British Appaloosa Society makes PSSM1 testing mandatory for studbook foals

The British Appaloosa Society (BApS) has made testing for polysaccharide storage myopathy type 1 (PSSM1) a mandatory requirement for its main studbook, following a unanimous vote at the society's AGM in May 2026. Foals entered onto the main studbook must now either test negative for the condition or be verified negative by parentage, based on clear results from both parents.

PSSM1 is an inherited genetic muscle disorder that causes horses to store abnormal levels of glycogen in their muscles, producing signs ranging from mild stiffness to severe tying-up episodes and unexplained lameness. It is most commonly associated with Appaloosas but has been identified in more than 20 breeds. BApS has required PSSM1-negative testing for licensed stallions since 2010, and extending the rule to all main-studbook foals marks the next step in a long-running effort to breed the mutation out of the population.

The British Equine Veterinary Association has welcomed the move, noting that genetic testing supports informed breeding decisions and helps reduce the risk of passing hereditary conditions to future generations. The society is offering reduced registration fees during its 50th-anniversary year to help offset testing costs for breeders. Other bodies, including the Appaloosa Horse Club UK, have run similar testing regimes for over a decade, and welfare advocates hope wider adoption across breed societies could help tackle PSSM1 and other inherited conditions more broadly.