EFFECT OF COPPER SOURCE AND LEVEL ON THE COPPER STATUS OF HOLSTEIN HEIFERS RECEIVING HIGH DOSES OF ZINC

摘要

A 31-day study was conducted to determine the effect of supplemental Cu source (CuSO_4 vs Availa-Cu) and level (15 or 30 ppm) on the Cu status of heifers receiving high doses of Zn. Treatments consisted of feed sources of Cu (Feed-Cu): (1) 15 ppm of Cu from CuSO_4; (2) 30 ppm of Cu from CuSO_4; (3) 15 ppm of Cu from Availa-Cu; and 4) 30 ppm of Cu from Availa-Cu. A fifth treatment provided a single 25 g dose of CuO needles (Bolus) that supplied 20 g of Cu. Mean liver Cu concentration was higher (P<0.01) in heifers receiving Feed-Cu treatments compared to those receiving the bolus. Mean liver and plasma Cu concentrations were higher (P<0.01) when dietary Cu was provided at 30 ppm. Mean ceruloplasmin concentration tended (P=0.06) to be higher in heifers fed Availa-Cu compared with CuSO_4. Mean superoxide dismutase activity was higher (P<0.05) in heifers fed Availa-Cu vs CuSO_4. The overall results indicate that the utilization of Cu from CuSO_4 and Availa-Cu is similar when fed to heifers provided high doses of Zn. Drenching with high doses of Zn did not severely affect the Cu status of Cu sufficient heifers in this study.