Mechanism of conserving cattle genetic resources

Once genetic resources have been identified and characterized, two basic conservation activities can be followed, i.e., in situ conservation and ex situ conservation.

In situ conservation:

It requires establishment of live animal breeding farms and their maintenance. The generation and loss of alleles is a dynamic process that should be maintained at close equilibrium through sound management. 

In situ conservation strategies emphasize wise use of indigenous cattle genetic resources by establishing and implementing breeding goals and strategies for animal sustainable production systems.

Information for animal recording and breeding is well established in developed countries through breeding associations which zealously protect the interest of breeds including rare ones. Infrastructure appropriate to systems in developing countries remains scarce.

Advantages of in-situ conservation

• Live animals can be evaluated and improved over the years. Genetic defects can be detected and eliminated. Live animals are always available for immediate use. The animals are gene banks for future use. The herd may have some economic advantages (heat tolerance, disease resistance) which can be exploited and so render the enterprise economically viable. 

• The produce from live animals partly compensates the expenditure, if not entirely. 

• From aesthetic point of view, the live animals are, visible, a pleasure to look at, the people are delighted to see variety of animals and have some cultural value.

Limitations

• The major limitation of live animal conservation is the number of animals that could be maintained. While fixing the number for preservation of a breed, the cost of maintenance, availability of animals and rate of inbreeding should be taken into consideration.  With small population size, the effective population size decreases and the genetic structure of the population is affected due to inbreeding and random drift. 

• Many models are now available which reduce inbreeding to a minimum, but random drift over long periods may lead to a population very different in genetic composition from the initial one. Gene X environment interactions is another disadvantage. 

• In situ conservation involves a large infrastructure of land, buildings, feed and fodder resources, water supply, labour , technical and supervisory manpower, etc. 

• Therefore, new establishments for in-situ conservation of farm cattle genetic resources are quite costly and even the maintenance of existing ones is cumbersome. The costs need to be estimated for each ecosystem.

New technologies

Major changes in livestock production have occurred during the past few decades due to the introduction of several new technologies. 

Examples: Eradication of Rinderpest, artificial incubation, embryo transfer and associated technologies (genomics, cloning and Trangenesis). 

It is therefore necessary that research in newer biotechnologies is intensified, so that traditional genetic improvement methods like progeny testing and sire/dam evaluation schemes are by- passed in future.

Ex-situ conservation:

Ex-situ conservation includes cryogenic preservation. It is the storage of genetic resources, which the farmers are currently not interested in using. 

Ex situ conservation is based on the use of live animals' populations wherever practicable, supported by cryopreservation where technology exists or can be developed, combining within-country gene banks with global repositories. 

Interested governments, non- governmental organizations, research institutions and private enterprises should be encouraged to maintain in vivo samples of breeds at risk, with national inventories being established and kept up to date so that the genetic resources are readily available for use and study. 

Because of random drift and possible gene by environment interactions, ex situ methods are generally preferred over in situ. Ex situ conservation is comparatively more convenient, economical and easy with the application of modern reproductive technologies.

Advantages

• If the preservation is to maintain populations without genetic change, it can be best done by cryogenic storage as it is difficult to breed many generations of animals without any change in the genetic structure. 

• The resources requirement for in situ preservation is quite large as compared to cryogenic methods.

Limitations

• Ex situ preservation using frozen semen delays the restoration of a breed as it can be restored in the future only by upgrading. But this could be overcome through preservation of embryos. 

• Another important factor is the danger faced by a breed restored from cryogenic preservation from important changes in the environment like germs, climate, etc., that have taken place over the years. 

• Variability in cryogenic storage of germplasm, accessibility to their physical location, ownership, behaviour of animal, response of germplasm to freezing and thawing techniques, and poor conception rate.

Ex situ/Cryogenic preservation includes:

• Preservation of frozen semen
• Preservation of oocytes
• Preservation of embryos
• Preservation of ovaries
• Use of embryonic stem cells or blastomeres
• Production of chimeras
• Production of embryos in vitro
• Embryo splitting
• Transgenesis
• DNA libraries