Abstract
The effective population size of Japanese Black cattle has been significantly reduced and maintaining the genetic diversity of the population is important for breeding of Japanese Black cattle. For the conservation of genetic diversity, use of different lines of the breed with unique genetic characteristics for breeding, instead of intensive use of sires of few particular lines as common in current breeding of Japanese Black cattle, will be effective to prevent the genetic homogenization of the population. In the present study, we performed genetic characterization a population of a rare line of Japanese Black cattle, which has been originated from ancestral “Tsuru-ushi” in Okayama prefecture. By using microsatellite markers, allelic richness, and average observed and expected heterozygosity are 3.48, 0.514, and 0.511, respectively, and these values were lower than those of most of the Japanese Black cattle local subpopulations compared. The result of the clustering analyses indicated that the animals of the rare line formed a single group with a cluster that was clearly distinguished from the other populations. Sequence analysis of mitochondrial D-loop region revealed that only two haplotypes were observed in the population and 80% of the animals in the population possess a single haplotype. However, the other haplotype was a novel unique haplotype that has not been reported in cattle. Genotyping of six genes associated with important traits revealed that SREBP1 and NCAPG loci were fixed for a single allele in the population and more than 90% of animals possess an allele of MC1R locus. These findings indicated that while genetic diversity of the population of the rare line is lower than those of the Japanese Black cattle local subpopulations, this population has unique genetic characteristics that were distinguished from the other populations and, therefore, the rare line is important for maintaining genetic diversity of Japanese Black cattle.
