1. INRA, UMR1348 PEGASE, F-35590 Saint-Gilles, France
2. Agrocampus Ouest, UMR1348 PEGASE, F-35000 Rennes, France
3. Nutreco R & D, 5832 AE Boxmeer, The Netherlands
4. Agriculture and Agri-Food Canada, Dairy and Swine R & D Centre, Sherbrooke, Quebec J1M 0C8, Canada