What activity would disqualify an animal from USDA category D?

The correct answer highlights a significant ethical and regulatory consideration in the treatment of animals used in research. In USDA category D, animals are subjected to potentially painful or stressful procedures but are managed in a way that aims to minimize suffering. This includes providing appropriate pain relief and care following procedures.

Allowing animals to die without pain relief directly contradicts the humane treatment standards required for category D. Such practices would indicate a blatant disregard for animal welfare and violate the principles established by the Animal Welfare Act and Institutional Animal Care and Use Committees (IACUC). Therefore, any study that permits animals to die without administering appropriate pain remediation disqualifies those animals from being classified within this category.

In contrast, the other options involve procedures where the animals receive anesthesia, which mitigates their pain and distress, thus keeping them compliant with the guidelines of USDA category D. This distinction reinforces the importance of not only recognizing potential pain or stress but also the ethical obligation to manage and alleviate it as part of responsible animal research practices.