1. a Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry , Dörnbergstrasse 25–27, D-29223 Celle , Germany
2. b Leibniz Institute for Farm Animal Biology, FBN Dummerstorf Wilhelm-Stahl-Allee , D-18196 Dummerstorf , Germany
3. c Department of Biomedical Sciences, Biochemistry University of Veterinary Medicine Vienna Veterinärplatz , A-1210 Vienna , Austria
4. d Swedish University of Agricultural Sciences, Dept. of Animal Nutrition and Management Kungsaengen Research Centre , S-75323 Uppsala , Sweden