CONSERVATION OF ANIMAL GENETIC RESOURCES
Natural selection tends to minimize genetic variation
within a population so that the individuals within a
wild population are very similar.
Domestication has allowed (required) a vast
accumulation of genetic variation in domestic animal
populations:
- We have put animals in crowded conditions which
selects indirectly for disease resistance.
- We have put animals in environmental extremes which
results in selection for different characteristics in
different populations.
- We have developed numerous local and unique uses,
for example: milk sheep, fat-tailed sheep, draft
animals, chickens to produce feathers for fly-tying.
With the advent of industrial production of meat, milk
and eggs, efficient artificial selection has reduced the
accumulated variation because selection goals and
commercial environments are very similar throughout
the developed world. Selection is based on this
commercial environment and the resulting animals are
used everywhere.
Selection is presently very efficient at changing
populations because:
- Modern reproductive techniques (semen and embryo
freezing for example) allow a selected individual to
produce a vast number of progeny.
- Modern transport allows rapid and efficient diffusion
of genetic material anywhere in the world.
- World industrialisation and a world economy have
combined to make production levels essentially the
only criteria of selection.
This has resulted in an increase in inbreeding in some
populations or a concentration of the power of
selection in the hands of a few companies. For
example:
- Starbuck was a very popular bull at the Centre
d'Insémination Artificielle de Québec (CIAQ). He was
important not only for the daughters he produced
(38,500 daughters were tested in Canada by the fall of
1994) but also for his sons. Eleven of 32 black and
white Holstein bulls in the 1994 CIAQ catalogue are
sons of Starbuck and another is a grandson.
- In the poultry industry each of the major industrial
productions is supplied by fewer than a dozen breeding
companies, none of which are now Canadian. There
are numerous overlaps between these companies and
the industry is still undergoing a consolidation.
The animal industries now commonly use only a few
breeds of any one species. Other breeds have suffered,
some have completely disappeared and others are
represented by only a few individuals.
ONCE WE'VE CHOSEN THE BEST, WHY NOT JUST USE IT?
- To Keep Useful or Potentially Useful Genes or Combination of Genes
- To Take Advantage of Heterosis
- To Overcome Selection Plateaus
- To Provide An Insurance Policy Against:
- For Cultural Reasons
- For Research
The best is presently defined according to industrial
production of a small number of products in a
developed world. The action of genes, including their
potential benefit, is only now being defined. Discarded
animals may carry useful genes.
Examples of single genes which could have been
discarded or lost but which are now used commercially
or are being investigated for commercial use:
- Polled (the absence of horns) was a negative
characteristic in range cattle because the animals
needed their horns for protection. In feedlots, polled is
a positive characteristic because horned animals can
injure each other or their handlers.
- Double muscling in cattle could be considered positive
or negative depending on the situation, but it is used
commercially and is characteristic of the Blanc-Bleu
Belge and Piedmontese breeds.
- Naked neck reduces feathering in chickens and is used
in lines bred for hot climates to reduce the effects of
heat stress.
- Booroola (or other genes for fertility in sheep such as
the Thoka gene from Iceland, or hyperprolific breeds
such as the Java thin-tailed sheep and the Hu sheep of
China) is being investigated in several laboratories
throughout the world.
- Halothane sensitivity in pigs is negative in many
situations but is associated with advantages for meat
production in others.
Once the best is chosen and the others eliminated,
crossing genetically diverse lines to take advantage of
heterosis is no longer possible.
Selection plateaus are reached when the genetic
variation in a population is eliminated. If genetic
variation exists elsewhere, it can be used to overcome a
selection plateau. If it does not exist elsewhere, the
only way of producing variation is by mutation which
is too slow and unpredictable to be useful.
- Future environmental changes, such as changes
brought about by the greenhouse effect or the
development of new feedstuffs, management
techniques or diseases.
- Social changes, such as the recent move to ban cages for
laying hens in Europe, the desire for low-fat foods or the
impopularity of certain production practices, epitomized by
the recent Beef stinks campaign.
- Selection errors. Selecting the best assumes that we
know with precision what the best is. A recent example
of an individual spreading a deleterious gene is that of
the Holstein bull Osborndale Ivanhoe. He carried a
lethal recessive gene for bovine leucocyte adhesion
deficiency (BLAD). His offspring Bell and Sheik were
very popular and spread this gene throughout the North
American dairy herd.
Preservation of our heritage. The vache Canadienne
and the poule Chanteclair are associated with the
development of the French Canadian culture. The
Newfoundland pony and sheep were likewise produced
by the somewhat isolated culture of Newfoundland in
response to harsh environmental conditions. Other
examples of breeds which were important culturally
are the Barred Plymouth Rock and Rhode Island Red
chickens and the Clydsdale, Percheron and Belgian
horses (to name a few) which are associated with
pioneer days. Some of these breeds are being kept to
remind us of our heritage in living history parks.
Zoos often have domestic animals as part of their
displays. For the most past, modern breeds are
inappropriate for this role.
- Control (unselected) lines are needed to measure the
genetic progress in selection experiments.
- Evolutionary studies investigate the genetic reaction of
populations to specific microenvironments.
- Rare breeds or lines are useful for teaching because
they provide alternatives from the industrial norm.
To keep the genetic variation in a form
that is easily recovered
The form varies from live animals to frozen DNA and
the form that is the most appropriate depends on the
eventual use.
To keep local or specialized lines or races
These lines represent combinations of genes developed
for specific purposes or climates.
To keep specific genes
This is the simplest aim to accomplish, especially if the
effects of the genes are visible or the DNA sequence of
the gene is defined.
- Inventory
- Evaluation
- Choice
- Preservation
Existing populations in danger must be identified. One
recent classification ranked populations with fewer
than 100 females as critical, fewer than 1000 as
endangered, fewer than 5000 as vulnerable, and fewer
than 10,000 as rare. These numbers depend on other
factors such as the reproductive efficiency of the
species, whether the population size is increasing or
decreasing and whether frozen material is also being
kept.
A description of the population is needed to allow its eventual
use. Aside from the appearance of the animals, a measure of
the level of performance and the existence of potentially useful
characteristics is needed.
Their are never enough economic resources to save
everything. The choice of populations should be based
on the value or potential value of the line, the genetic
distance to other lines and the vulnerability of the line
to extinction.
Live animals. This is expensive. Populations can be
saved as pure lines (breeds), or as synthetic lines.
Keeping a specific breed is the most appropriate way
of keeping the animals in production (the utilisationist
approach to conservation) because the characteristics
of a breed are usually well defined and it is easier to
attract public interest to a specific breed. Synthetic
lines are started by crossing of two or more defined
lines and they give the advantage of saving material
from all of the original lines by housing and feeding
only one line. The disadvantage is that it is harder to
retrieve the original characteristics of any one of the
original lines. A gene pool is a synthetic line in which
several single genes are kept. It is an efficient means of
saving these genes but ignores the genotypes
surrounding them.
Cryopreservation. Freezing gametes, embryos, cells or
DNA. The semen of some species is routinely frozen.
Unfortunately, eggs cannot presently be frozen.
Embryos of some species can be frozen and while it is
more difficult than freezing semen, it gives the
advantage of saving all of the material instead of only
half. Freezing isolated cells and freezing DNA present
no technical difficulties, but recovering the material in
a living animal is difficult or impossible with current
technology. Because the material cannot be used as
living animals, this provides for a strictly
preservationist approach to conservation.
- Individuals
- The Animal Industry
- Governments
- United Nations
The fanciers who keep animals for expositions. This
group is probably less useful than one might think
because fanciers are generally interested only in a
phenotype. Because of this, the genetic base of an
individual breed may be very narrow.
Conservation groups such as Rare Breeds Survival
Trust (UK), Rare Breeds Canada (Canada) and
American Minor Breeds Conservancy (US) under the
umbrella of Rare Breeds International are formed
specifically to save endangered populations of farm
animals. They are therefore concerned with such
genetic questions as the danger of inbreeding in small
populations. These groups seem to be doing the best
job at keeping farm animal genetic diversity. They
maintain information on the status of endangered
breeds in their respective countries and their members
keep rare breeds on their farms. Funding and
consistency are the major problems.
Farmers of the third world presently own a large store
of genetic variation, but they are replacing their
environmentally adapted animals with improved
animals from the developed world. The primary
consideration for these farmers is their own survival
and they cannot be asked to keep a less productive
animal for the future needs of the developed world.
Middle level producers still keep a quantity of
variation in cattle and pigs, but their primary concern is
again production and they will quickly discard their
lines as soon as a more productive line is offered.
Industrial breeders keep a number of lines to supply
their own needs for genetic variation, but their
previsions are for only ten years and few breeds which
are presently rare are likely to become profitable in that
length of time.
Federal and provincial governments (often through the
university system) at one time kept lines and even
collections of specific breeds of farm animals. In
recent years this has become increasingly difficult and
federal cutbacks have almost eliminated this role.
Local governments may keep some lines in zoos or
historical parks.
Agriculture and Agri-Food Canada has obtained some
resources to establish an inventory of animal genetic
resources and identify those breeds considered to be
endangered. Under the Green Plan established after
the Rio Summit, they have also established two
committees. The Canadian Animal Germplasm
Technical Experts Board, consisting of scientists
representing universities, industry and governments,
gives guidance to the Canadian Steering Committee on
Animal Germplasm, whose members are policy
markers in government and industry. The role of these
committees is to set priorities, identify criteria for
preservation, seek sources of funding, evaluate
applications for funding and act as an information
source.
The UN through the Food and Agriculture
Organisation is active in the organisation of a
conservation system. Unlike the plant situation, there is
no global network of gene banks for animal gene
resource conservation and no coordinated international
structure for active preservation of animal genetic
resources.
More than one site is needed to prevent accidental loss.
The Lippizaner stallions in Croatia give a good recent
example of a crisis threatening a population kept in
only one location. These were moved before they were
destroyed by the civil war in Yugoslavia. When more
than one location is used, some organisation is
necessary to coordinate breeding activities.
Blake, V. (editor), 1992. Breeds and Breeders: A Guide to Minority Livestock
Breeds in Canada. Rare Breeds Canada Inc., Campbellford, Ontario.
Blake, V. and D. Price-Jones (editors), 1994. Raising Rare Breeds: Heritage
Poultry Breeds Conservation Guide. Rare Breeds Canada Inc., Campbellford,
Ontario.
Chiperzak, J., 1994. Raising Rare Breeds: Livestock and Poultry
Conservation: A Producer's Guide. Rare Breeds Canada Inc., Campbellford,
Ontario.
Crawford, R.D., 1984. Assessment and conservation of animal genetic
resources in Canada. Can. J. Anim. Sci. 64:235-251.
Crawford, R.D., E.E. Lister and J.T. Buckley (editors), 1995. Proceedings
of the Third Global Conference on Conservation of Domestic Animal Genetic
Resources. Rare Breeds International, Warwickshire, England.
FAO, 1990. Animal Genetic Resources: A Global Programme for Sustainable
Development. FAO Animal Production and Health Paper 80. FAO, Rome,
Italy.
Hodges, J., 1993. International programmes for animal genetic conservation.
Proceedings VII World Conference on Animal Production 1:235-258.
Lister, E.E. and S.K. Ho (editors), 1995. Canadian Farm Animal Genetic
Resources Conservation: A Plan for the Future. Centre for Food and Animal
Research, Research Branch, Agriculture and Agri-Food Canada, Ottawa,
Ontario.
National Research Council (US), 1993. Managing Global Genetic Resources -
Livestock. National Academy Press, Washington, DC.
Shrestha, J.N.B. (editor), 1992. Proceedings of the First National Workshop
on Conservation of Animal Germplasm. Publication 9206, CFAR, Research
Branch, Agriculture Canada, Ottawa.
Shrestha, J.N.B., 1994. Canada's Animal Genetic Resources: Goat Breeds in
Canada Technical Bulletin 1995-4E, Research Branch, Agriculture and Agri-Food Canada,
Ottawa.
Shrestha, J.N.B., 1994. Canada's Animal Genetic Resources: Sheep Breeds in
Canada. Technical Bulletin 1995-3E, Research Branch, Agriculture and Agri-Food Canada,
Ottawa.
Rare Breeds Canada Inc.
General Delivery
Campbellford, Ontario
K0L 1L0
R.D. Crawford, Chair
Rare Breeds International
Department of Animal and
Poultry Science
University of Saskatchewan
Saskatoon, Saskatchewan
S7N 0W0
D.L. Patterson
Department of Animal Science
Nova Scotia Agricultural College
Truro, Nova Scotia
B2N 5E3
Phone: (902) 893-6653
Fax: (902) 895-6734
E-Mail: DP_AS@AC.NSAC.NS.CA
American Minor Breeds Conservancy
Box 477
Pittsboro, North Carolina
USA 27312
Rare Breeds Survival Trust
National Agriculture Centre
Kenilworth, Warwicksire
UK CV8 2LG
Canadian Foundation for the
Conservation of Farm Animal
Genetic Resources
1710 Woodroffe Avenue South
Nepean, Ontario, Canada
K2G 3R8
Phone: (613) 957-3930
Fax: (613) 957-3931
E-Mail: CFCFAGR@MAGI.COM
F.G. Silversides
Département des sciences animales
F.S.A.A., Cité Universitaire
Québec, Canada
G1K 7P4
Téléphone : (418) 656-7504
Télécopieur : (418) 656-3766
Courrier électronique : 4107FSIL@VM1.ULAVAL.CA
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Canadian Farm Animal Genetic Resources Conservation