All About Animals Used In Research & Animal Testing

There are differing, conflicting, and overlapping perspectives in the ongoing international conversation about how animals are used in research and animal testing.

Some people believe that no animal should suffer pain or distress for the sake of human beings’ welfare. Some believe certain animals can be used on the condition that steps are taken to avoid unnecessary pain or suffering. A third group thinks that human need outweighs that of any other animal.

The use of animals for testing products and procedures has taken place for hundreds of years in dozens of countries. Over time scientific advances gave people a greater appreciation of the sentience of animals and an understanding that they have the capacity to suffer just as people do.

READ ALSO: Why Do Animals Gravitate Towards Me?

That led to a growth in movements advocating that animals should be spared unjustified pain, which in turn informed political debate and introduced laws to offer some level of protection.

Table of Contents

How many animals are used for research?

Legislative and regulatory frameworks regarding the treatment of animals vary in different countries and regions. For example, Canada, the European Union, and the UK each provide greater levels of protection for mice, rats, fish, and birds bred for research than does the United States.

The Animal Welfare Act (AWA) does not apply to those animals in the US, so their treatment is not regulated, and their numbers are not counted. The American Anti-Vivisection Society estimates that 93% of animals used for research and testing fall into this category.

If that estimate is correct, then considering the number of animals cited in the US Department of Agriculture’s latest report, the total number of animals used in research in the United States tops 11 million.

Speaking of Research (SR), an organization advocating the use of animals for laboratory testing and research puts the figure at somewhere between 10 and 25 million. The Humane Society of the United States concurs with the upper end of that range.

People for the Ethical Treatment of Animals (PETA) proposes the significantly higher figure of 100 million animals, whilst research published in Scientific Reports estimates the true figure could be as high as 111 million individuals.

RELATED: 47 Sea Shepherd & Whaling Facts No One Is Telling You

Which animals are used the most?

Guinea Pig Posing
Guinea Pig Posing

Commentators on all sides of the debate agree that in the United States, just as in most other nations engaged in animal testing and research, mice and rats are used in far greater numbers than any other animals. However, due to their use (and birds, fish, and frogs) not being regulated by the AWA, nobody knows precisely how many. Estimates for the proportion they comprise of all tested animals vary between 85% and 99.3%.

The latest USDA report mentioned above states that 797,546 regulated animals were used in US laboratories in 2019. This is a slight increase from previous years.

For some people, it will come as a surprise to learn just how many other animal species are used for testing. Of regulated animals, the proportion of each type used in testing was as follows:

  • Guinea pigs: 22.3%
  • Rabbits: 17.9%
  • Hamsters: 12.3%
  • Nonhuman primates: 8.6%
  • Dogs: 7.3%
  • Pigs: 6.4%
  • Cats: 2.3%
  • Sheep: 1.8%
  • All other covered species (including horses, goats, gerbils, bats, ferrets, and chinchillas): 20.7%

What about pain?

Animals used in testing and research are also categorized according to whether they were subjected to pain beyond a certain duration and intensity. If so, whether they were administered drugs for pain relief. Over one-third (34.5%) of regulated animals underwent physical pain during testing. Of those, almost one-fifth (18%) were not given any form of pain relief.

RELATED: Do Lobsters Have Brains, Feel Pain or Have Emotions??

No measurements or categorizations of emotional or psychological distress are taken. Whilst the AWA imposes a duty to ensure the environment provided to nonhuman primates is adequate to promote their psychological well-being, it makes provision for this to be withdrawn if doing so serves a research purpose.

Animals that aren’t covered by the AWA (mice, rats, birds, frogs, and fish) can be subjected to pain during testing without any legal consequences for the researchers.

Where do research animals come from?

Most animals tested in laboratories are purpose-bred to be used in experiments. The Department of Agriculture categorizes those who sell animals for this purpose as class A dealers. Class B dealers sell animals to laboratories after acquiring them from auctions, newspaper advertisements, or animal shelters. Animals are often taken from the wild include monkeys, birds, rats, and mice.

What happens to animals after experimentation ends?

In sporadic cases, animals are placed in a sanctuary; most are killed when testing ends. It is not unusual for animals to die during an experiment, either by accident or design. The lethal dose 50 (LD50) test is designed to determine the quantity of a substance that kills 50 percent of the test subjects.

Types of testing conducted on different animals

Mice and rats

As they are not protected under the AWA, it is unknown how many mice and rats experimented each year, but estimates range from 10 million to 100 million. The lack of protection they are afforded makes it likely they are subjected to pain more often and to a greater extent than other animals used for research.

They are also exposed to possibly the broadest range of test conditions, for example, being bred to be genetically predisposed to suffer from debilitating conditions such as cancer, a compromised immune system, obesity, or paralysis.

Their skulls get drilled into invasive brain experiments; they are electrocuted or dropped onto hot plates to test pain reflexes and undergo psychological experiments to examine how they react to terror, depression, and anxiety.

Guinea pigs and hamsters

Two of the most commonly used regulated animals, in 2019, over 180,000 guinea pigs and more than 98,000 hamsters were tested on. Together they constituted over 81% of the animals subjected to pain without any drugs for relief.

Guinea pigs are largely used for tests into the toxicity of cigarettes, alcohol, and drugs, examine spinal cord injuries, and study infectious diseases. Hamsters are frequently used to study cancers, brain diseases, heart problems, and kidney malfunction. Most die after suffering excruciating pain.


Of 142,000 rabbits used in experimentation, over 37% were subjected to pain. Rabbits are convenient for testing not so much for their similarity to humans but because they are easily restrained and have a rapid reproduction cycle.

Rabbits are usually used for painful corrosiveness tests on eyes and skin, starvation studies, and experiments into the vulnerability of pregnant females and their embryos. If they do not die during research, they are killed.

Nonhuman primates

More than 68,000 primates were used in experiments in 2019, and over one-third (35.9%) were inflicted with pain. Despite being the closest relatives to humans amongst the animals used for research and those we know feel a range of emotion and physical pain in a similar way to ourselves, primates are used in a broad range of tests.

Often born in laboratories, primate babies may be permanently separated from their mothers within days of birth for maternal deprivation studies. Further, primates will be subject to invasive brain experiments, vaccine and pharmaceutical tests, military experiments, and assorted psychological and emotional torture forms.

Even in the absence of specific tests designed to induce it, primates undergo psychological damage akin to that which afflicts humans exposed to abduction, deprivation, incarceration, and despair: they can drift into self-harm, despair, depression, and insanity.


The latest USDA figures reveal that over 58,000 dogs were used in laboratory testing in 2019, with over 27% being subjected to pain during testing. They are usually purpose-bred in laboratories or by private companies and are sometimes genetically manipulated to have cancer or human heart or lung diseases.

Dogs are also used in painful and debilitating toxicity studies in which they are force-fed or injected with pharmaceuticals, pesticides, and household chemicals. Dogs can be forced to run until the point of collapse, at which point they are killed, and the damage to the heart is examined, whilst pups bred with degenerative eye diseases are killed after they go blind.


Of over 50,000 pigs used in research, more than three-quarters were used in experiments involving pain. To make it easier to house and feed them, smaller pigs are often bred through genetic manipulation and selective breeding.

They are then used to test alcohol and drug use, burn studies, organ toxicity, cystic fibrosis, and xenotransplantation experiments. Pigs can be afflicted with respiratory, kidney, or bladder diseases, diabetes, or nutritional deficiencies.


As a comparatively large amount is known about their neurology, cats are often used to study spinal cord injury, vision, hearing, and sleep deprivation. They can also be used to investigate other conditions affecting humans, particularly genetic disorders, cancers, and Parkinson’s disease.

As cats can contract feline immunodeficiency virus (FIV), they are frequently used in research into HIV and AIDS even though critics pointing out that findings are of little utility due to differences between the feline and human forms of the condition. Almost 30% of cats underwent painful testing in 2019. Cats are usually euthanized after experimentation has concluded.

In conclusion

Whilst debate continues to rage over the efficacy and ethics around animal experimentation, few doubt that it is an anomaly for animals with just as much capacity to feel pain and suffering as those covered by the AWA not to be protected by it. Some observers add that the overwhelming majority of work conducted in animal research and testing does not produce readily or reliably applicable results to humans.

Leave a Comment