What percentage of animals that scientists have tested died this year?

There is no simple answer to this question, what happens to an animal after the experiments depends on what was done to them. A number of the animals will go onto be used in other experiments and even a few of them may end up in a loving home. Occasionally cats and dogs from testing are adopted out to families and some of the primates used end up on wildlife reserves or in zoos, however this is not typically the case and usually only happens to animals that were used in behavioral as opposed to medical studies. Some experiments require the animal to be euthanized for sample collection or post-mortem examination. Even when the animal is not required the be euthanized side affects of the experiments have made the animal unsuitable for either further experimentation or life as a household pet.