How does maternal genetic merit and country of origin impact lamb performance pre- and post-weaning?

•High Irish lambs grew faster from birth to drafting compared to Low Irish lambs.•New Zealand lambs were drafted earlier compared to Low Irish lambs.•High genetic merit lambs, regardless of country of origin, outperformed Low Irish lambs.•New Zealand genetics are suitable for use within an Irish production system.•Selecting animals on maternal genetic merit improves lamb performance.