A comparison of the performance of single and twin born Corriedale ewes and lambs

Abstract

Reproductive performance of Corriedale sheep from the experimental farm at Mount Derrimut, Victoria, was studied over five years (1 968 to 1972) in a flock selected for the production of medium wool and the ability to produce twins. Traits measured included fertility at mating, lambing rate, twinning rate, mortality at birth and interval between mating and lambing. Ewes born as twins were less fertile at first mating, improved rapidly in their reproductive performance at subsequent matings, but then declined in fertility quite early in their breeding life. Twin lambs had a mortality rate at birth nearly three times that of singles, were lighter at birth, grew slowly up to weaning and produced less wool at weaning. Female lambs conceived as co-twins with male lambs tended to be disadvantaged in heir pre-natal development which could be due to an enhancement effect exhibited by the male co-twin.