Mating and lambing in an experimental flock of merino sheep

Abstract

Merino ewes, 1278 in all, representing 3 age groups, were pen-mated in 32 lots to individual rams, and a further 200 similar ewes were mated in one lot to 8 rams. The layout of the yards, the techniques employed, and the ration fed to the sheep are described. The reaction by the ewes to the unusual conditions of restraint imposed upon them during both mating and lambing were observed, and it was demonstrated that with care and attention large flocks of Merino sheep are suitable subjects for intense investigations. Data relating to incidence and duration of oestrus, the length of oestrous cycles, and performance of individual rams were recorded in detail for all animals. Extensive information on all aspects of lambing is examined. It was found that the age of the dam, within the range under observation, was associated with lamb losses, birth weight of progeny, and occurrence of multiple births, but was not associated with incidence of oestrus, conception, length of gestation, or sex ratio of progeny. Length of gestation was found to be associated with sex and birth weight of progeny but was not significantly associated with the incidence of single or multiple births.