Humans have generally accepted that the suffering of other humans should be alleviated.
But this has not always been so.
Throughout history, groups of humans have defined members of other groups as less than human and therefore not worthy of compassion. This has been perpetuated by language and cultural barriers that prevented one group from recognizing the humanity of the other. This same form of thinking has prevented humans from accepting the cognition of other species. We still suffer from profound blindness regarding the emotional experiences and suffering of other creatures. Just as humans allow their inability to communicate with other human groups to justify the suffering of those groups, we ignorantly allow our inability to have verbal conversations with other species to justify placing no value upon their suffering. This is, to some extent, understandable, but is fundamentally wrong.
Unfortunately scientists have allowed this blindness to guide their actions for far too long, believing that human suffering is more important than the suffering of other species, thereby deliberately inflicting pain upon lesser creatures in the name of alleviating human suffering. This might have been morally justifiable before the considerable advancements of science that have occurred, but it is no longer justifiable. If suffering must occur in order to alleviate suffering, human beings should volunteer to experience that suffering- it should not be inflicted upon anyone or thing who has not chosen to take part in such research.