1. Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences; Humboldt-Universität zu Berlin; Invalidenstraße 42 Berlin 10115 Germany
2. Department of Animal Production; Faculty of Agriculture; Cairo University; El-Gamma Str. 6 Giza 12613 Egypt
3. Department of Breeding and Genetic Resources; Institute of Farm Animal Genetics; Friedrich-Loeffler-Institut; Neustadt-Mariensee 31535 Germany
4. Lohmann Tierzucht GmbH; Am Seedeich 9-11; 27472 Cuxhaven Germany