Reproductive performance of the Thoka Cheviot sheep

Abstract

The Thoka gene for fecundity, a gene which originally occurred in Icelandic sheep, was introduced to the UK in 1985 and through a programme of crossbreeding was established in Cheviot sheep (Russel et al, 1997). Ewes are now retained as "Thoka carriers" only if they have lambed in each of the first three years and had at least two sets of twins. The gene has been introduced into separate North and South Country Cheviot (NCC and SCC) lines which are now phenotypically indistinguishable from purebred animals and contain proportionately less that 0.2 of the Icelandic genotype. The purpose of this analysis was to determine the increase in fecundity in the two breeds and whether or not the reproductive response to the incorporation of the Thoka gene differs between NCC and SCC breed types.