USDA Pain and Distress Categories B–E

Q: Are purpose-bred laboratory mice and rats reported anywhere on Form 7023?

No. Rats of the genus Rattus and mice of the genus Mus bred for use in research, along with birds bred for research, are excluded from the Animal Welfare Act’s definition of “animal” and do not appear on this form at all, regardless of what pain or distress they experience in a study.

APHIS Form 7023, the annual report every USDA-registered research facility files, sorts every animal it covers into one of four columns — B, C, D, and E — by the pain or distress that animal experienced. Column B is animals not yet used. Columns C, D, and E rank the animals that were used, from no pain through pain that was relieved to pain that, for a documented scientific reason, was not. Getting an animal into the wrong column is not a paperwork slip: Column E requires a written justification attached to both the protocol and the federal report, and the distinction between D and E is the one IACUC reviewers and APHIS inspectors return to most often.

The five columns, in the form’s own words

Form 7023 defines each column this way. Column F is a check, not a judgment call — it has to equal C + D + E, and Column B is deliberately left out of that total.

Column	What it counts	Typical example
B	Animals being bred, conditioned, or held for teaching, testing, experiments, research, or surgery, but not yet used for that purpose as of the close of the reporting year.	A breeding colony’s adults and unweaned offspring, none of them yet assigned to a protocol.
C	Animals used in a study that involved no more than momentary or slight pain or distress — including no pain at all, and including animals given a sedative purely for restraint rather than to relieve pain.	Blood draws, injections, tattooing, or euthanasia performed under current AVMA guidelines (euthanasia performed correctly is defined as painless and reported here, not in D).
D	Animals used in a study that caused pain or distress, where that pain or distress was relieved with an appropriate anesthetic, analgesic, or tranquilizer.	Survival surgery under anesthesia; a terminal procedure where the animal is euthanized before it recovers.
E	Animals used in a study that caused pain or distress, where the appropriate drugs to relieve it were not used because doing so would have compromised the procedure, the results, or their interpretation. An explanation of the procedure and the reason the drugs were withheld must be attached to the report.	An untreated control group in a pain-mechanism study; toxicity testing where analgesia would mask the endpoint being measured.
F	Total of Columns C + D + E, by species. Column B is not added in.	—

Column A is not a count at all — it is where the facility lists the common names of the regulated species it is reporting on. Purpose-bred rats of the genus Rattus, purpose-bred mice of the genus Mus, and birds bred for research are excluded from the Animal Welfare Act‘s definition of “animal” entirely, so they never appear on Form 7023 at all — a fact that surprises investigators who assume “USDA-regulated” means every vertebrate in the vivarium.

The distinction that actually matters: Column D versus Column E

Both columns start from the same fact: the animal experienced pain or distress beyond the momentary/slight threshold that would put it in Column C. The entire question is whether an anesthetic, analgesic, or tranquilizer was used to relieve that pain or distress:

Column D — the drugs were used. This is where the large majority of surgical and invasive-procedure animals land, and it requires no special written filing beyond the protocol itself.
Column E — the drugs were not used, specifically because using them would have interfered with the science. A study on the pain mechanism itself, a toxicity or LD₅₀ endpoint that pain relief would confound, or a control group whose whole purpose is the untreated comparison, are the standard examples.

The National Institutes of Health’s own guidance for its intramural research program spells out how close the two categories can sit: in a described pain-control study, guinea pigs that received analgesia were reported in Column D, while genuinely untreated control animals in the same study, experiencing the same procedure, were reported in Column E — same protocol, same species, different column, because the drug either was or was not given. Column E is not a severity rating; it is a statement about whether relief was withheld, and why.

Reclassification can happen mid-study, too: if a Column C procedure turns out to cause more than momentary pain in practice, the guidance is explicit that the IACUC must be told, the protocol modified or halted, and the animal moved to Column E — not quietly left in C because that is where it started.

The Column E justification, and the search for alternatives that has to precede it

Two different documents get conflated here, and an IACUC reviewer will ask about both separately:

The alternatives search. Before a protocol can propose any procedure expected to cause more than momentary or slight pain or distress — which covers everything that will land in D or E — the principal investigator has to have considered alternatives to it, and provide a written narrative of the methods and sources used to determine that none were available. This is required by regulation, not by IACUC custom: 9 CFR 2.31(d)(1)(ii). The regulation does not name a specific database or a minimum number of years to search — that specificity comes from each institution’s own protocol form. What most PIs actually search against is the concept AWIC (the Animal Welfare Information Center, the USDA National Agricultural Library program the 1985 AWA amendments created for this exact purpose) organizes its guidance around: replacement, reduction, and refinement.
The Column E justification itself, which is a separate, narrower document: an explanation of the procedure that produces the pain or distress, and the specific scientific reason the anesthetic, analgesic, or tranquilizing drugs were not used. Form 7023’s own instructions require it attached to the annual report, and APHIS provides a dedicated form for it — Form 7023B — that most institutions also require attached to the underlying animal study protocol before the IACUC will approve it.

The alternatives search has to happen even when the procedure ends up relieved and reported in D. The Column E justification only gets written when it does not.

Who actually assigns the category

No single office decides this in isolation:

The principal investigator proposes the category as part of the animal study protocol, together with the alternatives-search narrative and, if applicable, the Column E justification.
The IACUC reviews and approves the protocol — and with it, the category — under 9 CFR 2.31(d)(1), confirming both that alternatives were genuinely considered and that a Column E withholding is scientifically justified rather than convenient. Where the IACUC finds that severe or chronic pain or distress cannot be relieved at all, the regulation requires euthanasia rather than a Column E entry that lets the animal continue.
The attending veterinarian has standing authority over the adequacy of veterinary care underlying that determination, though routine or non-protocol-related veterinary treatment does not itself change an animal’s pain category.
The institution’s compliance or animal-care office compiles every approved protocol’s column assignments, by species, into the facility-wide Form 7023 — a facility with more categories or species than fit on one page continues onto Form 7023A.
The Chief Executive Officer or another Institutional Official with legal authority to bind the facility certifies the completed report is true, correct, and complete, under 7 U.S.C. 2143, and that certification is what APHIS actually receives.

How the annual report gets filed

Every fact above eventually has to reach APHIS in one submission, once a year, for the federal fiscal year (October 1 through September 30):

What gets filed: Form 7023 itself (with 7023A continuation sheets as needed), plus a Column E explanation (Form 7023B) for every protocol reporting animals in Column E, plus a summary of any IACUC-approved exceptions to the standard care regulations, identifying the exception, the species, and the number of animals affected.
How it gets filed: APHIS now processes annual reports through an online portal rather than a mailed paper form. Submitting requires the facility’s USDA registration number and access code, plus a Login.gov account for whoever the facility authorizes to submit.
When: the regulatory deadline is December 1 of each year, covering the fiscal year that closed on September 30. APHIS’s own portal, confusingly, stays open through December 31 — but that is not an extension of the filing deadline, and a facility that treats “the portal is still open” as license to wait past December 1 is out of compliance for the days in between.
Who has to file at all: every USDA-registered research facility, and every federal research facility, even one that used no covered animals that year — a zero report is still a required report.

Where each of these requirements is written down

Requirement	Authority	Where to read it
Annual report obligation itself, and the CEO/IO certification	7 U.S.C. §2143; 9 CFR §2.36	7 U.S.C. 2143 / 9 CFR 2.36
Column definitions B through F	APHIS Form 7023 itself	APHIS Form 7023 (PDF)
Alternatives-search requirement before a painful procedure is approved	9 CFR §2.31(d)(1)(ii)	9 CFR 2.31
Written justification for withholding pain relief; mandatory euthanasia for unrelievable severe/chronic pain	9 CFR §2.31(d)(1)(iv)–(v)	9 CFR 2.31
Current online filing process, portal window, and forms in use	APHIS Animal Care	Submit Research Facility Annual Reports (APHIS)
Detailed column-assignment examples (Column B/C/D/E worked cases)	NIH Office of Animal Care and Use	Guidelines for Preparing USDA Annual Reports (NIH OACU)

What this page cannot tell you

Three things decide how a specific animal on a specific protocol gets classified, and none of them are answered by the general rule above:

Whether your IACUC’s protocol form asks for more than the regulation requires. 9 CFR 2.31(d)(1)(ii) requires a written alternatives narrative but not a named database, search-term list, or lookback period — your institution’s own form usually adds all three, and reviewers hold PIs to whatever the local form specifies, not just the federal minimum.
Whether your specific procedure is D or E once your IACUC has actually reviewed it. The category depends on the scientific reason pain relief was or was not used, and reasonable IACUCs disagree on borderline cases — that judgment happens in your protocol review, not in a general reference.
Who at your institution is authorized to submit the annual report through APHIS’s portal. The Login.gov account and facility access code belong to a specific designated person, and that assignment is an internal administrative decision this page has no way to know.

Checking this against the current guidance

The rule above is the general one. The answer for a specific protocol depends on which procedure, which species, and which IACUC’s own protocol-form requirements you’re working against.

Ask CASRAI: What does 9 CFR 2.31 require a principal investigator to document before pain-relieving drugs can be withheld from an animal placed in Column E, and how does an IACUC decide whether that documentation is sufficient?

It searches CASRAI’s indexed corpus of research-administration guidance and cites the passage behind each claim, so you can open the source and check it rather than take its word — and it says so when the corpus does not cover something instead of guessing. Two questions a day are free while you are signed out, no account and no card. Everything CASRAI publishes stays free to read.

Your first free question is the one in that link. Save the second for the part that depends on your own protocol — the specific procedure, your IACUC’s own alternatives-search requirements, or which of your species is even covered by the Animal Welfare Act in the first place.

Frequently asked questions

What does 9 CFR 2.31 require a principal investigator to document before pain-relieving drugs can be withheld from an animal placed in Column E, and how does an IACUC decide whether that documentation is sufficient?

The regulation requires a written justification, in the protocol, of why appropriate anesthetic, analgesic, or tranquilizing drugs were not used — tied to a genuine scientific reason the drugs would have compromised the procedure, results, or their interpretation. It does not specify a format or a level of detail; that judgment belongs to the reviewing IACUC, and standards vary between institutions.

Does Column E mean the procedure is unapproved or non-compliant?

No. Column E is a routine, expected category for legitimate research — untreated controls in pain studies and certain toxicity endpoints are standard examples in APHIS’s own guidance. It becomes a compliance problem only when the justification is missing, generic, or not genuinely tied to the science.

Are purpose-bred laboratory mice and rats reported anywhere on Form 7023?

No. Rats of the genus Rattus and mice of the genus Mus bred for use in research, along with birds bred for research, are excluded from the Animal Welfare Act’s definition of “animal” and do not appear on this form at all, regardless of what pain or distress they experience in a study.

Does an animal reported in Column B ever change category later without a new report?

Not within the same reporting year in a way that appears anywhere — Column B animals are, by definition, not yet used. Once a held or bred animal is assigned to a protocol, it moves to C, D, or E in whichever annual report covers the year it was actually used.

What happens if a facility uses no regulated animals in a given year?

It still has to file. APHIS’s own reporting reminders are explicit that the report is required even from a facility that held or used no covered animals during that fiscal year — a report with all-zero columns is still the required filing, not an exemption from filing.