New animal breeding techniques and their application.

The new biotechnologies of gene transfer, in-vitro production, cloning and sexing of embryos have been developed and are being refined with efficiencies suitable for use in animal agriculture. Efficient in-vitro systems for maturing oocytes and capacitating spermatozoa, for fertilizing and developing the embryos have resulted in commercial in-vitro production of embryos. Cloning of embryos by nuclear transfer has been accomplished for sheep, cattle, pigs and rabbits with nuclear material supplied by embryos as late as the 120-cell stage in sheep. Embryos have been recloned but much research is needed to increase the efficiency of this procedure. Research is needed to develop the use of cultured cells in embryo cloning so that the number of clones may be increased to thousands or millions. Embryos of most species can be sexed in a non-damaging way with male specific antibodies and a more efficient method, amplified DNA hybridization, is beginning to be tested commercially. Transgenic embryos or offspring have been produced for mice, rats, rabbits, chickens, fish, sheep, pigs and cattle. Genes can be targeted for expression in specific tissues but more efficient methods and a better understanding of the genes to be transferred as well as control by man of the time and tissue of specific gene expression are needed. Before many transgenic animals of value can be made, we must know which genes to introduce. Presently there is a poor understanding of the genes influencing animal growth, efficiency of growth, environmental adaptation, meat, milk or egg composition or animal disease resistance. Their identification will come from badly needed efforts to map the genome of domestic animals. These and other new technologies promise to change livestock breeding drastically in the next decade.