Which portion of the statement about the Jockey Club Registry is untrue?

The statement that the Jockey Club Registry excludes Quarter Horses from embryo transfer is correct and clarifies a key aspect of the organization's breeding regulations. The Jockey Club focuses on the Thoroughbred breed, and embryo transfer is a technique that is indeed allowed for Thoroughbreds under specific guidelines. However, the regulations governing embryo transfer can differ among various breeds, and it may not specifically apply to Quarter Horses as the Jockey Club does not have authority over them.

In terms of the other statements, the Jockey Club has restrictions regarding artificial insemination. While it is commonly associated with Thoroughbreds, the organization does not permit artificial insemination in the traditional sense as it does for other breeds, which corroborates that it is not as commonly accepted as the statement suggests. Passage of breeding regulations can also be complex and subject to scrutiny rather than being easily enacted. Thus, recognizing these specifics helps affirm that the assertion regarding Quarter Horses and embryo transfer is indeed the untrue portion of the statement provided.