反刍家畜的牙齿很特殊。The teeth of ruminant animals are specialised.纯种家畜的养育者们为了保持纯正的动物血统无休止地制造遗传上的混乱现象.Breeders of thoroughbred animals perpetuate genetic disorders to keep pedigrees pure.1900年也开始了家畜的血型研究.Investigations into the bl...