H. Fagari-Nobijari - Department of Animal Science, Faculty of Agriculture, Zanjan University, Zanjan, Islamic Republic of Iran.
H. Amanlou - Department of Animal Science, Faculty of Agriculture, Zanjan University, Zanjan, Islamic Republic of Iran.
M. Dehghan-Banadaky - Department of Animal Science, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Islamic Republic of Iran.

This study was performed to determine the effect of copper on growth performance, blood metabolites and claw health in young Holstein bulls in a humid area in north of Iran. One hundred and two young Holstein bulls (Initial body weight= ۳۷۷.۳±۱۷.۱ kg) were randomly allocated to two treatments in a completely randomized design for ۵۶ days. The treatment groups received: (۱) the basal diet of no supplemental Cu (control; n= ۵۰); (۲) basal diet plus ۳۰ mg of Cu kg-۱ of Dry Matter (DM) as CuSO۴ (n= ۵۲). Animals received fresh total mixed ration for ad libitum feeding allowing ۱۰% refusals. The groups’ Dry Matter Intake (DMI) was assessed daily. The Body Weights (BW) were recorded and jugular blood samples collected on days ۰, ۲۸ and ۵۶. All claws of young bulls were examined every two weeks for an identification of claw lesions. Copper supplementation improved Average Daily Gain (ADG) and gain:feed (G:F;P < ۰.۰۵). Serum cholesterol decreased with Cu supplementation (P< ۰.۰۰۱). Serum Zn, Cu, and urea N were not affected by supplementation of Cu; however, plasma total protein (P< ۰.۰۰۱), and albumin (P< ۰.۰۰۱) were increased by a supplementation of Cu. The prevalence of lameness was ۱۹.۶% and control group had the highest Odds ratio (OR= ۲.۴۳). As a result, it is concluded that supplemental Cu might improve growth performance in the finishing bulls and decrease the prevalence of lameness.

Blood metabolite, Claw health, Copper, Young bull