Genetic characterization of phenotypic traits in endangered Taishu horse breed and their breeding strategy.
Authors: Yoshihara Tomoko, Tozaki Teruaki, Nakaya Sakura, Takasu Masaki, Kawate Koki, Furukawa Risako, Kikuchi Mio, Isihge Taichiro, Nagata Shun-Ichi, Kakoi Hironaga, Hobo Seiji
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Genetic Characterisation of Taishu Horse Phenotypic Traits Preserving the genetic diversity of endangered horse breeds requires understanding which allelic variants control their distinctive traits, yet few studies have systematically genotyped coat colour, conformation and gait genes in critically small populations. Researchers genotyped 56 Taishu horses—a severely threatened native Japanese breed—for nine genes harbouring variants associated with coat colour, body size and movement, identifying polymorphisms in only three of these loci. Coat colour inheritance aligned precisely with predicted genotypes, with the notable exception of black-coated individuals that exhibited seasonal phenotypic variation (dark in winter, lighter brown in summer), whilst the myostatin gene showed negligible polymorphism and no gaited alleles were detected in the population, confirming the breed's characteristic trot. Body measurements (mean withers height 122.8 cm, chest circumference 143.1 cm) showed no association with the genetic variants examined, suggesting these conformation traits are either controlled by unmeasured loci or influenced substantially by environmental factors. For conservation breeding programmes, these findings highlight the critical importance of deliberately pairing carriers of rare alleles—particularly those producing black and chestnut phenotypes, which are markedly underrepresented compared to bay horses—to prevent further erosion of the breed's phenotypic spectrum and inform similar strategies for other declining native Japanese breeds.
Read the full abstract on PubMed
Practical Takeaways
- •Breeders should prioritize genetic testing for coat color genes to preserve rare black and chestnut phenotypes in Taishu horses, which are underrepresented compared to bay horses
- •Seasonal coat color changes in black Taishu horses are genetically determined and should be expected; this is a breed characteristic, not a health concern
- •Current genetic markers do not predict body composition in this breed, so traditional conformation assessment remains necessary for selective breeding decisions
Key Findings
- •Only 3 of 9 genes investigated showed polymorphisms in 56 Taishu horses, with coat color phenotypes accurately predicted by genotypes
- •Black horses exhibited seasonal coat color variation (black in winter, light brown in summer), a breed-specific phenotype
- •No significant relationship found between genetic variants and body measurements (withers height 122.8 cm, chest circumference 143.1 cm, cannon circumference 16.9 cm, body length 130.2 cm)
- •Gaited allele was absent; all horses exhibited trot phenotype as predicted by doublesex and mab-3 related transcription factor 3 gene genotypes