1. Department of Animal Biosciences and Campbell Centre for the Study of Animal Welfare, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada
2. Department of Animal Science, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA
3. Department of Animal Science, Michigan State University, 474 S. Shaw Lane, East Lansing, MI 48824, USA
4. Department of Animal and Avian Science, University of Maryland, College Park, Building 142, College Park, MD 20742, USA