Special horse breeds and types have been bred or selected to maximally fulfil the demands of the various equestrian disciplines. Previous methods or systems for the selection of sport horses and breeding stock were time and labour consuming. Genetic testing for the predisposition to certain lateral gaits or to sprinting or stayer aptness appears practicable and is less costly. Information on the genotype may become a major support in career planning. With the g.66493737C>T SNP in the myostatin gene the predisposition of thoroughbreds to optimal racing distance can be assessed. Furthermore, a mutation in DMRT3 has influence on lateral gaits. Five-gaited Iceland horses and some other gaited horses as well as American Trotters and Pacers are homozygous for this mutation. In contrast, 23% heterozygous animals were found in the French trotters breed. Regardless of the genotypes, by performing intensive exercise net protein degradation in muscle is induced. This muscle damage needs to be repaired in the recovery phase. By the administration of properly selected amino acid/protein mixtures exercise induced muscle protein degradation is inhibited. The best strategy is to ensure that the required AA are at the right moment and place in the muscle before it starts to degrade. Thus mixture must be provided just before or shortly after each form of exhaustive exercise. In a field trial with thoroughbred race horses, the supplemented horses had the longer and better racing season winning more prize money too.