Unseen Suffering: A Critical Examination of USDA Reporting on Animals in Laboratories

Written by Kati Bertrand
July 2025

© iStock.com/Pijus Ash

Millions of animals are used in U.S. laboratories every year, but fewer than 1% are covered under the federal Animal Welfare Act (AWA) and overseen by the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS).¹ The vast majority—especially mice and rats, who make up most of the animals used—are unreported, uninspected, and unseen. This results in a profound underestimation of the actual number of animals subjected to experimentation in the U.S.

The AWA was the first federal law in the United States to regulate the use of animals in experimentation,² and was intended to serve as “[t]he law [that] establishes minimum standards of care that must be provided for animals with respect to, among other things, housing, handling, sanitation, food, water, veterinary care, and protection from weather extremes.”³ This mandate also includes conducting inspections of animal facilities, reviewing records, and collecting annual reports detailing animal use. But the USDA’s enforcement of this mandate is less than satisfactory: poor reporting practices and lack of transparency have created a system that falls short of fulfilling the AWA’s original intent.

The AWA has undergone several key amendments that, while appearing to expand or refine its scope, have ultimately made the law less enforceable.⁴ For example, the 1985 amendments⁵ mandated that research facilities establish Institutional Animal Care and Use Committees (IACUCs), provide opportunities for dogs to exercise, and take measures to promote the psychological well-being of nonhuman primates. However, the implementation of these standards has been inconsistent and largely left to institutions themselves. The 2002 amendment⁵ significantly narrowed the definition of “animal” by codifying the exclusion of species that constitute the vast majority of animals used in laboratories, including birds, rats of the genus Rattus, and mice of the genus Mus bred for research. This exclusion also extends to cold-blooded animals such as fish, reptiles, and amphibians, as well as horses and other farmed animals when used for research. While a 2023 amendment⁶ slightly expanded the definition of “animal” in the AWA to include birds not bred for research, it did nothing for the many other animals still excluded. Together, these changes have mostly weakened the AWA’s impact, creating a fragmented system that lacks both comprehensive coverage and meaningful oversight.

Numbers of Animals

An estimated 111 million rats and mice⁷ are used in experiments annually in the U.S., representing more than 99% of all animals used.¹ This means the AWA covers less than 1% of animals used in experimentation.

According to a recently published blog by Rise for Animals,⁸ 2,235,455 animals were kept in 1,014 facilities in 2024, a 40% increase from 2023. These higher numbers most likely come from expanded reporting. For example, labs were required to report the number of birds not bred for research, which accounted for 90,296 animals, and some facilities voluntarily reported 1,346,785 fishes used in experiments. Animals categorized as “other” accounted for 74.5% of all reported animals.⁸

Source: Rise for Animals, 2025.

But different calculations have been made by other groups. The National Anti-Vivisection Society (NAVS) reported smaller figures: 851,898 animals used across 776 facilities, including 88,872 birds reported for the first time.⁹ NAVS’ analysis indicated a 10% decrease in the reported use of AWA-covered species from 774,065 in 2023 (which did not include birds), as reported by USDA official numbers.¹⁰ On the other hand, Rise for Animals’ calculations show a 13% decrease from 2023 to 2024 when excluding the “other” category, which grew by 75%.⁸  

Reported Animal Use by Species
2023 vs 2024

• Dogs: The use of dogs in U.S. laboratories peaked at over 200,000 individuals per year in the late 1970s and early 1980s, then entered a 20-year period of decline.¹¹ The number of dogs used has remained relatively stable over the past two decades. Between 2023 and 2024, the use of dogs decreased by 9.5% from 47,239 to 42,752.
• Rabbits, Cats, and Guinea Pigs: The use of these species also decreased between 2023 and 2024, 11% for rabbits (125,030 vs. 111,277), 14.3% for cats (14,001 vs. 12,003), and 26.8% for guinea pigs (182,430 vs. 133,602).
• Non-Human Primates: Unfortunately, the use of monkeys has shown no downward trend.¹² In 2023, 107,812 monkeys were reported, and this number was only slightly smaller in 2024 (103,911), a mere 3.6% decrease.  
• Pigs: While publicly available USDA data did not provide a separate designation for pigs until 2002, their use has been trending downwards since then.¹¹ In 2023, 51,818 pigs were reported. This number dropped by 13% in 2024, to 45,082.  

Data collected from the APHIS website shows a decrease in the reported use of AWA-covered species, but this apparent reduction most likely comes from a shift in species preference, moving towards federally unregulated animals, which allows for less oversight and often results in poorer conditions for those individuals.

Category E Experiments

APHIS has established specific pain and distress categories that research facilities must use for their annual AWA reporting, providing a framework for classifying the level of discomfort animals experience.  

Category E is explicitly defined as procedures “involving accompanying pain or distress to the animals and for which the use of appropriate anesthetic, analgesic, or tranquilizing drugs would have adversely affected the procedures, results, or interpretation of the teaching, research, experiments, surgery, or tests.”¹¹ A fundamental, humane assumption guides this classification: “A procedure that would cause pain or distress in a human” is presumed to cause similar pain or distress in an animal.  

Examples of procedures, described exactly as written,¹³ falling under Category E:

• Paralysis or immobilization of a conscious animal
• Any Category D procedure for which needed analgesics, tranquilizers, sedatives, or anesthetics are withheld for justifiable study purposes
• Toxicological, microbiological, or infectious disease research that requires continuation after clinical signs are evident without medical care or that requires death as an endpoint
• Food or water restriction which reduces the animal’s weight by more than 15 percent of normal age-matched controls
• Certain types of forced exercise protocols that could reasonably be expected to cause distress or exhaustion
• Applying noxious stimuli that the animal cannot avoid/escape
• Exposure to extreme environmental conditions
• Long-term restraint (days to weeks)

NAVS calculated that 56,601 animals were subjected to painful procedures without pain relief in 2024, a decrease from 62,241 animals in Category E tests in 2023.⁹ But according to Rise for Animals, Column E numbers “showed mixed changes: numbers decreased significantly for cats and nonhuman primates but increased significantly for rabbits and sheep.”⁸

Source: Rise for Animals, 2025.

Just this quick glance at the current state of USDA reporting and oversight reveals a system in urgent need of fundamental, comprehensive reform: species exclusions, poor transparency, and a high number of experiments causing animal suffering. Poor reporting is not just a data issue, but a symptom of deeper, interconnected legislative, administrative, and ethical shortcomings.

With the shift in U.S. biomedical policy aimed at actively reducing and replacing the use of animals in experimentation, it’s critical that we have a starting point from which to measure progress. But the currently available data only allows for partial calculations and estimates.  

Until animals are no longer used in experiments, each individual used deserves to be counted and provided—at least—with the minimum welfare standards offered by federal regulations. It is arguably anti-science that the AWA definition of “animal” excludes most legitimate animals who are used in experimentation—including mice, rats, birds bred for research, and invertebrates. Experimenters and facilities should also be given established standards for handling, housing, and reporting the use of these species. Transparency must also be improved, as USDA often does not publicly release data on animal use in a timely and comprehensive manner. Without comprehensive data and consistent reporting standards, we lack the metrics necessary to evaluate progress toward reducing and replacing animal use. Inclusion and transparency will be essential to charting the scientific and ethical evolution toward this goal.

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1. Grimm D. How many mice and rats are used in U.S. labs? Controversial study says more than 100 million. Science. January 12, 2021. Accessed June 30, 2025. https://www.science.org/content/article/how-many-mice-and-rats-are-used-us-labs-controversial-study-says-more-100-million
2. National Research Council (US) Committee to Update Science M. Regulation of Animal Research. In: Science, Medicine, and Animals. National Academies Press (US); 2004. Accessed June 30, 2025. https://www.ncbi.nlm.nih.gov/books/NBK24650/
3. Animal Welfare Institute. Animal Welfare Act. Published 2024. Accessed June 30, 2025. https://awionline.org/legislation/animal-welfare-act
4. USDA National Agricultural Library. Animal Welfare Act. Accessed June 30, 2025. https://www.nal.usda.gov/animal-health-and-welfare/animal-welfare-act
5. Frasch PD. Gaps in US Animal Welfare Law for Laboratory Animals: Perspectives From an Animal Law Attorney. ILAR J. 2016;57(3):285-292. doi:10.1093/ilar/ilw016
6. Standards for Birds Not Bred for Use in Research Under the Animal Welfare Act. Federal Register. February 21, 2023. Accessed June 29, 2025. https://www.federalregister.gov/documents/2023/02/21/2023-03357/standards-for-birds-not-bred-for-use-in-research-under-the-animal-welfare-act
7. Carbone L. Estimating mouse and rat use in American laboratories by extrapolation from Animal Welfare Act-regulated species. Sci Rep. 2021;11(1):493. doi:10.1038/s41598-020-79961-0
8. More Animals Reported by Labs, Again. Rise for Animals. June 17, 2025. Accessed June 29, 2025. https://live-riseforanimals.pantheonsite.io/news/2024-data/
9. NAVS. U.S. Animal Use in Labs Drops Nearly 10% in 2024, NAVS Analysis Finds. June 12, 2025. Accessed June 28, 2025. https://navs.org/newsroom/u-s-animal-use-in-labs-drops-nearly-10-in-2024-navs-analysis-finds/
10. APHIS USDA. Annual Report Summary 2023. Published online October 28, 2024. Accessed June 30, 2025. https://www.aphis.usda.gov/sites/default/files/fy2023-research-animal-use-summary.pdf
11. National Academies of Sciences, Engineering, and Medicine. U.S. Department of Agriculture Statistics on the Use of Dogs and Other Animals in Research. In: Necessity, Use, and Care of Laboratory Dogs at the U.S. Department of Veterans Affairs. Vol Appendix B. National Academies Press; 2020. doi:10.17226/25772
12. Grimm D. Record number of monkeys being used in U.S. research. Science. November 2, 2018. Accessed June 30, 2025. https://www.science.org/content/article/record-number-monkeys-being-used-us-research
13. Animal and Plant Health Inspection Service. USDA Animal Care Tech Note: Categorizing Animal Pain or Distress in Research Facility Annual Reports. Published online July 2023. Accessed July 3, 2025. https://www.aphis.usda.gov/sites/default/files/ac-tech-note-categorizing-animal-pain-or-distress.pdf