1. New South Wales Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW 2568, Australia
2. New South Wales Department of Primary Industries, Beef Industry Centre, Armidale, NSW 2351, Australia
3. New South Wales Department of Primary Industries, Agricultural Research Centre, Trangie, NSW 2823, Australia
4. Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia