I work in biomedical research. Many of the experiments that we do would certainly be more informative if we could legally perform them on humans, but this is not possible. So animals are substituted with the intent of transferring the successes to human trials. The animals are treated very humanely- in fact there are institutional standards and various laws (not sure if they are federal or state) to protect the animals that must be upheld. They are always supposed to be housed in special facilities with constant care, high-quality foods, extremely sanitary conditions, and access to good veterinary care. Sick and suffering animals are euthanized humanely, and some of the animals are adopted out later (we obtained four pet mice this way).
I hope this helps if you have concerns. I know this isn’t Church position, but since another person posted the CCC citations, I figured I’d expand a bit.