Debates over the use of animals for research often center on the animals’ experience of pain. Animal welfare regulations require researchers (and instructors who use animals for educational purposes) to report whether the animals they use are subjected to pain and whether it is relieved by medication. When pain-relieving medication is not used during painful procedures, researchers and instructors must justify the reason – for example, by demonstrating that such medications would adversely affect their experiments or lessons. Reporting is not required for mice of the genus Mus and rats of the genus Rattus bred for use in research or for birds and aquatic species other than marine mammals. Here is a breakdown of the reported number of animals used by species, the number of those animals subjected to relieved and unrelieved pain, and the numbers not subjected to pain.
| Animal | Total Usage | With pain, relieved with drugs | With Pain, no pain-relief drugs | No Pain, No Drugs |
|---|---|---|---|---|
| Guinea Pigs | 213,029 | 63,889 | 33,652 | 115,488 |
| Rabbits | 210,172 | 81,303 | 5,996 | 122,873 |
| Hamsters | 145,895 | 34,204 | 48,015 | 63,676 |
| Nonhuman Primates | 71,317 | 29,413 | 1,395 | 40,509 |
| Dogs | 64,930 | 24,710 | 697 | 39,523 |
| Pigs | 53,260 | 40,911 | 770 | 11,579 |
| Other Farm Animals | 38,008 | 12,884 | 187 | 24,937 |
| Cats | 21,578 | 8,595 | 153 | 12,830 |
| Sheep | 13,271 | 8,223 | 65 | 4,983 |
| Marine Mammals | 126 | 10 | 0 | 116 |
| All Other Covered Species | 303,107 | 35,627 | 6,193 | 261,287 |
| Total | 1,134,693 | 339,769 | 97,123 | 697,801 |
Source: Annual Report Animal Usage by Fiscal Year, United States Department of Agriculture, Animal and Plant Inspection Service, July 2011 http://speakingofresearch.files.wordpress.com/2008/03/2010_animals_used_in_research.pdf; National Institutes of Health Office of Animal Care and Use http://oacu.od.nih.gov/ARAC/documents/Pain_and_Distress.pdf; USDA Pain Levels http://www.esf.edu/animalcare/documents/USDApainLevels.pdf;