Finally, the ethical implications of linking behavior and veterinary science are profound. The veterinary oath commits professionals to the "protection of animal health and welfare," and welfare is impossible without considering mental state. A physically healthy animal that is chronically anxious or confined in a barren, non-stimulating environment cannot be considered to have good welfare. The veterinary professional is now seen as an advocate not just for bodily health, but for the animal’s "telos"—its nature and the opportunity to perform its species-typical behaviors. This has led to science-based guidelines for everything from the housing of laboratory animals (requiring enrichment) to the management of livestock (providing rooting material for pigs, perches for hens) and the care of companion animals (prescribing daily exercise and mental stimulation). The veterinarian’s role has expanded from healer to architect of a life worth living.