CHALLENGES AND OPPORTUNITIES FOR INTEGRATING GENETICALLY-MODIFIED ANIMALS INTO TRADITIONAL ANIMAL BREEDING PLANS

Techniques have been developed to introduce specific genes from one sp ecies into the germplasm of another, including livestock. This paper r eviews reports on evaluation, selection, and breeding procedures for i ntroduction and multiplication of transgenes in breeding populations o f livestock. Before transgenes are introduced and multiplied in commer cial breeding populations, it is necessary to test transgenics extensi vely for both favorable and unfavorable transgene effects. Parent stoc k used to produce transgenic founder animals should be selected to exc el in polygenic breeding value for economically important traits, espe cially if founder animals or their sons are to be used directly by AI in commercial populations. However, polygenic breeding value of founde r transgenic animals and inbreeding depression are of negligible impor tance if a transgene is introgressed into a selection nucleus populati on from three or four generations of backcrossing. Transgenic developm ent should be economically viable for traits with major effects on net merit, especially in the dairy industry, where transgenic sires can b e used extensively by AI. A minimum effect of about 10% of the mean (o r one phenotypic standard deviation) is a reasonable approximation of the minimum transgene effect that would be necessary to justify introg ression into a nucleus swine population. A transgene effect of 10 to 2 0% of the mean would be required for most economic traits in beef catt le.