A scientist once confided in me that he became a scientist because as a child he really liked lizards, but as a scientist, he spends much of his time murdering lizards. :-/
Everyone involved has to confront this reality on their own, come to terms with it, and figure out the line where they're willing to meet it. All the researchers I've known have cared deeply about the welfare of the animals, despite sometimes doing terrible things to them for science. They worked to limit their suffering and dispatch them as humanely as possible. Many rationalize it by comparing to the food system, which raises and slaughters orders of magnitude more souls, and keeps people living, but does not discover or record as much new knowledge as science.
As far as I know it’s one of the few fields with authorities that can block animal cruelty on ethical grounds through ethical review boards (mandatory Institutional Animal Care and Use Committees in the case of federally funded research).
Researchers must submit detailed protocols describing exactly what they plan to do, how many animals they’ll use, what procedures will be performed, how pain and distress will be managed, and why alternatives like cell cultures won’t work. There’s a whole framework called the 3Rs: replace animals where possible, reduce the number used, and refine procedures to minimize suffering.
Science is the wrong tree to go barking up, especially given the impact of the research overall, compared to clothing or food or other animals products.
Ethics rubrics for animal studies and institutional review boards for same are definitely an area academia is doing better than most other human endeavors. I didn't mean to imply otherwise. More to emphasize the intense moral introspection each of the researchers I've known who have done animal studies have had to do about it.
> This work did not require ethical approval. We minimized the number of animals used in the experiment and kept manipulations to a minimum.
edit: formatting
We do it because we lack better methods. Cart before the horse, since those better methods are often derived from cruel research, but that's the reason.
If we had a ray-gun to zap a bug with that gave us a perfect accurate reading of lactate levels within it we wouldn't resort to freezing the thing and then grinding it to dust.
Add to this that people in the western world eat way more than they need. You only have to think of that all-you-can-eat restaurant.