Which of the following is used to document an animal's record of ancestry?

The pedigree is a document that outlines an animal's lineage and ancestry, detailing the family history and bloodlines of the individual animal. This record is crucial in livestock management and breeding, as it provides information about the genetic background and potential traits that may be passed down through generations. Pedigrees are often consulted by breeders to assess genetic traits, heredity, and to make informed decisions regarding breeding practices.

Other options serve different purposes: a health certificate is used to verify the health status and vaccination history of an animal, a bill of sale is a legal document indicating the transfer of ownership from one party to another, and an inventory log is a record of all animals on a farm or ranch, typically used for management and tracking purposes. None of these documents provide a detailed account of an animal's ancestry, which is why the pedigree stands out as the correct choice.