What is the consequence of selling an equine without the required negative test documentation?

The correct answer highlights the necessary protocol for ensuring the health and safety of both animals and humans involved in equine activities. If an equine is sold without the required negative test documentation, the horse will be isolated until it can be tested. This procedure aims to prevent the potential spread of infectious diseases that may affect other equines or, in some cases, impact human health as well. Isolation serves as a precautionary measure, allowing for proper assessment of the animal's health status before it joins a new environment or owner.

This approach not only protects the equine community but also aids in maintaining public health standards, as certain diseases can have serious implications if transmitted. The other options, while relevant to health and welfare concerns in the equine industry, do not directly address the immediate protocol enacted when the necessary documentation is absent. The focus on isolation emphasizes the importance of testing and confirmation of an animal's health status as a top priority in any equine transaction.