Control of Recessive Genetic Disorders in Japanese Black Cattle Using DNA-Based Genetic Diagnostic Tests

The effective control of genetic disorders is essential for animal welfare and sustainable production. Since 1996, 10 causative mutations in autosomal recessive genetic disorders have been identified in Japanese Black cattle, leading to the development of DNA-based genetic diagnostic tests. The government has published profile sheets detailing genetic disorders and designated seven of these disorders as having a significant economic impact, prompting a response policy using DNA-based genetic diagnostic tests to reduce their occurrence. However, the effects of these tests on the frequency of risk alleles have not yet been evaluated. In this study, we analyzed the risk allele frequency trends over two decades using a large-scale dataset from central slaughterhouses. We found that following the publication of the profile sheet, the frequencies of the risk alleles rapidly declined, reaching very low levels. For such a rapid decline to occur within three generations, a significant proportion of asymptomatic heterozygous carriers would need to have been eliminated from the breeding system. This level of removal is considered unattainable through natural selection alone, indicating the need for DNA-based genetic diagnostic tests. These results showed that DNA-based genetic diagnostic tests were effective in suppressing the frequency of risk alleles in the population.