1. Faculty of Agrobiology, Food and Natural Resources , Czech University of Life Sciences Prague , Kamýcká 129, 165 00 Prague, Czech Republic
2. Institute of Animal Physiology and Genetics, Academy of Sciences of the Czech Republic , Rumburská 89, 277 21 Liběchov, Czech Republic
3. Department of Nutrition, Genetics and Ethology, Faculty of Veterinary Medicine , Ghent University , Heidestraat 19, 9820 Merelbeke , Belgium