Genetic Variant of the Canine FGF5 Gene for the Hair Length Trait in the Akita: Utility for Hair Coat Variations and Welfare in Conservation Breeding

<b>Background/Objectives</b>: Variations in hair length are observed in many dog breeds, as determined by the canine <i>FGF5</i> gene. Long-haired Akitas, which are disqualified under breeding standards of Akitas, are sometimes born to short-haired parents and may have been subjected to treatments compromising animal welfare. Here, we aimed to identify an <i>FGF5</i> variant associated with hair coat variations in Akitas in Japan, and to assess how welfare of this breed can be improved by carefully planned breeding. <b>Methods</b>: DNA samples were obtained from 60 Akitas in 2021 (modern Akitas) and 73 Akitas in the 1970s and the 1980s (classic Akitas). Sanger sequencing was performed on all exons and exon-intron junctions of the <i>FGF5</i> gene to determine the causative variant of long hair in Akitas. A real-time PCR assay was developed to genotype <i>FGF5</i>:c.578C>T in modern and classic Akitas. Using 54 dogs from modern Akitas, scores (1 to 10) of hair length were compared among the three genotypes (C/C, C/T, and T/T). <b>Results</b>: Sanger sequencing revealed that the canine <i>FGF5</i>:c.578C>T variant was associated with long hair in Akitas in Japan. Genotyping revealed that the frequency of the mutant T allele was 0.350 in modern Akitas, which was significantly higher (<i>p</i> < 0.001) than in classic Akitas (0.212). The three genotypes were not in Hardy-Weinberg equilibrium (HWE) in modern Akitas but were in HWE in classic Akitas. There were significant differences in hair length scores among the three genotypes (<i>p</i> < 0.001) and between the C/C and C/T genotypes (<i>p</i> < 0.005). There was no significant difference in the scores between male and female dogs. <b>Conclusions</b>: This study revealed that a causative variant that determines the long hair trait of Akitas in Japan was the <i>FGF5</i>:c.578C>T variant, which was inherited in an incompletely dominant manner. Akita dog breeders were more likely to select heterozygous C/T dogs based on the appearance of the hair coat for breeding dogs with an ideal fluffy hair coat. This might result in a high mutant T allele frequency and the production of undesired long-haired Akitas with T/T, which may create welfare problems. Genetic testing for this variant is necessary to improve welfare and conserve the Akita breed.