Evaluation of inbreeding and founder-based genetic diversity in Hanwoo cows

This study evaluated inbreeding and the pedigree structure and genetic diversity using pedigree records in Hanwoo cow population. The analysis included 167,422 Hanwoo cows born between 2010 and 2024 that were registered in the national pedigree system. The level of inbreeding increased steadily in recently born animals, and higher inbreeding coefficients were also observed as the pedigree depth increased. In the analysis of pedigree completeness index (PCI) and founder contribution, PCI values tended to increase in recently born animals. Regarding sire usage, the total number of offspring produced, the number of sires used for mating, and the average number of offspring per sire showed a continuous increase over time. The number of effective sires that were frequently used for mating also increased. However, sires ranked within the top 10% for genetic merit accounted for about 60% of the total genetic contribution, indicating that dependence on a small group of high-ranking sires remained at a high level. When major sire contributions were examined, the top five sires together accounted for 4.662% of the total genetic contribution. When the range was extended to the top 20 sires, this value increased to 13.068% in Hanwoo cow population. When the contribution of specific sires remains high within a population, further increases in inbreeding and continuous reduction of genetic diversity can be expected. This may lead not only to changes in growth-related traits, but also to reduced reproductive performance and increased risk of inbreeding depression. Maintaining long-term genetic diversity in Hanwoo cow population may require limiting further accumulation of inbreeding. This could be done by using a wider range of sire and dam lineages in selection, along with efforts to keep the breeding system stable over time.