Cu retention, estimated from Cu intake minus fecal Cu, was increased greatly by Cu supplementation immediately after the depletion period but declined to very low net retention by d 45 of the 83-d experiment. There were no differences detected between CuSO₄ and Cu-lysine except a tendency over time for Cu-lysine to maintain higher plasma Cu, especially in the absence of the Fe antagonist.

Key Words: copper • iron • dairy cattle

Submitted on August 23, 1999
Accepted on January 21, 2000

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