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反芻家畜的牙齒很特殊。The teeth of ruminant animals are specialised.純種家畜的養(yǎng)育者們?yōu)榱吮３旨冋膭游镅y(tǒng)無休止地制造遺傳上的混亂現(xiàn)象.Breeders of thoroughbred animals perpetuate genetic disorders to keep pedigrees pure.1900年也開始了家畜的血型研究.Investigations into the bl...