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transfer of value at the commercial level. Research continues on sexing of spermatozoa but it has so far been without success despite many years of effort. If it is eventually successful, then, combined with ET, it will contribute effectively to yet further progress.
34.
Major gains may also be obtained through mastering the maturing and fertilizing of mammalian ova in in vitro conditions. The embryos obtained in vitro maturation and fertilization have been transferred in recipient cows or deep frozen. This in vitro method could be used to provide a cheap supply of embryos for developing countries. Further, cloning of embryos could well bring about a revolution in animal reproduction, but a lot more research is called for.
35.
Regarding gene transfer, the most important breakthrough for genetic engineering with mammals in the near future will be in improving methods of transfer of DNA. So far, in pigs, sheep and goats, numbers of embryos surviving gene injection procedures are below 10 percent, and numbers of transgenic offspring compared to number of embryos transferred are less than 1 percent.
36.
As regards manipulation of rumen microflora, it seems possible to construct rumen bacteria with greater amylase and xylase activity to break down starch and hemicellulose. Regulation through genetic engineering, of such bacterial functions as breakdown and synthesis of protein of feed, increased hemicellulose breakdown and above all the possibility of the breakdown of plant lignin, not so far done by any animal, is very complex. The genetic engineering of microflora opens up enormous possibilities for the regulation of fermentation processes in the rumen. But, little is known so far of the complicated enzymatic relationships in the rumen which are influenced by hundreds of bacterial species. Even less is known of the genetics of these bacteria. Work in this field is of extreme importance for developing countries.
37.
Regarding vaccine production, genetically engineered vaccines. promise a higher grade of innocuity, efficiency, and a lower cost of production. Promising results of veterinary research in the preparation of sub-unit vaccines for veterinary use, vaccines based on peptide chemistry and live attenuated vaccines have been achieved. DNA recombinant techniques, expressed antigens, synthetic peptides, monoclonal antibodies and some other biotechnology procedures and products are opening up a new future for the animal health immunization programme. There are encouraging examples from this Region that this type of research can be carried on in developing countries as well.
38.
Growth hormones play a central role in regulating growth and milk production. Although the powerful effect of these hormones were known since the 1930s, production of these chemicals in quantities large enough to be applicable commercially has been made possible only by genetic engineering. The new hormones will lead to dramatic production spurts, reshaping their respective industries. Recent reports indicate that administration of recombinantly derived bovine growth hormone (bGH) brings about remarkable increases in milk production by the cows and buffaloes.
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