breed conservation - sustain D. PHILLIP SPONENBERG, DVM, PHD VIRGINIA-MARYLAND REGIONAL COLLEGE OF VETERINARY MEDICINE VIRGINIA TECH, BLACKSBURG, VA AND - THE AMERICAN LIVESTOCK BREEDS CONSERVANCY

long term long term success depends on a secure commercial use for each breed assures that breeders maintain the breed for their own economic benefit

breeds are made of predictable animals breeds are repeatable “gene packages” can choose specific breeds for specific production goals in specific environments purposes of breeds

high levels of genetic variation make populations that are unpredictable low levels of genetic variation are not viable need to compromise between the two in order to have useful genetic resources

breed management managing breeds assures a useful and successful role for them without planning ahead usually have inbreeding and the problems that come with it

inbreeding arises more rapidly in rare breeds eventually affects all breeds without careful management well-planned management avoids problems breed management

management has various purposes 1.maintain variation and genetic health 2.selection for enhanced production 3.sssure economic return for owners

breeds must have good population structure to have a secure future genetic relationships between the animals are important bloodlines, families, and population structure are all important breeds with high numbers can have inbreeding problems if breeders ignore genetic structure more than numbers

population structure all breeds need to have planned selection and reproduction to avoid inbreeding without this planning selection causes a long, narrow bottleneck

a pyramid elite multipliers commercial standardized breed

“a bag of marbles” no real heirarchy landrace

both types of breeds need planned strategies for selection and breeder animal replacement without planning it is easy to lose the genetic variation that is needed for viability maintain variation

maintaining variation to maintain maximum variation each animal should eventually replace itself each sire produces a son used for breeding each dam produces a daughter used for breeding little or no selection for improved production no population growth

maintaining variation this strategy does not work for selection for improved production without selection the variation stays high predictability can be too low for the breed to be useful in practical production settings

maintenance at the other extreme is the model used for modern industrial poultry or dairy cattle artificial insemination with a single male and thousands of females predictability of production is high general health and resistance are low because genetic variation is low

maintenance need to compromise between selection and management of inbreeding can assure the use of many sires, and that all of them contribute to the next generation goal is an adapted population that is viable and productive

using several sires that have different grandparents minimizes bottleneck using several sires that all have the same sire or grandsire assures a bottleneck maintenance

important to assure that all herds contribute to the next generation if all sires come from a single herd, this is similar to having all sires come from the same family maintenance

each sire produces a sire one sire produces next sires dramatically decreases genetics

maintenance difficult to assure that all herds are providing sires breeders usually have culture where a few breeders are powerful, most others have little influence powerful breeders provide sires for most others rare breeds need to have a much wider genetic base than occurs with this strategy

the same strategies can work well within a single herd ALBC has developed a “conservation breeding program” for long-term management of breeds within a herd

conservation breeding program the herd is divided into three groups (bloodlines) within a single herd (a, b, c) on the basis of genetic relationships one sire at a time is used over the entire herd the herd maintains crosses between the three groups (crossbred or linecrossed), as well as animals that have a majority genetic influence from each of the three groups (linebred)

conservation breeding dams:ABC Year 1 sire A A/A=AA/BA/C year 2 sire BA/BB/B=BB/C B/AB=BB/AC year 3 sire CA/CB/CC/C=C C/ABC/ABC/BC=C C/BAC

conservation breeding ABC year 4 sire AA/A=AA/BA/C A/AC=AA/BCA/BC A/AB=AA/AB=AA/ABC=A likewise into the future key is to move of genetic material from linecrosses back into the lines from generation to generation the genetic material is moderately inbred in alternate generations, and outbred in the others

conservation breeding every step has opportunities for selection for performance in cattle this works well, because a single two year old bull can be used in any one year multiple bloodlines assures that there will be crosses among them, as well as moderately linebred animals within each bloodline. these are replenished in each year depending on the sire used

conservation breeding using linebred sires from each bloodline assures that these will be distantly related to the females of the other bloodlines assures that linecrosses are always possible using linecross sires assures that few matings are linecrosses, so inbreeding increases complicated in the beginning stages after it is started it is easy to continue select a linebred replacement sire each year use when two years old

conservation breeding in one sample year these are the males: a two year old bull (or two), used over the herd, from bloodline “A” a yearling bull (or two or three), from bloodline “B” to use next year bull calves from bloodline “C” to use in two years

conservation breeding sires are selected from those linebred to the bloodine of the year dams are selected from two sorts of females linebred to the bloodline of the year linecross between the bloodline of the year and the other two bloodlines

conservation breeding assures that the genetic material is in a linecross condition in some animals/generations, and a linebred condition in other animals/generations permits selection in both conditions shapes a strong genetic structure

conservation breeding can be tailored for different situations herds can be split to use multiple males each year include both linebred and linecross matings in each group multiple herds can cooperate by periodic exchange of males

managing landraces in landraces it is nearly impossible to discover all animals of the breed nearly always pure animals or herds that have escaped documentation the breed will be changed from including animals that are not pure also important to include all pure ones in order to keep the breed strong genetically

landraces most landraces have an inspection process in order to include new animals into the registry

landraces always better to inspect an entire herd for purity than it is to inspect individual animals mistakes less likely with a herd than with individual animals

genetic management every breed has a few animals in it that have great importance for the genetic health of the breed usually animals with rare bloodlines or from rare families important to discover and document these to not lose their genetic influence

important individuals unique or important sires can be used relatively widely in the breed unique or important dams can be mated to their own sons, trying to get a son that is 3/4 the genetic influence of the original dam, and then use the son widely