Genetics and Breeding

All of the Dales Ponies at Cascadia Heritage Farm have tested negative for FIS and PSSM1 (information below), and they are entered in a clinical trial that involves testing for genetic variants of PSSM2 (so far all negative).  We also strive to maximize genetic diversity of our own stock, keeping multiple stallions and working on crossing each mare to each stallion to the extent that this is possible without too close line-breeding.  This practice of crossing each mare to multiple stallions will help us maintain and eventually increase the genetic strength of this amazing breed.  Key to this is having as many male ponies producing offspring as possible.  The stallions used for breeding should of course meet the breed standard, be licensed stallions, and be free from genetic disease.  Thankfully the quality of Dales Ponies is generally very good, so most can meet these standards.  Dales Pony stallions are remarkably kind and generally easier to handle than stallions of other breeds often can be.

Genetic diversity within the Dales Pony breed worldwide AND within the United States is quite good considering the low overall numbers.  However, many people still seek to breed their mares to certain stallions that show well or otherwise appear desirable.  This is understandable and fine, as long as a conscious effort is also made to continue to breed to the less well-known stallions and less well-represented family lines, in order to maintain genetic diversity and avoid concentrating genes that can become deleterious.

The Dales Pony breed is less plagued by heritable disease than many other horse and pony breeds.  However, some undesirable genetic mutations are present in the breed in low numbers, and care must be taken to minimize the transmission and concentration of these mutations.  Our goal here at Cascadia Heritage Farm is to actively preserve a healthy gene pool and by doing so, to maintain a breed that can be a wonderful partner to encourage an agricultural lifestyle and preserve the values of animal husbandry – – –  and ultimately to encourage hope and appreciation.

One key idea to keep in mind regarding maintaining a healthy and genetically diverse population is that each Dales Pony mare of sound temperament and conformation should produce at least one foal.  Her line will die with her if this does not happen.  It is even better if she produces more than one foal, with more than one stallion.

HERITABLE PROBLEMS:

Polysaccharide storage myopathy (PSSM) is NOT common in Dales.

https://cvm.msu.edu/research/faculty-research/comparative-medical-genetics/valberg-laboratory/type-1-polysaccharide-storage-myopathy

https://www.centerforanimalgenetics.com/web/wp-content/uploads/2019/01/PSSM2-Infosheet-Vets-English.pdf

 

Foal Immunodeficiency Syndrome, or FIS, is a devastating disease with a 100% mortality rate of affected foals within the first few months of life.  Affected foals are unable to produce antibodies and will succumb to infection.  It is a recessive genetic disease, meaning the foal will only be affected if BOTH parents are carriers of the mutation that causes the disease, AND have passed the abnormal gene on to the foal.

This mutation has been identified in Dales Ponies, Fell Ponies, and Gypsy horses.  The good news about this mutation is that carriers are completely unaffected, and as long as at least one of the parents is not a carrier, it is impossible for the foal to have the disease.  There is now a policy that all Dales Pony stallions MUST test negative for the FIS gene mutation in order to be licensed to breed.  There are a few older stallions that were licensed before this rule went into effect, and some of these have not been tested for FIS.  If you are breeding a mare to a stallion that has not been tested or is a known carrier, it would be prudent to have the mare tested to make sure she is not a carrier of the FIS mutation.

On the off chance that an FIS-carrier mare would be bred to an FIS-carrier stallion, the resulting foal would have a 25% chance of being FIS clear, a 50% chance of being a carrier like its parents, and a 25% chance of being born with the fatal disease.

Some breeders choose to test all breeding stock, and some only test stallions.  As long as the current policy requiring stallions to be clear of the  FIS mutation remains in effect, both strategies will prevent the birth of affected foals.  Breeding unlicensed or unregistered stock could lead to foals being affected.

There is no advantage to breeding out FIS carriers, as long as breeders are thoughtful about which mares they breed to any remaining carrier stallions.  In fact, eliminating FIS carriers would narrow the gene pool in this critically endangered breed, which could carry other unintended adverse genetic consequences.

Testing for the FIS gene mutation is available through multiple laboratories in the United States and one in the United Kingdom.

https://dpcna.com/fis-in-dales-ponies

 

Melanoma:  All grey horses are prone to melanoma, which can become fatal as they age.  Dales Ponies are no exception.  Those that are homozygous grey have an increased risk for developing melanoma and developing it earlier in life, when compared to those that are heterozygous grey.  Breeding two grey ponies together increases the likelihood that offspring will be homozygous grey.  It is good to know whether a breeding pony is homozygous or heterozygous grey, and genetic coat color testing is readily available to the public.

https://dss.ncf.edu/cancerwiki/index.php/Equine_Melanoma_in_Grey_Horses

 

Equine Metabolic Syndrome (EMS) can affect Dales Ponies, as it can affect many other horse and pony breeds referred to as “easy keepers,” those adapted to life with sparse forage.  Some are more prone than others, and EMS appears to be heritable to a fairly large degree based on results of research done thus far.  Avoiding breeding two affected ponies to each other would make sense, as would focusing more on unaffected ponies of the same bloodlines in a breeding program.

https://www.veterinarypracticenews.com/is-equine-metabolic-syndrome-heritable/#:~:text=The%20heritability%20of%20temperament%20is,shaping%20a%20mature%20horse’s%20disposition.