The link between mid-pregnancy shearing in Merino ewes and improved lamb survival.

Metcalfe, Brodie
Murdoch University


The project will be undertaken at the DPIRD Katanning Research Facility on ewes from the MLA Genetic Resource Flock providing direct engagement with industry funding bodies and a fully functional Department sheep enterprise.

Traditionally, the majority of all sheep in Western Australia are shorn in spring after lambing. The timing of shearing is largely driven by the availability of shearers and the mitigation of the flystrike risk over summer. With a growing number of producers opting to shear sheep every six to eight months to meet market specifications, shearing now frequently coincides with mid pregnancy. Mid-pregnancy is when the foetus is undergoing developmental changes that are crucial to peri-parturient survival such as the proliferation of brown adipose tissue to be used as an energy source after birth. Mid-pregnancy shearing is associated with a short terms stress due to shearing, as well as a longer term stress caused by the loss of insulation and increased exposure of the ewe. There is substantial evidence, mainly from the UK and NZ, that mid-pregnancy shearing and the associated stress during the colder autumn/winter months is associated with improvements in foetal growth and development, leading to increases in birth weights of multiple-born lambs and improved survival to weaning. These improvements have never been investigated or quantified in Merinos, the predominant sheep breed in Western Australia, to determine the potential improvement to lamb survival and thus welfare.

To investigate the impact of mid-pregnancy shearing in Merino ewes on lamb survival, 200 pregnant Merino ewes will be selected and half will be shorn during mid-pregnancy. Ewes will lamb on 1Ha plots (12 ewes per plot) where ewes are stratified by shearing, weight, body condition and number of lambs (single, twin). During lambing, survival behaviours (e.g. time to stand and suckle) will be observed and birthweight will be recorded. Growth rate and survival to weaning will be recorded.