 A 4-tier classification system was also introduced in place of a pass/fail system, in order to list animals on the studbook that do not meet the breed standard, with an aim to improve the genetic diversity of the breed.There is also a supplementary section in the Horse Sport Ireland studbook in order to recognise horses which may be primarily registered as Irish Sport Horses, but conform to the standard of the Irish Draught.The breed standard is defined in each country by the respective registry, although there have been efforts to harmonize standards between countries.