1. Department of Agricultural Economics and Rural Development, University of Goettingen, 37073 Goettingen, Germany
2. Department of Animal Sciences, University of Goettingen, 37075 Goettingen, Germany
3. Institute of Animal Nutrition, Friedrich-Loeffler-Institut, 38116 Braunschweig, Germany
4. Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, 31535 Neustadt, Germany
5. Center for Integrated Breeding Research, University of Goettingen, 37075 Goettingen, Germany