The NZWA would like to advise its members about a genetic condition which has been discussed in the equine media as of late. The condition is called Warmblood Fragile Foal Syndrome or (WFFS).

It is an autosomal recessive defect. This means that both males and females can carry the gene and that in-order for a horse to be affected with WFFS the animal must inherit the gene from BOTH parents. It seems largely confined to the Warmblood breeds of horses and has been found across most lines and studbooks. Studies have shown that between 9 and 11% of warmblood horses carry one copy of the WFFS, this makes these individuals carriers of WFFS. These animals are not affected in any way. However, when two carriers breed then there is a 25% chance the foal will not be a carrier (N/N), and 50% chance it will receive a single copy (N/FFS) and is then a carrier, and a 25% chance that it will receive two copies of the gene (FFS/FFS) and become a nonviable pregnancy, it will normally result in a loss prior to birth. Occasionally a stillbirth occurs and very rarely a living FFS/FFS foal is born. These foals show defective skin and connective tissue which results in severe abnormalities and lesions. Sometimes the belly cavity is open. This condition is untreatable, and the affected animal will die or be euthanized.

NZWB Recommendations

In order to prevent breeding losses and affected pregnancies the NZWA strongly recommend that breeders test their mares for this condition. 

Any carrier mares (N/FFS) should only be bred in the future to non-carrier stallions ((N/N). Please ask the owner of your chosen stallion to advise you of the stallion’s status regarding WFFS. 

Some registries overseas are mandating testing for stallion owners. In New Zealand we strongly recommend that stallion owners test their breeding stallions. 

If a stallion owner discovers that they have a carrier stallion (N/FFS) it is recommended that they follow best practise and require their client mares to be tested and only accept non-carrier mares. This best practise approach will ensure that in New Zealand we minimise any future breeding losses that are now known to be associated with WFFS. 

There is no need to retire carriers from breeding, just select non-carriers as breeding partners.

Jody Hartstone
President - NZ Warmblood Assn