1. Faculty of Veterinary Medicine, Utrecht University, Yalelaan 7, 3584 CL, Utrecht, The Netherlands
2. Research & Development Center, Royal Canin S.A.S., B.P.4, 650 avenue de la Petite Camargue, 30470 Aimargues, France
3. Animal Nutrition Group, Wageningen University, PO Box 338, 6700 AH, Wageningen, The Netherlands