Copper deficiency: a study of prophylaxis and the interaction with cobalt therapy in lambs on improved hill pastures

Abstract

An experiment was conducted with 84 suckling Scottish Blackface twin lambs on an improved hill pasture with a history of cobalt deficiency and molybdenum/sulphur-induced copper deficiency. The dams of 13 pairs of twins were treated with 90 mg copper at parturition (Cue) and one member of each pair was given a cobalt bullet (Co + ). One member of each of a further 29 pairs was treated periodically with 5 to 15mg copper to maintain plasma copper concentrations >0·6mg/l (Cu+) while their siblings received no supplementary copper (Cu). Fourteen of these pairs also received a cobalt bullet (Co + ). Lambs not treated with cobalt are designated Co−.

The Cu^e treatment increased milk copper concentrations, but only for a short time, and resulted in transitory increases in lamb plasma copper concentrations and rate of live-weight gain. At the end of the grazing phase, at approximately 20 weeks of age, Cu⁺ lambs had gained 0-28 kg more weight than Cue lambs and 158 kg more than Cu^e lambs, and had higher liver copper concentrations. Cu⁺ and Cu^e lambs had heavier and fatter empty bodies and carcasses than Cu^{− lambs. The cobalt treatment produced no effects at this stage.}

Fifty-four of the lambs were housed and given dried grass pellets ad libitum. After 83 days liver copper concentrations were higher in Co⁻ than Co⁺ lambs, and in Cu⁺ than in Cu⁻ and Cue lambs. The copper treatments had no effect on rate or efficiency of live-weight gain, but Co⁻ lambs gained weight more quickly and more efficiently than Co+ lambs.