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:

1. Perpet­uate desir­able char­ac­ter­is­tics that research shows are highly heritable;
2. Decrease the frequency of genes that cause disor­ders such as SCID, CA, and LFS; and
3. 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.

The full study plan is found here, and infor­ma­tion about the mito­chon­drial DNA part of the study is here.

Genetic Disor­ders

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.