Evaluation of recent changes in genetic variability in Japanese thoroughbred population based on a short tandem repeat parentage panel.

The research article explores the changes in genetic variability in the Japanese thoroughbred horse population over a 15 year period, using a panel of short tandem repeat (STR) markers. The findings show a decrease in genetic variability and highlight the importance of monitoring these changes to maintain effective parentage control.

Understanding the Scope of the Research

• The study focuses on understanding the fluctuations in genetic variability in the Japanese thoroughbred horse population, focusing on the impact of selective breeding (breeding based on desirable traits such as racing performance).
• The researchers studied allele frequencies and the probability of exclusion (PE – a measure of the effectiveness of statistics used in genetic testing) of 16-17 loci (specific locations of genes on a chromosome) in a parentage panel.
• This study was conducted over 15 years, providing a longitudinal perspective on the changes in genetic variability.

Key Findings of the Research

• An analysis of the Expected Heterozygosities (He – a measure of genetic diversity) of 14 loci indicated a decreasing trend, suggesting a significant decrease in the average He of the thoroughbred population over the study period.
• The researchers propose that this decrease in genetic variability may have been induced by a reduction in the population size and selective breeding bias, where specific traits are chosen over others, reducing overall genetic diversity.
• Four loci showed a significant increase in allele frequency and a significant decrease in He, suggesting that positive selection or selection of advantageous traits for horse racing impacted these loci.
• While there was a decrease in PE due to a decrease in genetic variability, the PE remained high, signifying the continuing effectiveness of the STR parentage panel for genetic testing and control.

Implications and Future Directions

• The findings of the research underscore the ongoing need to monitor genetic variability in the thoroughbred population to maintain robustness and reliability of DNA parentage testing.
• The current STR panel remains effective for maintaining parentage control, however, continual monitoring is essential due to the observed decrease in genetic variability over the 15-year span.
• The results also suggest that breeding practices may need to be examined to avoid significant decreases in genetic diversity in the population.