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Phenotypic characteristics (appearance) are often used to divide animals into species, and there is great diversity across species. However there may be limited genetic variation within any given species. Domestication of animals has led to the development of specific breeds, in the process increasing the within species variation.
Intensification of Agriculture
As agriculture has moved from small production systems to large commercial systems farm animal genetic diversity has declined. Selection goals and production environments are now very similar throughout the developed world. We are very efficient at changing the genetic diversity of populations.
The result? Modern animal industry now uses only a few breeds of any species. Of the many breeds once commonly seen on farms, many have declined greatly in numbers and others have disappeared completely.
Reasons for Genetic Conservation
If we have the best why are we concerned about preserving genetic diversity?
We need to keep potentially
useful genes and gene combinations
The ‘best’ is defined by industrial production of a small number of products in a developed world. We are only now beginning to understand the complexity of genes and how they interact to produce the phenotype. We risk losing genes of value.
To take advantage of heterosis
Heterosis is the increase above the average of the parent stocks obtained by crossing genetically diverse breeds. Crossbreeding is practiced widely in swine, sheep, and beef production. If only a few breeds are kept the opportunity to develop good crosses is lost.
To overcome selection plateaus
A selection plateau occurs when genetic variation is lost; no further change is possible because animals are genetically alike. If genetic variation exists in other breeds, crosses can be made to overcome this.
To provide an insurance policy against
For cultural reasons
Our history is closely linked to agricultural practices and use of particular breeds. The vache Canadienne and the poule Chantecler are associated with French Canadian culture. The Newfoundland pony developed in response to a harsh environment and is now recognized as a Heritage breed by Newfoundland and Labrador. The Canadian horse has been recently recognized by Parliament as the national horse of Canada. Poultry breeds such as the Barred Plymouth Rock and heavy horse breeds such as the Percheron and Clydesdale were common on farms. These breeds are now used on ‘living history’ parks or ‘living museums’, both important in education and tourism.
Control (unselected) lines are used to measure genetic progress in selection. Identification of specific genes, which regulate traits such as product quality and health, is made easier by comparing very different groups.
Economic evaluation of breeding programs now includes sociological aspects, as part of a focus on sustainable rural development. Research into the role of minor breeds in such production systems is needed.
Goals of conservation
To keep genetic variation as gene combinations, in a form that is easily recovered
Live animals may be appropriate for some situations. Cryopreservation of sperm, ova or embryos is possible in many species and new tissue culture technologies show promise.
To keep specific genes
As gene sequences linked to specific traits are identified and defined we will be able to save those DNA portions of interest.
Steps necessary for conservation
Definition of a breed as endangered depends on factors such as the number of breeding males and females, overall numbers, number of sub-populations, and trends in population size. It is thus important to monitor numbers and change in numbers on an on-going basis.
Stocks must be characterized for phenotype and genotype, using new technology as appropriate. Gene mapping approaches such as testing for single nucleotide polymorphisms (SNP’s) help to track ancestry and to determine the genetic distance of one group from another. Phenotypic performance evaluation must be standardized, and carried out in the environment in which the stocks might be used.
Choice of breeds for conservation must include cultural reasons, potential value and threat of extinction. New mathematical techniques and economic theories assist in assessing risk of loss and potential benefits.
Saving pure breeds preserves that breed’s characteristics and makes a readily identifiable animal. Crossing several breeds to produce composites has the advantage of saving the genetic material from all while reducing upkeep costs. However the total genotype of each breed is lost.
Populations can be saved as live animals. This is expensive and unless the breed can be used for production is not likely to succeed. Development of niche marketing schemes emphasizing the traits of a particular breed can be successful. Linking breed maintenance with tourism and education (farm visits) can be useful.
Cryopreservation: Semen, ova, and preferably embryos can be frozen. This is successful for cattle, but is unfortunately difficult for some species. For those species where cryopreservation is routinely practiced a national centre for monitoring and maintaining frozen genetic resources is needed.
DNA collection: The potential exists to use DNA and cloning to re-develop breeds, but the technology is still new and costs are high. Whether kept as live animals or as frozen material, more than one location is needed. Natural disasters, accidents, and changes in financial resources can result in instant loss of a stock.
Who is involved?
Commercial animal industry
The commercial industry must emphasize traits of economic value now and in the short-term future. Industrial breeders keep genetic stocks as necessary to satisfy that need. Increased globalization and vertical integration of companies puts such genetic reserves at risk in Canada and around the world.
Private producers keep stocks of minor breeds, as a hobby or as part of a farm enterprise. Emphasis may be on phenotype and small populations may lead to reduced genetic diversity. Stocks are subject to loss as a producer’s situation changes.
The Canadian Farm Animal Genetic Resources Foundation works with government, universities and research centers, rare breed organizations, and private producers to obtain funding and provide resources and information on conservation of animal genetic resources. Membership includes farmers, scientists, breed associations and commodity organizations.
Rare Breeds Canada is an organization of producers and others interested in conservation of minor breeds of livestock. Information on management methods, breeds at risk, and exchange of genetic material is facilitated through meetings, a newsletter and a web site. The group works closely with other national groups such as the American Livestock Breeds Conservancy. Rare Breeds International is the umbrella organization for these groups around the world.
Limited funding is available from federal and provincial governments at present in Canada. At one time federal agriculture research stations and many universities kept stocks of livestock breeds, but today these stocks are minimal. Provincial governments may assist via museums and farm parks. During the mid 1990’s Agriculture and Agri-food Canada provided resources to develop an inventory of animal genetic resources and to develop criteria and set priorities for conservation. Domestic breeds are recognized as a genetic resource by the United Nations Convention on Biological Diversity (1992) to which Canada is a signatory.
The United Nations Food and Agriculture Organization (FAO) plays a major role in assisting individual countries with conservation programs and provides a forum for international consultation and planning. Their publications and website provide information on methods and resources. At present countries around the world are developing reports on the current status of their genetic resources, for integration into a World Report by 2006. A draft of Canada’s report was submitted to the federal government in September 2002.
The United States has established a National Animal Germplasm program. Activities include a central storage system for genetic material and a database to track resources.
Conferences such as the World Congress on Genetics Applied to Livestock Production provide a forum for scientists involved with genetic diversity. Whenever possible, funding is made available to allow scientists from developing countries to attend.
Further Reading and Resources
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