Blood Copper-levels in Sheep in Relation to Genetic Factors, Parity and Previous Swayback History

Abstract

BLOOD copper-levels are known to be associated with the incidence of swayback in lambs (see Barlow et al.)¹. A sample of fifty-five ewes was bled some 6 weeks prior to lambing and almost a year after a 15 per cent incidence of swayback had occurred among the lambs in the flock from which these ewes were drawn. The flock consists of three breeds (Scottish Blackface, South Country Cheviot and Welsh Mountain) and the crosses between these breeds. The ewes belong to two breeding classes, outbred (F₂) and 25 per cent inbred (I₁), and to four parities. The choice of animals for bleeding took account of these subdivisions within this flock and of swayback history of the lambs born to ewes of parity 2 and more in 1964. Blood copper values were estimated by the method of Butler and Newman².