1. Laboratory of Animal Nutrition and Animal Product Quality, Department of Animal Production, Faculty of Bioscience Engineering, Ghent University, Proefhoevestraat 10, 9090 Melle, Belgium, Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure 653, 9000 Ghent, Belgium, and Laboratory of Food Analysis, Faculty of Pharmaceutical Sciences, Ghent University, Harelbekestraat 72, 9000 Ghent, Belgium