The term genetically modified organism ( GMO) refers to plants, microbes and animals with genes transferred from other species in order to produce certain novel characteristics (for example resistance to pests, or herbicides) and are produced by recombinant DNA technology. Four main sources of hazards of GMO are discussed by scientists worldwide: 1) those due to the new genes, and gene products introduced; 2 ) unintended effects inherent to the technology; 3) interactions between foreign genes and host genes; and 4) those arising from the spread of the introduced genes by ordinary cross-pollination as well as by horizontal gene transfer. GM crops contain material, which is not present in them under natural conditions, and they form a part of our daily diet. To understand what effect they can have on us and on our animals, it is very important to study the influence of those GM plants in different organisms for several generations. At present, these studies are lacking from the scientific literature. Also, several detrimental effects of GM crops had been showed on the metabolism of animals. The hazard of GMO was shown for animals and the environment in many investigations. Earlier it was shown that consumption of GM food by animals led to the negative changes in their organisms. Experiments, conducted by A. Pusztai showed that potatoes modified by the insertion of the gene of snowdrop lectin (雪花莲凝集素 ), stunted the growth of rats, significantly affected some of their vital organs, including the kidneys, thymus (胸腺) , gastrocnemius muscles (腓肠肌) and others and damaged their intestines and their immune system.