Cryopreseravtion of gametes, embryos or DNA segments can be quite an effective and safe approach for breeds or strains whose populations are too small to be conserved by any other means. The safety of these methods was demonstrated by background irradiation studies. For example, studies based on irradiation of mouse embryos exposed to the equivalent of hundreds of years of background mutation showed no detectable damage.
Regeneration of offspring following transfer of frozen-thawed embryos was successful for all major domestic species, except the buffalo. In the cattle, transfer of frozen-thawed embryos is now a commercial practice and embryo survival rate after thawing can be as high as 80% with a pregnancy rate of about 50%. Cryopreseravtion of oocytes followed by successful fertilisation and live births was achieved in the mouse. Cryopreserved bovine oocytes were successfully matured and fertilised in vitro and zygotes developed to blastocyst stage. These trends strongly suggested that long-term cryopreseravtion of mammalian oocytes is possible. Pregnancy rates of 50-60 % for fresh and frozen-thawed in vitro produced embryos were reported from advanced laboratories. Also, calves were produced from transfer of both split and frozen-thawed in vitro produced embryos in India also. Development in genetic engineering, cryobiology, cell biology and embryology will provide techniques that may enhance our ability to preserve germplasm in vitro. Techniques such as transfer of DNA within and between species and the production of viable transgenic animals are far from practical application. However, biotechnology will certainly contribute newer and cheaper methods for preservation such as storage of catalogued DNA. At present, other than live animal and embryo preservation, the other techniques do not allow preservation of genomes in a form which can be or gene combinations for possible future regeneration.
Conservation of indigenous animal genetic resources should be one of the priority livestock development activities for India. The critical importance of these resources to their owners in developing countries need not be re-emphasized. Their importance to developed countries is also becoming evident as indicated by the increasing importation of tropical germplasm by these countries. It is highly likely that these resources will become of increasing importance to the industrialised countries either as sources of unique genes or when environmental concerns necessitate change in production systems. Technology for cryopreseravtion of semen and embryo is sufficiently developed to be applied in India. There is also a strong case for support of animal genetic resources conservation. Currently, transgenic animals are being developed for drug production. For this purpose, small herds of transgenic animals are likely to be sufficient to produce sufficient quantities of high-value products, such as pharmaceuticals. The impact of transgenic animals on animal breeding will also be limited in the short term as the propagation process of a transgene in a population is relatively slow. The development of transgenic animals will increasingly and most appropriately be driven by the information base being generated by the genomic research.
Despite the present low efficiency and the high cost of the technology, cloning technology could have an impact on the conservation of animal genetic resources as it offers a way to preserve and propagate breeds and or species at risk.
Strategies for conservation and sustainable management
The main considerations will guide future activities:
1. Cataloging all the available genetic diversity in AnGR.
2. The conservation of a critical amount of animal genetic resources.
3. The maintenance of diversity in situ as well as ex situ.
4. Improvement in rate and efficiency of livestock production. It will inevitably lead to changes in both the genetic composition of livestock population and the relative importance of different breeds.
5. Effective generation of increased output per unit of input from the livestock sector while preventing major loss in animal genetic resources.
6. Invention of new value added livestock products for utility at global level.
7. Increased levels of organic livestock farming
8. Preventing environmental degradation.