Lab animals are always euthanized after the experiments are done. They don’t turn these tortured animals into pets.
It is true that lab animals are always euthanized after experiments are finished, at least at some point. Often they are sedated during the experiments. Very often the larger lab animals like dogs and cats were purchased from shelters that are too full. Those animals were going to be euthanized anyway, which is an unpleasant truth.
Mice, rats, hamsters, and guinea pigs are often bred by companies specializing in that type of thing, for a specific purpose. Most all of these are euthanized after the experiment is finished.