Healthy, high-performing horses are the goal of all breeders. The International Association of Future Horse Breeding, or IAFH for short, supports them in achieving this goal. The equine breeding organisations cooperating under the umbrella of the IAFH – currently the Holsteiner Verband, the Oldenburg breed societies, the Trakehner Verband and the Westphalian Studbook – have made it their mission to provide their members with comprehensive access to information from genetic analyses for modern, successful breeding planning. They consider transparency and support in the classification and utilisation of available information to be core tasks.
The IAFH's range of services also includes tests for inheritable diseases such as PSSM2. The abbreviation PSSM stands for polysaccharide storage myopathy, a muscle disorder associated with the excessive storage of sugar in the muscles. This description also applies to PSSM1, but not to PSSM2. PSSM2 encompasses various muscle disorders whose cause is specifically not the mutation responsible for excessive sugar storage. A different genetic basis underlies the disturbances in muscle metabolism or defects in muscle structure that impair muscle function. The often non-specific symptoms include unclear lameness as well as muscle dimples, hardened and tense muscle areas, muscle wasting and ataxia, as well as so-called "training intolerance", which means that the affected horses show little willingness to perform and often appear exhausted after a comparatively short training period. The disease is usually diagnosed in horses aged between seven and ten years, but symptoms can also appear in younger horses, although they are often (still) less pronounced.
Variants of various genes are causally linked to PSSM2. However, carriers do not always develop symptoms; indeed, some horses among them compete very successfully in sport. Feeding and management are considered to be of great importance here, although many questions remain unanswered. The presence of PSSM2 gene variants does not necessarily mean that the tested animal is unsuited for breeding. However, it may be advisable to mate the carrier with a horse that has tested correspondingly negative.
"We IAFH shareholders are now in a position to offer PSSM2 testing for our members' horses using the new laboratory analysis methods. And we can do so under conditions that make it easier to provide more information and transparency on this hotly debated topic," says Dr André Hahn, Deputy Director of Breeding for the Oldenburg breed societies, who is very familiar with the IAFH's main areas of work. "And breeders will soon be able to commission such tests themselves. Our IAFH co-shareholder, the vit computing centre in Verden, will then carry out the corresponding genomic data analyses."
Until then, the breed societies are offering a service to accept requests from their members and forward them to vit for analysis. The procedure is simple: for horses that have already been SNP-genotyped – since the beginning of the 2021 season, all newly registered horses within the IAFH have been routinely tested with SNP markers for parentage verification – no additional sample material or further laboratory analysis is required. For the testing of all other horses, it is sufficient to send in hair samples, after which vit carries out the SNP genotyping in the laboratory and subsequently reads the PSSM2 markers. The horse's UELN (life number) and the client's membership number with the respective breed society must be provided. The net price for SNP genotyping, which is a prerequisite for marker reading, is 20 euros, while the actual PSSM2 test costs 160 euros net.
