1. Centre for Nutrition Modelling, Department of Animal & Poultry Science, University of Guelph, 50 Stone Road East, Guelph, ON, Canada N1G 2W1
2. The Iams Company, Mason, OH 45040, USA
3. Instituto de Ganadería de Montaña (CSIC-ULE), Departamento de Producción Animal, Universidad de León, 24071 León, Spain