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