COPPER-METABOLISM OF HOLSTEIN AND JERSEY COWS AND HEIFERS FED DIETS HIGH IN CUPRIC SULFATE OR COPPER PROTEINATE

Eight Holstein and 8 Jersey primiparous cows (3 d postcalving) and 8 H olstein and 8 Jersey growing heifers were randomly assigned to 1 of 8 treatments in a 2 x 2 x 2 factorial arrangement to compare Cu metaboli sm between Holsteins and Jerseys and the bioavailabilities of Cu in Cu proteinate and CuSO4. The variables were Holstein or Jersey, Cu suppl ementation at 5 or 80 mg/kg of DM, and supplements of CuSO4 or Cu prot einate. Jerseys had higher hepatic Cu concentrations than did Holstein s on d 60 (346 vs. 303 mu g/g of DM). At the high Cu supplementation, hepatic Cu increased more rapidly, and content was higher in Jerseys t han in Holsteins by d 60 (520 vs. 439 mu g/g of DM). On d 0, plasma Cu concentrations were 0.99 and 0.80 mu g/ml, and, on d 60, concentratio ns were 0.96 and 0.88 mu g/ml for Jerseys and Holsteins, respectively. Overall, serum ceruloplasmin oxidase activity was greater for Jerseys than for Holsteins. Jersey cows and heifers also had greater hepatic Fe (208 vs. 173 mu g/g of DM) and lower hepatic Zn (82 vs. 91 mu g/g o f DM) than did Holstein cows and heifers at d 60. The bioavailability of Cu in Cu proteinate and CuSO4 was the same. Plasma Cu concentration and ceruloplasmin have limited value as indicators of Cu status and a vailability to dairy cows and heifers.