Copper oxide needles for cattle: a comparison with parenteral treatment.

Two trials of oral copper oxide needles for cattle are described. In one, a dose of 13.0 g copper oxide/100 kg liveweight in yearling bullocks was compared with parenteral copper at a total dose rate of 400 mg copper. In the second, three oral dose rates (3.5, 7.0 and 10.5 g copper oxide/100 kg liveweight) in calves were compared over two years with a total dose of 500 mg parenteral copper. In both trials liver copper values reached a peak at about six weeks after oral dosing and in the second trial the peak was dose related. Thereafter liver levels declined in all the oral treatment groups; normal levels of more than 30 mg/kg liver dry matter were maintained for 30 weeks in the first trial and for 40 to 47 weeks, depending on dose rate, in the second. In both trials repeated parenteral treatments were required to maintain liver levels within the normal range. The results support earlier findings that an adequate dose of copper oxide needles can maintain the copper status of cattle for periods of at least six months.

Accumulation of copper on albumin in bovine plasma in vivo after intravenous trithiomolybdate administration.

The initial disappearance of intravenously administered copper (10 to 20 mg) from bovine plasma in vivo was delayed by the intravenous injection of trithiomolybdate (20 to 75 mg molybdenum per 400 to 445 kg steer); however, the most characteristic effect was the retention of up to about 0.5 mg copper per litre plasma for up to 24 hours after injection. Sephadex G-100 gel filtration of plasma samples showed that this retained copper was associated with the albumin fraction. The effect of trithiomolybdate was very dependent upon the interval between the injections of trithiomolybdate and copper. It is suggested that this variability was due to thiomolybdate metabolism. The infusion of trithiomolybdate (12 to 75 mg molybdenum) over 24 hours also caused the accumulation of albumin-bound copper. The amount bound did not exceed approximately 0.5 mg copper per litre plasma even when the diet of the steers was supplemented with copper sulphate or when copper sulphate (2 X 15 mg copper) was injected directly during the infusion. It is suggested that the longer term effects of trithiomolybdate are not merely a consequence of a simple copper-thiomolybdate reaction but result from three-way interactions between trithiomolybdate, albumin and copper, and that slow infusion of trithiomolybdate provides a model for the study of the systemic effects of dietary molybdenum in cattle.