Although it is possible to formulate more robust moral principles than "animals should not be made to suffer unnecessarily," there are significant grounds for doubting these more robust principles. But the principle that underlies the dictum regarding unnecessary suffering is generally recognized as valid since denial of it implies that we can do whatever we want with animals. This conclusion is usually considered unacceptable. A determination of any particular instance of suffering is necessary or unnecessary must be based on analysis of the seriousness of the act's purpose that involves the suffering of animals and its relative avoidability, as well as more concrete concerns like costs and availability of resources for a given community. We can conclude, with reasonable certainty, that animals are suffering by observing changes in physiological and behavioral factors similar to the changes that tell us other humans are in pain. Further, the conclusion that any animal is suffering is sound, according to scientific methodology, because this hypothesis is usually the best available explanation for the observed alterations in physiology
Hurnik, Frank and Lehman, Hugh
"Unnecessary Suffering: Definition and Evidence,"
International Journal for the Study of Animal Problems: Vol. 3:
2, Article 16.
Available at: https://www.wellbeingintlstudiesrepository.org/ijsap/vol3/iss2/16