1. NSW Department of Primary Industries, Livestock Industries Centre, University of New England, Armidale, NSW 2351, Australia
2. CSIRO Agriculture and Food, FD McMaster Laboratory, Armidale, NSW 2350, Australia
3. School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia
4. NSW Department of Primary Industries, Tamworth Agricultural Institute, Calala, NSW 2340, Australia