Originally Posted by Joie
This is not QUITE true, at least not in the US. While the horse can be REGISTERED with the ATA, it would not be considered a purebred, nor would it be eligible for inclusion in the OFFICIAL studbook. The percentage of thoroughbred or arab blood cannot be that high for the horse to be considered for Official Stud Book (OSB) approval. For example, if you have a OSB approved "purebred" Trakehner mare whose dam was a Preliminary Stud Book (PSB) approved thoroughbred, you cannot breed the OSB approved mare to an OSB approved thoroughbred or arabian stallion and have that resulting foal be eligible for OSB approval. The stallion cannot have a TB or Arabian parent.
Clear as mud?
No I get it :) My favourite stallion (recently deceased) was registered Trakehner (purebred) and Arabian Warmblood, and his dam was a registered Anglo Arab (and Anglos can ONLY have Arab/TB blood). I'm pretty sure there IS a minimum amount of Trake blood they have to have to be considered purebred, but it's less than 50% or this stallion wouldn't have been registered as a purebred.