USDA Pain Categories

The Classification System

The United States Department of Agriculture requires every research facility to report its animal use under the Animal Welfare Act using a column-based pain classification system. Each animal used in research is assigned to 1 of 3 reporting columns based on the level of pain or distress involved:

• Column C — animals used in procedures that involve no pain, distress, or use of pain-relieving drugs. Examples: breeding colonies, behavioral observation, some blood draws.
• Column D — animals used in procedures that involve pain or distress, where appropriate anesthetics, analgesics, or tranquilizers are used. Examples: most surgical procedures, many toxicology studies, cardiovascular telemetry implantation.
• Column E — animals used in procedures that involve pain or distress, where the use of pain-relieving drugs would interfere with the study. This is the most controversial category. The animal experiences unrelieved pain or distress by design.

FY2024 Dog Numbers

The most recent USDA APHIS annual report provides the following figures for dogs across all Column categories:

• Column C — 27,909 dogs
• Column D — 12,176 dogs
• Column E — 410 dogs

The total — 40,495 dogs — represents all dogs reported under the Animal Welfare Act for that fiscal year. This number includes beagles and other breeds, though beagles constitute the vast majority of dogs in pharmaceutical and chemical testing.

The Column E Problem

Column E is where regulatory language meets physical reality. A Column E classification means that a dog experienced pain or distress and was deliberately denied relief because providing it would compromise the scientific objectives.

• 20% increase — Column E dog numbers rose from 375 in 2022 to 450 in 2023, a 20% increase in a single year.
• IACUC approval required — every Column E protocol must be specifically reviewed and approved by the facility's Institutional Animal Care and Use Committee. The IACUC must determine that the scientific justification outweighs the animal welfare cost.
• Written justification — facilities must provide a narrative explanation for why pain relief could not be used. Common justifications include: analgesics would alter metabolism of the test compound, sedation would confound behavioral endpoints, or the study specifically measures pain responses.

The approval process is not independent. IACUCs are composed primarily of facility employees and affiliated scientists. External, unaffiliated members are required but constitute a minority of the committee.

What Column E Looks Like

Column E procedures on dogs include but are not limited to:

• High-dose toxicology studies — where the purpose is to observe toxic effects at doses that cause overt suffering (vomiting, seizures, organ failure) and where analgesics would alter drug metabolism.
• Pain research — where the endpoint is the dog's pain response itself.
• Certain immunological studies — where immune suppression makes pain management medically complicated.
• Terminal procedures without full anesthesia — though these are less common under current standards.

The 410 dogs in Column E in FY2024 each experienced documented, unrelieved pain or distress. The actual number of dogs experiencing significant suffering is almost certainly higher — the boundary between Column D and Column E depends on subjective assessment and institutional culture.

The EU Comparison

The European Union uses a parallel severity classification system under Directive 2010/63/EU. Rather than a 3-column system, the EU classifies each individual procedure into 4 severity categories:

• Mild — 73% of all dog procedures
• Moderate — 23% of all dog procedures
• Severe — 3% of all dog procedures
• Non-recovery — less than 1% (animals anesthetized and never regain consciousness)

The EU system is more granular and applies to each procedure rather than to the animal's overall experience. A dog subjected to both a mild and a severe procedure is counted in both categories. The EU's "severe" category roughly corresponds to USDA Column E, though direct comparison is imprecise.

The EU's 3% severe classification represents a larger absolute number of dogs than the USDA's Column E, reflecting both the EU's larger research dog population and different classification criteria.

Limitations of the System

The pain classification system has fundamental limitations:

• Self-reporting — facilities classify their own animals. There is no independent verification of whether a procedure that causes significant distress is reported as Column D or Column E.
• Subjectivity — the distinction between "pain relieved" (Column D) and "pain unrelieved" (Column E) depends on judgment calls about whether analgesics adequately controlled suffering.
• Cumulative effects ignored — a dog gavaged daily for 12 months, bled repeatedly, housed in isolation, and ultimately killed is classified based on the single worst procedure, not the totality of its experience.
• Death is not pain — euthanasia itself is not classified as painful if performed according to AVMA guidelines, even though the necropsy that follows and the life that preceded it may involve extensive suffering.

The numbers tell us something. They do not tell us everything.

Sources

1. 1.USDA APHIS Annual Reports, FY2022-2024. Official reporting of animal numbers by pain classification category under the Animal Welfare Act.
2. 2.Welfare Outcomes, 2023. Analysis of USDA pain category trends, IACUC oversight patterns, and cross-year comparisons.
3. 3.EU Statistical Report, 2022. Severity classification data for dogs used in scientific procedures across EU member states.