Many definitions are used to describe animal welfare. The definition by the American College of Animal Welfare is that animal welfare “refers to the state of the animal.” Definitions often include the different aspects of animal welfare, as for the definition by David Fraser, which includes an animal's physiology, ability to perform species-typical behavior, and the animal's emotional state, where good welfare is a combination of satisfactory levels in all of these realms. Welfare is on a continuum and may be considered poor, adequate, or good.
The framework that formed the basis for modern animal welfare science is that of the “five freedoms," developed from the Brambell Report in the UK in response to the book Animal Machines by Ruth Harrison. The five freedoms are: freedom from hunger or thirst; freedom from discomfort; freedom from pain, injury, or disease; freedom from fear and distress; and freedom to express normal behavior.
Welfare is fundamentally something viewed from an individual animal’s perspective. It is a balance between an animal’s negative and positive experiences and reflects its ability to cope within its environment to obtain its needs.
Ethical issues must be separated from welfare concerns. Ethics are when one asks whether something should be done, not how it is done. Animal welfare science is a blend of science and ethics where ethical questions illuminate areas of societal concern and science elucidates the biological processes and the animal's responses. An example of an ethical issue is whether humans should be allowed to use animals in biomedical research, whereas animal welfare science provides information on how laboratory animals respond to the conditions they are experiencing.
Veterinarians can play different, yet integral, roles in improving animal welfare, from improving individual animal welfare during clinical appointments, to working with populations of animals in places such as laboratories, farms, and shelters.
Laws and regulations related to animal welfare are enacted either by federal, state, or local municipalities. Examples in the United States at the federal level include the Animal Welfare Act, the Fur Seal Act, and the 28 Hour Law. State and local laws can be more restrictive than federal laws, and examples include those regarding animal cruelty, breed-specific legislation, and specific housing requirements.
There are numerous international entities that promote animal welfare by providing a framework for international cooperation. The World Organization for Animal Health (OIE) provides international standards for animal welfare, including shipping, production systems, and slaughter.
There is no single measurement that can quantify the state of an animal’s welfare. Measurements are divided into animal-based measures and facility-based measures, with animal-based measures indicating how an animal is responding to its environment and facility-based measures assessing the environment itself. An example of an animal-based measure would be assessment of scratches or other skin lesions, whereas a facility-based measure would be measurement of the size of the pen. Measurements are made in multiple realms, including physiologic and behavioral measures, and assessment of the emotional state of the animal.
Physiologic measures include those that reflect the overall health of the animal such as mortality rates and lifespan as well as measurements of productivity (eg, milk production, reproduction rate), and disease incidence. Often, the hypothalamic-pituitary axis is used to determine an animal's stress response and the relevant glucocorticoid is measured for the species in question. Physiologic measures are a key part of welfare though they often lack valence. For example, glucocorticoids may rise after a painful procedure or after a positive social interaction, so measures such as behavioral and emotional responses must be added to get a well rounded assessment of an animal's welfare.
Behavioral measurements of welfare include those indicating how well an animal functions or how frequently an animal demonstrates a particular behavior. Behavioral indicators of good welfare include normal exploratory behavior, alertness, interaction with others, and play behaviors. Indicators of poor welfare include occurrence of stereotypic behaviors, abnormal fear behaviors, excessive aggression, behaviors directed toward an atypical object, and behaviors related to pain or illness. Frequency, duration, and intensity of the behaviors, and the number of animals in a population demonstrating these behaviors, give a quantitative evaluation of the welfare of an individual or population.
Measures of emotion in animals have often been thought of as controversial but progress continues to be made in this area. One way emotional states in animals are assessed is called cognitive or judgement bias. Animals are trained to a positive cue and a negative cue and then given an ambiguous cue. If the animal approaches the ambiguous cue, they are said to be in a positive affective state, whereas if they treat the ambiguous cue as negative, they are said to be in a negative affective state. This approach has been used to assess how animals respond to different situations, for example a painful procedure with and without pain relief, and has been used in many species (ie, from honey bees to pigs).
An area receiving more focus is the assessment of positive states in animals, not just the prevention of negative states. Positive welfare is when the animal can engage in rewarding goal-directed behaviors such as affiliative behavior between a mother and offspring. Other behaviors such as play are used as indicators of positive welfare.
Sometimes, improvement in one welfare measurement correlates to a decline in another aspect of welfare.
Intensive animal agriculture does not necessarily correlate with poorer welfare for the animal. The term “factory farm” is often used to describe a large, industrialized farm in which high numbers of animals are raised in confinement, often to maximize production efficiency while minimizing costs and protecting animals from disease and environmental extremes. Animals raised in these systems may have better welfare than those raised on small farms and farm size is not necessarily an indicator of animal welfare.
Feed additives, implants, and other substances are sometimes used to promote efficiency such as improving feed-to-gain ratio, or for increasing milk production. Use of some in-feed antimicrobials for the promotion of growth has been banned in the US in animals entering the food chain, although regulation against use of antimicrobials in intensive production systems could potentially decrease animal welfare by not preventing disease outbreaks. Their overuse, however, could promote development of resistant microbes and lead to reduced welfare. Overall, it is important to consider multiple aspects of an animal's welfare, along with the productivity of the animal, to understand the impact of such practices.
Farmed animals undergo a variety of procedures that can be classified as painful including castration, tail docking, and disbudding or dehorning. Castration is performed in many species to decrease aggression toward other animals and people, and to improve meat quality. Improving welfare could entail finding alternatives to castration or providing pain relief during and after the procedure. Alternatives such as a GnRH vaccine in swine, or maintaining lambs in same-sex flocks, eliminate the need for the procedure. Where alternatives do not exist, pain mitigation may be an option to improve welfare.
Dehorning,the removal of the horn, and disbudding, the removal of horn epithelium, are typically performed in cattle and small ruminants to prevent injuries to caretakers and other animals. The American Association of Bovine Practitioners released dehorning guidelines in 2019, recommending it be done as early as possible, using the least stressful technique for restraint, and using pain control for all methods, regardless of the animal’s age. To improve welfare, there are well defined and effective pain mitigation protocols for use in dehorning and disbudding, and the need for the procedure can be eliminated by the use of polled genetics.
One aspect of intensive animal production, compartmentalization of animal raising into age-specific facilities, may lead to more transportation episodes in an animal's lifetime. Appropriate transport vehicles and bedding, and humane handling and driving techniques are some things that can mitigate stress during transport. Animal slaughter facilities are inspected for animal welfare and, while such facilities are highly scrutinized, animal welfare is built into the protocols at inspected slaughter plants, from handling at unloading through the stunning and slaughter process. The AVMA has published guidelines on this topic.
Gonadectomy is performed to prevent pet overpopulation, to prevent medical conditions such as pyometra and some neoplasias, and to prevent and treat some problem behaviors. Recent studies demonstrate that gonadectomy in dogs correlates with an increased risk of some neoplasias and orthopedic diseases in some breeds, potentially with a higher risk if performed earlier rather than later in life.
In contemporary times, dogs have been trained using positive punishment and negative reinforcement. During recent years, there has been a growing body of research on the negative effects from using coercive training methods, including increased aggression and anxiety. One study of nearly 4,000 dog owners found that the use of positive punishment and negative reinforcement was related to an increased risk for aggression toward people when compared with the use of positive reinforcement and negative punishment. Owners of dogs visiting a veterinary behaviorist were more likely to select euthanasia of their dog if they had used punishment-based training methods or previously consulted with a nonveterinary behaviorist or trainer. Compared with the use of aversive training, the use of positive-reinforcement methods has been correlated with having a better-trained dog and with fewer stress-related behaviors.
All surgical procedures have the potential to cause pain via tissue manipulation. The ethical question is whether veterinarians should perform nonessential surgeries, such as tail amputation, ear cropping, devocalization, and declawing. There is evidence that some of these procedures, such as declawing, cause lifelong debilitation, especially if not performed correctly.
Horses are unwanted when owners are unable to provide appropriate care, if horses don’t meet expectations for racing or show, or if they have a problem behavior such as aggression. If there is no new owner or rescue organization to properly care for the horse, options include humane euthanasia (which is expensive when considering after-death care of the body) or slaughter. There are currently no federally inspected horse slaughterhouses in the USA. Horses must be shipped to another country for slaughter, necessitating significantly long trailer rides.
Soring refers to anything that causes pain resulting in an exaggerated gait. These include chemical irritants, burns, or lacerations on the distal aspect of a limb or something that causes pain to the hoof. Soring is most often associated with Tennessee Walking Horses. Often, results are amplified by placement of chains or other “action devices” and improper shoeing. By causing pain, the horse lifts its feet higher, resulting in a higher-valued gait, also called the big lick gait. Showing of sored horses is prohibited by the Horse Protection Act, which is enforced by the USDA.
Tail modifications include docking (amputation of the distal part of the tail), nicking (cutting tail tendons to cause an elevated tail carriage), and blocking (deadening tail nerves with alcohol injection to cause a limp tail carriage). Historically, docking was performed for safety while driving horses but now is only done for appearance. Nicking and blocking are only done for appearance.
Exotic and nontraditional pets can roughly be divided into domesticated and nondomesticated. Owner expectations may be different for a nontraditional pet, and owners may be less educated on the needs of a niche pet. Most welfare problems, especially of exotic pets, are related to husbandry issues. These include but are not limited to: diet; housing (space, substrate, location); veterinary care; and social interactions (with people as well as conspecifics).
Small mammals, such as rabbits, rats, mice, and guinea pigs, are social animals but vary in their ability to peacefully live with conspecifics in a small-cage environment. Psittacines are often kept individually in a too-small cage with little human interaction or environmental enrichment, even though they live in flocks and can fly miles per day in their natural environment.
The most basic discussion concerning animals in zoos and aquaria is whether wild animals should be held in captivity. One argument in favor of captivity is to use these animals to educate the public on conservation by providing an engaging way to learn about the topic. Zoos and aquaria must balance how much visitors learn with the welfare of wild animals in captivity. Accrediting agencies, such as the Association of Zoos and Aquariums (AZA), can hold member facilities to a higher standard of welfare. The AZA has worked to create species-specific animal care manuals that describe best practices for keeping various species of wild animals in captivity.
Captive breeding programs and the Species Survival Plan are used to help assure perpetuation of species, especially endangered species. An ethical question is whether these animals can, or should, be released into their historical habitat and whether this habitat is protected or even exists. Some species have successfully been reintroduced into protected environments, such as the California Condor and Gray Wolves into their historic habitats. Other species may never be able to be reintroduced safely into their original habitat.
Environmental enrichment is when the environment is amended in ways that are important to the animal and allow it to more fully express its species-specific behavioral repertoire, thereby providing environmental stimuli necessary for optimal physical and emotional wellbeing. It can encourage natural behaviors by having animals engage with additional items in their limited environment, and it can provide them the power and perception of choice. It is not a substitute for poor management or enclosure design, and it cannot compensate for substandard care. There is much research into the positive effects of enrichment on the welfare of animals, not limited to captive wildlife.
While there are discussions about the ethics of using animals in research, in general, people are in favor of using nonhuman animals if an animal's welfare is good and the research is important. A cost-benefit analysis is typically done to determine whether such research should be done, although it should be noted that the costs are borne by the nonhuman animals while the beneficiaries are humans.
In The Principles of Humane Experimental Technique, the authors proposed the concept of the Three Rs for research, which stand for replacement (substituting nonanimal methods when possible), reduction (improving experimental design so that fewer animals are needed), and refinement (improving animal husbandry, reducing stress, and other methods for enhancing animal welfare). These principals form the foundation for animal welfare during the use of animals in biomedical research.
Providing for an animal's ability to perform species-typical behaviors improves its welfare. Much research has focused on using environmental enrichment for laboratory animals, demonstrating positive effects on animal welfare. Simple suggestions include provision of hiding places, "walls" within a cage to allow for thigmotaxis, the ability to eat via food-dispensing objects, and social housing. Environmental enrichment should be species-specific and based on the preferences and motivations of the species in question. Cage size matters, but a larger cage without any other improvements may not provide a measurable improvement in welfare.
Euthanasia is defined as a good death. The AVMA has published guidelines on euthanasia (see also Euthanasia of Animals) which detail the methods and agents appropriate for different species. One should consider not only the method and the agent but also the handling technique and the post-euthanasia disposal of the body. There are other factors, such as human safety, that may dictate the practicality of implementing a method of euthanasia. Euthanasia methods should be rapid and minimize fear and distress for the animal. The timeliness of euthanasia will also have an impact on animal welfare.
The term slaughter is used when an animal is killed for human consumption. Stunning methods vary by species and the method is usually performed before exsanguination except where there are exemptions for religious slaughter.
Depopulation is putting to death large numbers of animals in response to a public or animal health emergency. The AVMA published guidelines for these procedures.
Free-ranging and feral animals are either domesticated and escaped from their environment or descended from owned animals and sometimes considered "wild." Feral cats and free-roaming horses are at the forefront of debate. The welfare of the population is balanced with the welfare of other animals affected by the presence of the feral animals. Feral cats have been estimated to kill up to 4 billion songbirds annually in the USA, along with up to 22 billion small mammals. Feral horses compete with each other and native wildlife for limited resources on federal lands, primarily in western states of the USA. Horses are captured and are either neutered and returned to the wild, adopted, or kept in longterm holding facilities.
Welfare of rodeo animals is impacted by intense physical exertion, such as in calf-roping, barrel racing, and cutting. Bucking horses and bulls can subjected to physical manipulation, such as by flank straps. Calf-roping and steer tripping are other events that can lead to injuries. Charreadas are Mexican rodeos that have other events that are inherently more dangerous, such as horse tripping and steer tailing.
Handling during wild animal interactions, such as at roadside zoos and traveling animal shows, can result in the potential passing of zoonotic diseases. These facilities, although regulated by the USDA, are not typically overseen by the Association of Zoos and Aquariums. Therefore the risk for inappropriate handling and husbandry is high.
Animal use in circuses has come under greater scrutiny, resulting in some, but not all, circuses eliminating elephants from their shows. Large cats and other animals remain, and their husbandry and training techniques are sometimes questionable.
Cities, counties, states, and the federal government have various laws outlawing animal abuse and neglect. Veterinarians in some states are mandated reporters for animal abuse and/or neglect; even if not mandated, it is a veterinarian's responsibility to help protect animals, based on the veterinary oath.
Animal fighting, including dogfighting and cockfighting, are illegal in the United States yet remain popular in some areas. Animals are kept in poor conditions and are sometimes given illegal drugs to enhance their fighting ability. Fighting cocks are outfitted with metal spurs or knives to injure the other bird. Animals often fight to the death.