Which of the following is required for sheep to be sold at federally approved interstate livestock auctions?

The requirement for sheep to be sold at federally approved interstate livestock auctions includes the presence of a Brucellosis tag. This tag serves as a crucial identification tool that indicates the animal has been tested for Brucellosis, a contagious disease that can significantly impact livestock health. The presence of the tag assures buyers that the sheep are free from this disease, which is particularly important for maintaining herd health and preventing the spread of infections.

While there are other forms of identification and health documentation relevant in livestock trade, such as health certificates or owner's identification, a Brucellosis tag is specifically mandated for interstate movement to ensure that animals are not carriers of this disease. This requirement supports efforts to control and monitor the health of livestock across state lines.