Genetic science is an increasingly important consideration in breeding decisions. Information on heritability of traits, genetic disorders, and considerations of breeding in a small gene pool all can be incorporated in selecting matings.
Genetic Diversity Study
The Institute supports research and education so that breeders can maximize their use of scientific advances in this important field. Comments from breeders, such as “The gene pool is so small,” or “How do we reduce the occurrence of genetic disorders without losing diversity?” or “There’s too much reliance on too few stallions” reflect a contemporary concern that the past 50 years of conservation breeding in the West may not guarantee the future of the Desert Arabian horse. Recent scientific advances that identify the genetic cause of some disorders also have breeders wondering how best to breed for the future.
Are things really getting worse? How do we know? What would improve the situation, if improvement were needed? What information can breeders who are deeply committed to perpetuating these desert treasures rely upon?
The Institute has undertaken a genetic diversity study that will:
- Characterize the existing diversity in Desert Arabian bloodlines,
- Track the loss of diversity over time, and
- Make the tools of population genetics available to Arabian horse breeders who wish to consider the long-term health of the breed as a factor in their breeding decisions.
What is the practical application of such a study? For breeders to be able to integrate three goals, based on hard science:
- Perpetuate desirable characteristics that research shows are highly heritable;
- Decrease the frequency of genes that cause disorders such as SCID, CA, and LFS; and
- Retain maximum diversity for the long-term health of the breed.
The study will apply standard population genetics concepts adapted from the International Union for the Conservation of Nature and Natural Resources (IUCN). These concepts have been used in conservation planning for many wildlife species and the maintenance of diversity in rare livestock breeds. Among the measures of diversity to be determined are:
Unique Foundation Dam Lines – How many different mare lines are represented in today’s population? Using mitochondrial DNA, Dr. Ann Bowling determined that some lines derive from a common ancestress (example: Rodania, Roga El Beda, and Venus share a common female line). The number of unique dam lines in the modern population is a key measure of diversity. [more…]
Effective Population Size – How many breeding animals would be needed to represent the diversity of the current herd (usually much smaller than the current population), and has this decreased over time?
Founder Contribution – How much is each original (foundation) ancestor represented in the current population? Knowing the dominant and rare “founders” helps determine the most useful conservation breedings.
Effective Founder Size – How many unrelated animals would be needed to re-create the current population (tracking this over time is one indication of whether diversity is being lost).
Diversity within and between sub-groups – How genetically different are the heritage sub-groups that have evolved in the past 50 years? The sequencing of the horse genome allows researchers to estimate the diversity within and between heritage group and to identify the sub-groups that have rare genes to contribute.
From these and other population genetics measures, we can estimate the trends in diversity and offer recommendations to breeders about how best to conduct future efforts to conserve the Desert Arabian horse.
Genetic disorders in the Arabian breed was the subject of the 2010 Symposium presented by the Institute.
A short explanation of the common genetic disorders found in Arabian horses, how they are inherited, and updated information on testing is here.
The paper prepared by noted attorney Paul Husband and presented at the Symposium is here.
If you care about the long-term genetic health of the Desert Arabian horse, donate here to support the Institute’s research.