作者单位:Institute for Animal Breeding and Genetics of Domestic Animals, University of Giessen, Giessen, Germany[1]GFS Ascheberg, Ascheberg, Germany[2]Unit for Reproductive Medicine of Clinics/Clinic for Pigs and Small Ruminants, University of Veterinary Medicine Hannover Foundation, Bünteweg 15, D-30559 Hannover, Germany[3]