1. Department of Animal Physiology and Biostructure; Faculty of Veterinary Medicine; University of Environmental and Life Sciences in Wroclaw; Kozuchowska 1/3 51-631 Wroclaw Poland
2. Department of Morphological Sciences; Faculty of Veterinary Medicine; Warsaw University of Life Sciences; 159 Nowoursynowska 02-776 Warsaw Poland
3. Division of Poultry Breeding; Institute of Animal Breeding; University of Environmental and Life Sciences in Wroclaw; Chelmonskiego 38a 51-631 Wroclaw Poland