1. Animal Nutrition Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands
2. Laboratory of Food Chemistry, Wageningen University, P.O. Box 17, 6700 AA Wageningen, The Netherlands
3. Division of Nutrition, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80152, 3508 TD Utrecht, The Netherlands