Hi All,
Here is the excerpt from the American Simmental Association that will answer your question:
PARENTAGE
Dam's ASA registration number: This is a unique number assigned by the Association to a dam at the time she was registered. If the dam is not registered with ASA, then a permanent identification-not a name-year of birth and her percentage breeds such as 100 Angus or 1/2 Mix and 1/2 Hereford are required.Sire's ASA registration number: This is a unique number assigned by the Association to the sire at the time he was registered. The sire must be registered in the Simmental or Simbrah herdbook before a calf can be registered.
Breeders using sires of another breed can register calves as Simmental provided the other breed sire is registered with his breed association and then with ASA and the dam is a registered Simmental
Hope this helps you,
Kevin