1. Institute for Agricultural and Fisheries Research (ILVO), Technology and Food Science Unit, Brusselsesteenweg 370, 9090 Melle, Belgium
2. Department of Biochemistry, Physiology and Microbiology, Laboratory for Zoophysiology, Ghent University, Krijgslaan 281 (S33), B-9000 Gent, Belgium
3. Faculty of Veterinary Medicine, Laboratory of Chemical Analysis, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium