Transcript Document
conserving endangered genetic resources D. PHILLIP SPONENBERG, DVM, PHD VIRGINIA-MARYLAND REGIONAL COLLEGE OF VETERINARY MEDICINE VIRGINIA TECH, BLACKSBURG, VA AND- THE AMERICAN LIVESTOCK BREEDS 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 industrial very productive very 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? breeds more than a package of genes a predictable and repeatable genome need genetic uniformity to serve usefully available immediately for specific situations reasons to conserve agricultural security conserve variations for a future that is secure and comfortable, including ecology scientific. genetic variations of interest animals (diseases, products) humans (models of disease) cultural national 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 term long 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 importance heritability of adaptation is low heritability 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 cultural heritage many breeds reveal much about the unique history of different groups of humans 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 current production production requires selection selection always selects some and rejects others rejecting and animal is not only rejecting a few genes, but the entire genome of the animal it is important to maintain enough variation to assure rugged adaptation and general health, and to avoid inbreeding depression 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 future a secure future requires a wide range of breed types breeds are predictable can quickly serve their role when needed valuation the value of a breed is important the value of individual animals within a breeds is also important 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? value of animals 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 short term short term - best to rank breeds by balanced method animal products do have economic value replacement costs also have value both 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 long 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 value 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 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 choosing breeds 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 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 organization in USA 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 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 them has helped some breeds with registry function helps with genetic management helps with marketing or products rescues 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 landraces many of these have no registry not all breeders will register animals however it is done, some idea of population size is required to conserve the breed