Farm Animal Genetic Resource conservation

What, why and how

Reasons for genetic conservation

1. We need to keep potentially useful genes and gene combinations

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.

3 Examples

Example1

• Non-intensive agricultural production systems may not want genes for prolificacy, such as the Booroola gene in sheep which increases the number of lambs per mating. Hyper-prolific lines of sheep and swine are of value in modern production systems.

Example2

• Porcine stress syndrome in swine can lead to undesirable quality in the pork, but the condition has been associated with faster growth. DNA tests now allow us to select directly against the allele linked with this condition.

Example3

• DNA tests have now been developed and commercialized to allow selecting beef cattle directly for meat tenderness, using the calpastatin gene. Frequency of this gene varies among breeds.

2 To take advantage of heterosis (hybrid vigour)

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.

3 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.

4 To provide an insurance policy against

• climate change • spread of disease, especially in monocultures • changing availability of feedstuffs • social change, such as issues of animal welfare and

environmental sustainability • selection errors: a widely used sire may spread a

genetic disease throughout a population before the problem is identified

5 For cultural reasons

Human history is closely linked to agricultural practices and use of particular breeds. 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.

6 For Research

• 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.

For Research

• 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 for 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.

Goals for conservation

To keep specific genesAs 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

InventoryDefinition 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.

Steps necessary for conservation

EvaluationStocks 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

• 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.

Preservation• 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• Individuals

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.

Individuals

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.

Conservation Groups

• Breed organizations, and private producers obtain funding and provide resources and information on conservation of animal genetic resources. Membership includes farmers, scientists, breed associations and commodity organizations.

Government

Limited funding is available from national governments for conservation. Agriculture research stations and many universities keep stocks of livestock breeds, but today these stocks are minimal.

FAO• 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.

Conferences

• 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.