We have a duty to manage animals well and responsibly. Animal welfare is not a philosophy as such. It is a part of our culture, there are laws to protect animals, rules for the treatment of farm animals and many unwritten customs - all expressing the belief that animals should not be cruelly treated, and that people have a duty to look after them well. Many people who believe in animal welfare also believe that animals should be reared for food, killed if they are pests or be the quarry of sports such as fishing. There is no single definition of what is good or adequate animal welfare.
Animal rights is a philosophical viewpoint.
At the centre of the animal rights philosophy is the belief that animals must be included within the same system of morals that we apply to people. Therefore, a believer in animal rights would directly compare the needs of animals against the needs of people instead of putting the needs of animals second. He or she might decide that it is wrong to perform a medical procedure that sacrificed an animal, even if it saved a human life, because that would violate the animal's right to life. As with animal welfare, individuals' beliefs about animal rights vary a lot. The 1911 Protection of Animals Act defines cruelty as the infliction of 'unnecessary' suffering.