Application of biotechnology for reproductive manipulation

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For the efficient increase in the number of farm animals and for the improvement of amounts and quality of animal products such as wool, meat and milk, biotechnological new techniques of animal production have been developed and practically applied specifically concerning on the following subjects : (1). Artificial insemination (AI) is not a new technique, but the technique itself has been dramatically improved year by year and an epoch-making technique, deep freezing of semen was devised during the year, 1948-1950 by Dr. Paige and co-workers". The successful deep freezing of semen was made it possible to use widely the excellent male animals especially in cattle. ( 2 ) . The technique of embryo transfer (ET) has been applied effectively for wide use of genetically excellent cows. About 410 thousands of embryos (210, 000 fresh and 200, 000 frozen embryos) were transferred annually in cattle throughout the world. ( 3 ). Producing identical animals is important for the following reasons ; a). Identical animals are valuable as experimental animals because of their genetic identity, b) . the number of genetically excellent animals can be rapidly increased. More recently production of identical animals by nuclear transplantation, cloning has been in progress for the practical application in cattle breeding. ( 4 ) . Sex control of offspring has been carried out by two different methods, one is the separation of X- and Y- bearing spermatozoa and the other is the sexing of embryos before transfer. ( 5 ) . Main purpose of in vitro fertilization (IVF) in mammals was to investigate the gamete interaction in the process of fertilization. In case of cattle IVF, the technique was applied to the practical cattle production about 10 years after the first successful report of IVF. ( 6 ). Originally the purpose of IVF by assisted micromanipulation of gametes was to investigate the interaction of gametes at the site of sperm penetration from the physiological view point. This technique has been clinically applied for the therapy of male factor infertility. ( 7 ) . Transgenesis in domestic animals briefly referred here is one of the important subjects at present and in future.

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