The gaited horses - Genetics
Next to their basic gaits: walk, trot and gallop, gaited horses can perform some additional gaits. These horses can use alternate gaits at intermediate speed. Based on the variation in footfall pattern, timing and cadence, these gaits may be a pace or a kind of ambling. In 2012, Andersson and his team of researchers found a mutation in the gene DMRT3 which is responsible for the trait of performing those additional gaits. Examinations of Icelandic Horses showed a close relation between the presence of the gene and their ability to execute ambling gaits and pace. Further studies of different horse breeds indicate the heritable characteristics of various breeds performing ambling gaits; while the non-gaited horse breeds lack the DMRT3 gene. The genotyped Icelandic Horses prove that all five-gaited individuals, which perform additional gaits like tölt and pace next to their basic gaits walk, trot and gallop, are homozygote A/A for the mutation of the DMRT3 gene. Horses with heterozygote C/A genotype can sometimes execute ambling gaits as well. In contrast, horses which only perform walk, trot and canter are often homozygote for the wild-type allele C/C. In addition, the studies have shown that the DMRT3 gene is responsible for the clear beat in American trotting and pacing horses. This assumption was confirmed by the successful racing results of homozygote A/A individuals. These racing horses trot in high speed and perform it well, whilst most horses would break into their physiologically faster gait gallop. All the tested trotters maintained the trot at this fast speed, excluding two trotters which have not shown the mutation of the DMRT3 gene and have had problems to keep trotting in faster speed without changing to gallop. Basically, the ambling horses can perform special gaits next to their square gaits (walk, running walk, tölt) which can be shifted either laterally towards pace or diagonally, approximating trot. According to their breed, they have particular names for their special gaits. Furthermore, the gaits can be executed in diverse style and manner. It depends on the individual breed whether these gaits are naturally available or must be trained. For example, in Tennessee Walking Horses, walk is natural and Saddlebred Horses have to be trained in their breed-specific gait rack. Relating to the genes in the Mangalarga Marchdor breed, it is shown that the genotypes are responsible for their tendency of performed gaits. The marcha batida is mostly associated with the genotype C/C, while most of the individuals performing the marcha picada have the genotype A/A.