Animal comfort is a primary concern in how experiments are conducted.
The researcher must explain why research procedures that might be painful are necessary and what will be done to keep the animals as comfortable as possible. Research may not proceed without this approval. Most of the time, either the experiment is not painful or else pain-relieving drugs are given as part of the research protocol. A few experiments do involve painful procedures because pain is being studied or drugs would interfere with the research. In such cases, scientists are morally and legally obligated to ensure that the procedures are necessary.