Conserving endangered genetic resources D. PHILLIP SPONENBERG, DVM, PHD VIRGINIA-MARYLAND REGIONAL...
Transcript of Conserving endangered genetic resources D. PHILLIP SPONENBERG, DVM, PHD VIRGINIA-MARYLAND REGIONAL...
conserving endangered genetic resources
D. PHILLIP SPONENBERG, DVM, PHD
VIRGINIA-MARYLAND REGIONALCOLLEGE OF VETERINARY MEDICINE
VIRGINIA TECH, BLACKSBURG, VA
AND- THE AMERICAN LIVESTOCKBREEDS CONSERVANCY
current situation
agriculture and animal production have changed more in the last century than in 10,000 years
why conserve breeds?
conservation needs to be rational and useful
genetic resources (breeds) have an essential role in agricultural systems
current situation
animal production is becoming more industrialvery productivevery narrow and defined
currently very few genetic resources produce the majority of meat and milk
current situation
industrial production results in more and more breeds becoming rare or extinct
why are breeds important?
breedsmore than a package of genesa predictable and repeatable genomeneed genetic uniformity to serve usefullyavailable immediately for specific
situations
reasons to conserve
agricultural securityconserve variations for a future that is secure and
comfortable, including ecology
scientific. genetic variations of interest
animals (diseases, products)humans (models of disease)
culturalnational or regional heritage
agricultural security
short term: meat, milk, wool, services (transport, draft, management of environment) all in the present day
long term: these will all be needed in the future, in a system that provides them over centuries
security
need strategies for short and long termlong term survival is impossible without short
term survival
security
agricultural systems will change in the next years and centuries
details of those changes are unforeseeable
need to conserve the genetic components (breeds) to ensure that future generations can choose the ones they want to use
security
local and adapted breeds have high importanceheritability of adaptation is lowheritability of production is medium to high
achieve a population of animals that is productive AND adapted more rapidly if the starting point is with an adapted population rather than a more productive one
science
animals provide opportunities to study genetic variation
each breed has its own unique combination of genetic variation
losing breeds means losing this variation
cultural heritage
breeds result from interactions between animals and humans
breeds are a living history of this old and important relationship of animals and civilization
tells us who we are and where we have come from
many breeds reveal much about the unique history of different groups of humans
cultural heritage
cultural heritage
many human groups have their own breeds that are old and central to their cultural identity
if this is the only value of a breed:the breed can persist in low numbers without much risk of genetic erosion or risk of extinction
cultural heritage
population management can be directed at maintaining adequate genetic variation
replacement of breeding animals based on genetic structure of breed rather than improvement
can succeed with small populations (minimum of 100 animals, more is always better!)
current production
current production depends on population expressing good characteristics at a high level
requires a high level of genetic variation to maintain production
demands a high population level (thousands) to allow for selection for production
production requires selectionselection always selects some and rejects othersrejecting and animal is not only rejecting a few
genes, but the entire genome of the animalit is important to maintain enough variation to
assure rugged adaptation and general health, and to avoid inbreeding depression
current production
current production
difficult to maintain selection in very small populations without causing problems from inbreeding. Most decision need to be made with regard to genetic structure of the population, leaving few decisions for selection for production.
future production
agricultural systems change over time
these changes are difficult to predict
every human generation considers itself wiser than the others, but history indicates that each has a great deal to learn from other generations
a secure future requires a wide range of breed types
breeds are predictablecan quickly serve their role when needed
future
the value of a breed is importantthe value of individual animals within a breeds is
also important
valuation
value of animals
how to measure the worth of animals and breeds is important
rate of gain?milk production per year?milk production over lifetime?longevity?individual replacement cost?
each method results in a different result for genetic selection
short term production usually favors developed or industrial animals
cost of replacement usually favors adapted and resistant animals
value of animals
short term - best to rank breeds by balanced method
animal products do have economic valuereplacement costs also have valueboth need to be considered
some productive animals have high replacement costs
less productive animals can have much lower replacement costs
short term
most adapted animals are smaller than more productive animals
not certain whether animals divide their metabolic resources between production and adaptation
a “total” whether they need to divide them between the two goals
in some cases (Beefmaster catte) it is possible to have both high production and adaptation in benign environments
short term
goal is to conserve options for future generations
we have received a complete range of breeds from our ancestors
we need to pass this along to our descendants
long term
in an ideal world each breed would have high enough numbers to permit selection
not always possible
long term
important to include all possible factors to assign worth or value to breeds
document what they offer to production systems
long term usually best to use combination of local adapted breeds with production/industrial ones
value
production systems
breeds can be used in different ways
purebred industrial breeds usually lack adaptation
purebred local adapted breeds usually lack high short term production
production systems
the two types can be crossed for productive use
these crossbreeding programs nearly always endanger the local breed
usually the industrial breed gets all the credit for the resulting production of the crossbreds
really both parents are equally important
production systems
long term crossbreeding systems depend on pure breeds with good adaptation and production
can select a breed for just about any characteristic
production characteristics have medium or high heritability
adaptation and reproduction characteristics have low heritability
choosing breeds
developing a breed that is both productive and adapted is quicker by starting with adapted breed instead of a more productive breed
this idea is usually rejected in favor of a more rapid answer, even though it does not work
choosing breeds
organization
conservation needs to be effective
with improved communication and transportation, conservation must be organized
isolation that served well in the past to conserve breeds is no longer the situation
without organization many breeds will be lost
organization
each country needs its own style of organization
no single model will work in all countries
the governmental USDA preserves embryos and semen, has little interest in live animals
non-governmental work is mostly through the American Livestock Breeds Conservancy
conserving breeds for over 30 years
organization in USA
ALBC
founded in 1978 by historians to conserve local breeds that were in danger of extinction
grown into a conservation organization that works with breeds of livestock as essential for diverse agricultural systems that function well
ALBC
studies breeds and populations to conserve themhas helped some breeds with registry functionhelps with genetic managementhelps with marketing or productsrescues populations at risk of extinction
ALBC
how best to measure populations?
in the North American situation it is logical to use the number of animals registered in each year
this indicates the level of purebred breeding
reveals the activities of the breeders
ALBC
annual registrations work poorly for landracesmany of these have no registrynot all breeders will register animals
however it is done, some idea of population size is required to conserve the breed