The effects of copper deficiency and of copper excess on mature Merino and Border-Leicester ewes were studied experimentally over a period of 3½ years with five evenly matched groups of each breed which were all depastured together as one flock on terrain where sheep develop cobalt and copper deficiency. All were treated with the equivalent of 1 mg. Co/day. Copper was administered thrice weekly in doses which provided for individuals of the respective groups the equivalent of nil, 1, 5, 50 and 100 mg. Cu/day.
All of the individuals that received only cobalt became anaemic; they lost weight and developed marked symptoms of copper deficiency.
The supplement of 1 mg. Cu/day was sufficient to delay the onset of these symptoms, but it failed to increase significantly the concentration of copper in the blood and it was insufficient to ensure normal myelin formation in the central nervous system of lambs born of the ewes which had received this treatment for 2 years prior to mating.