1. Research Institute for the Biology of Farm Animals, 18196 Dummerstorf, Germany;
2. Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS, U. K.;
3. Department of Molecular Animal Breeding, Ludwig-Maximilian University, 81377 Munich, Germany; and
4. Departments of Clinical Chemistry and Pathobiochemistry, University of Leipzig, 04103 Leipzig, Germany