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Over the past two decades, many approaches for transferring genes into the genome ofdomestic animals have been devised. The main purposes of transgenesis are: to increaseanimal capabilities, to knock down or silence both onco-genes and deleterious genes, and toproduce a pharmaceutical protein. Transgenesis techniques include pronuclear microinjection(PNM), somatic cell nuclear transfer (SCNT), viral infection (VI) and sperm-mediatedgene transfer (SMGT). The first transgenic mouse was produced by using the PNM techniqueand transgenic animals from other species (rabbit, sheep, pig and cattle) have beenproduced thereafter. However, the PMN technique had certain drawbacks: low efficiency,random integration site of the transgene and a high mosaic rate. For this reason, other alternativetechniques have been devised to overcome its drawbacks. The most reliable methodfor transgenesis which bypasses mosaics is SCNT. However, this method is complicated andtedious; with multiple stages that need setting up. VI has been used to transfer genes into theoocytes and zygotes with high efficiency and versatility. In spite of its simplicity, the maximumtransgene length should be less than 8.5 kb. Currently, spermatozoa are considered as analternative method of carrying transgenes into the oocytes with minimum technical demands.In contrast to VI, SMGT is being used successfully to transfer different kinds of BACs withmore than 200 kbp into mouse oocytes. The present review summarizes the methods bywhich transgenes can be introduced into zygotes of domestic animals.