Thanks, Ross, for your thoughtful comment. I hope it alleviates your concerns a bit when I tell you that most experimental designs with mice do not require euthanization. Ethics board approvals are required for all experiments with animals. No positive ethics vote, no experiment, no publication. Researchers also work on methods to replace animal experiments with experiments on an "organ on a chip", that is experimenting with lab-grown organ cells (such as liver cells or brain cells, for example). Unfortunately, we are not yet in a position where we could do it completely without animal experiments.

To think about it, the experiments I referred to in my post, would be entirely needless if it were not for the couch potato lifestyles that most people self-select, and with which they drive themselves into a diseased older age.