Japanese researchers have found notable genetic differences between horse breeds which appear to play an important role in their personalities.
Genetic variations related to neurotransmitters or hormones are known to affect personality or behavioral traits in many animal species, including humans.
The researchers, led by Yusuke Hori, investigated breed differences in horses in the dopamine receptor D4 gene (DRD4), which has been reported to affect horse personality.
They collected samples from seven breeds in all – two breeds of European origin, the thoroughbred and Selle Français; one South American breed, the Criollo; three native Japanese breeds, Hokkaido, Taishu and Yonaguni; and one native Korean breed.
Hori and his colleagues then compared the sequence of the DRD4 gene in one particular chromosomal region among these breeds.
They drilled down and found important differences, especially in the frequency of one allele associated with low curiosity and high vigilance, which was much lower in native Japanese horses than in thoroughbreds. Some of the differences appeared to be breed specific, they said.
“This difference may account for breed differences in personality or behavioral traits,” the researchers said.
The researchers, whose findings were publishing in the Journal of Equine Science, published by the Japanese Society of Equine Science, noted that selective breeding had resulted in great diversity between different breeds in domestic animals, not only in body size and coat color, but also in behavioral traits and personality.
Differences between breeds in personality, as measured by questionnaire surveys, were also reported in horses, they said.
In total, 70 samples were collected for analysis across the seven breeds.
They identified several novel variations that seemed to be breed-specific. They said the differences may be a result of different breeding histories or of geographical variation.
“They may affect the variance of behavioral traits or personality among the breeds. Further studies of both functional aspects of genes and behavioral variations are needed to validate the effect of these polymorphisms,” they said.
Breed Differences in Dopamine Receptor D4 Gene (DRD4) in Horses
Yusuke Hori, Takatoshi Ozaki, Yoshimitsu Yamada, Teruaki Tozaki, Heui-Soo Kim, Ayaka Takimoto, Maiko Endo, Noboru Manabe, Miho Inque-Murayama, and Kazuo Fujita
J. Equine Sci. Vol. 24, No. 3 pp. 31 – 36, 2013
The full study can be read here.