According to Peter Singer (a utilitarian philosopher), the morally appropriate action is the one that will maximize the interests of those affected.
Singer argues that it is necessary to weigh any adverse effect on animals’ interests from human actions in assessing the consequences of our actions. Other utilitarianists who think otherwise have failed to do this because of species bias (speciesism).
Singer suggests that the only way to justify animal testing is to maintain that species differences alone justify the harm inflicted on animals. However, this is equal to saying that differences in race or sex alone justify differential treatment among humans.
Overall, Singer’s utilitarian theory diverges from the classic utilitarian theory. From Singer’s perspective, utilitarianism considers animal testing (and the suffering that it causes in animals) unethical.