Copper status of ewes fed increasing amounts of copper from copper sulfateor copper proteinate

The Cu status of mature, crossbred ewes fed two sources (CuSO4 vs Cu protei nate) and three levels (10, 20, or 30 mg/kg) of dietary Cu was determined i n a 73-d feeding trial. Ewes (n = 30) were fed a basal diet containing rice meal feed, cottonseed hulls, cottonseed meal, meat and bone meal, cracked corn, and vitamin-mineral supplements at 2.5% of BW to meet NRC requirement s for protein, energy, macrominerals, and microminerals, excluding Cu. The basal diet contained 5 mg/kg Cu, 113 mg/kg Fe, .1 mg/kg Mo, and .17% S. Cop per sulfate or Cu proteinate was added to the basal diet to supply 10, 20, or 30 mg/kg of dietary copper in a 2 x 3 factorial arrangement of treatment s. Ewes were housed in 3.7- x 9.1-m pens in an open-sided barn. Blood sampl es were collected on d 28 and 73. Ewes were slaughtered on d 74, and liver and other tissues were collected to determine Cu concentrations. An interac tion (P =.08) occurred between source and level for liver Cu, The interacti on existed due to an increase in liver Cu concentrations when ewes were fed increasing dietary Cu from CuSO4 but not when fed Cu proteinate diets. The re was no source x level interaction (P >.10) for the blood constituents me asured. On d 73, plasma ceruloplasmin activity was greater (P <.05) in ewes fed Cu proteinate than in those fed CuSO4 (33.1 vs 26.8 mu M.min(-1).L-1). Increasing the concentration of dietary Cu did not affect(P >.10) plasma c eruloplasmin. Packed cell volume (PCV), red blood cell count (RBC), white b lood cell count, whole blood hemoglobin (wHb), plasma hemoglobin, and plasm a Cu were similar between sources of Cu. Ewes fed 20 mg/kg Cu had lower (P <.05) PCV, RBC, and wHb than those fed 10 or 30 mg/kg Cu diets. Feeding up to 30 mg/kg Cu from these sources did not cause an observable Cu toxicity d uring the 73-d period.