Safety and effectiveness of cupric oxide particles for increasing liver copper stores in cattle.

Five groups of three or four crossbred steers, mean initial liveweight 220 kg, were given a diet of barley and hay ad libitum. Each animal received a single oral dose of 0, 5, 10, 20 or 40 g cupric oxide particles. A dose of 5 g cupric oxide particles increased liver copper stores for about 240 days and higher doses increased liver stores for longer but 40 g was no more effective than 20 g (85 mg kg-1 liveweight). Variation among individuals was marked but the highest liver copper concentration recorded (7.59 mmol kg-1 dry matter) produced no biochemical evidence of copper toxicity. Earlier, cupric oxide particles were separated into three fractions, clumps, short rods and long rods and 5 mg kg-1 liveweight of each fraction given to steers of 173 kg mean liveweight. The form of the particles did not affect either their retention in the alimentary tract or the accumulation of copper in the liver.