Genetic improvements in closed breeding herds of pigs in Japan

Abstract

Closed breeding herds of pigs in Japan are used for the development of pig strains (DPS). The program was started in 1969, and has since produced nearly 100 strains. Until the 1990s, the selection index method was used to achieve the relative desired changes, followed by the restricted BLUP method ; and since the 2000s, the BLUP method has been used, which employs weighted values of objective traits for improvement that are estimated from the family selection index. During this latter period, a considerable number of studies have been conducted, including theoretical research on selection methods and inbreeding prevention in DPS, and the estimation of genetic parameters based on actual data obtained from DPS. Traits that were not included at the outset of DPS, such as female reproductive traits, body size, and robustness, have also been added to the list of objective traits. We conclude by discussing the significance of the contribution of DPS to the genetic improvement of pigs in Japan and new genetic improvement methods that have the potential to replace the DPS process.