Which blood collection technique requires justification and is considered controversial?

The technique of tail transection is considered controversial and requires justification primarily due to ethical and welfare concerns associated with the procedure. Tail transection involves the removal of a portion of an animal's tail, which can cause significant pain and distress. This practice is viewed critically within the fields of veterinary medicine and animal ethics, as it may not be necessary for research purposes and alternatives should be considered whenever possible.

In laboratory settings, ethical guidelines often emphasize the importance of minimizing animal suffering and refining techniques to be as humane as possible. When tail transection is proposed as a blood collection method, detailed justification is required to demonstrate that the benefits of such a procedure outweigh the potential harm to the animal. This includes establishing that there are no viable alternatives that could achieve the same scientific objectives with less or no suffering.

Other blood collection techniques, while they also have their own considerations, do not typically carry the same weight of ethical debate as tail transection. For instance, cardiac puncture and retro-orbital blood collection can be controversial as well, but they are often justified in specific research contexts where the need for quality samples outweighs the risks involved, provided they are performed by trained personnel. Saphenous vein sampling is generally considered a less invasive technique and thus tends