1. Centre for Genetic Improvement of Livestock, Department of Animal Biosciences, University of Guelph, Guelph, ON, N1G 2W1, Canada.
2. Department of Animal Science, University of California-Davis, Davis, CA 95616, USA.
3. Department of Agricultural, Food and Nutritional Science/Livestock Gentec, University of Alberta, Edmonton, Alberta, T6G 2R3, Canada.
4. Institute of Genetics, Vetsuisse Faculty, University of Bern, 3012 Bern, Switzerland.