In 2024, HSI updated the studbook rules to enable certain mares, who have been deemed as being descendants from rare or threatened bloodlines, to automatically attain Class 1 upon presentation for linear profiling at an inspection. To attain an automatic Class 1 in 2024, the mare must have a mean kinship less than 1%, a Thoroughbred blood percentage less than 12.5%, a pedigree completeness index at generation 4 of 1, and an inbreeding % less than 6.25%. The studbook will contact the breeders of the mares who meet the criteria to attend inspection for studbook classification.

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