# The Animals (Scientific Procedures) Act 1986 (Amendment) Regulations 2026, Schedule: Severity of procedures


“Schedule 2AA
Severity of procedures
Section 5BA(7)
Part 1
General
1 This Schedule contains descriptions of procedures assigned to a particular category of severity on the basis of factors relating to the type of procedure only.
2 Part 2 of this Schedule contains a list of procedures categorised as “mild”.
3 Part 3 of this Schedule contains a list of procedures categorised as “moderate”.
4 Part 4 of this Schedule contains a list of procedures categorised as “severe”.
Part 2
Mild procedures
5 The administration of anaesthesia except for the sole purpose of killing.
6 A pharmacokinetic study where a single dose is administered, a limited number of blood samples are taken totalling less than 10 per cent of circulating volume and the substance is not expected to cause any detectable adverse effect.
7 The non-invasive imaging of an animal with appropriate sedation or anaesthesia including, in particular, magnetic resonance imaging.
8 A superficial procedure including, in particular—
(a) ear and tail biopsies;
(b) non-surgical subcutaneous implantation of mini-pumps or transponders.
9 The application of external telemetry devices that cause only minor impairment to the animal or minor interference with normal activity and behaviour.
10 The administration of a substance where—
(a) the substance has no more than a mild impact on an animal,
(b) the volume of the substance administered is within appropriate limits for the size and species of the animal, and
(c) the substance is administered by any of the following routes—
(i) subcutaneous;
(ii) intramuscular;
(iii) intraperitoneal;
(iv) gavage;
(v) intravenous, using superficial blood vessels.
11 The induction of tumours, or spontaneous tumours, that cause no detectable clinical adverse effects including, in particular, small, subcutaneous, non-invasive nodules.
12 The breeding of a genetically altered animal, which is expected to result in a phenotype with mild effects.
13 The feeding of a modified diet that does not meet all of the animal’s nutritional needs and is expected to cause mild clinical abnormality within the time-scale of the procedure.
14 Restraint in metabolic cages for less than 24 hours.
15 A study involving—
(a) short-term deprivation of a social partner, or
(b) short-term solitary caging of an adult rat of a sociable strain or an adult mouse of a sociable strain.
16 Experimental models which expose an animal to noxious stimuli which—
(a) are associated with mild pain, suffering or distress, and
(b) the animal can successfully avoid.
17 A repetition or combination of any of the following procedures, as a result of which the animal is likely to experience short-term mild pain, suffering or distress or which does not cause significant impairment of the animal’s well-being or general condition—
(a) the assessment of body composition by non-invasive measures with minimal restraint;
(b) a monitoring electrocardiogram with non-invasive techniques with minimal or no restraint of a habituated animal;
(c) the application of external telemetry devices that is expected to cause no impairment to a socially adapted animal and does not interfere with normal activity and behaviour;
(d) the breeding of a genetically altered animal which is expected to have no clinically detectable adverse phenotype;
(e) the addition of inert markers in the diet to follow passage of digesta;
(f) the withdrawal of food for less than 24 hours in an adult rat;
(g) open field behavioural testing of a mouse.
Part 3
Moderate procedures
18 The repeated application of test substances which produce moderate clinical effects.
19 The withdrawal of blood samples from a conscious animal where—
(a) the blood withdrawn within an appropriate period for the animal exceeds 10% of the circulating volume of blood in the animal at the start of the period, and
(b) the volume of blood withdrawn is not replaced within that period.
20 An acute dose-range finding study, or chronic toxicity or carcinogenicity test, with non-lethal end-points.
21 Surgery under general anaesthesia and appropriate analgesia, associated with post surgical pain, suffering or impairment of general condition including, in particular—
(a) thoracotomy, craniotomy, laparotomy, orchidectomy, lymphadenectomy or thyroidectomy;
(b) orthopaedic surgery with effective stabilisation and wound management;
(c) organ transplantation with effective management of rejection;
(d) surgical implantation of catheters or biomedical devices such as telemetry transmitters or minipumps.
22 Models of induction of tumours, or spontaneous tumours, that are expected to cause moderate pain or distress or moderate interference with normal behaviour.
23 Irradiation or chemotherapy with—
(a) a sublethal dose, or
(b) an otherwise lethal dose with reconstitution of the immune system,
where any adverse effects are expected to be mild or moderate and to last for less than five days.
24 The breeding of a genetically altered animal which is expected to result in a phenotype with moderate effects, such as impaired organ dysfunction, or an underdeveloped physiological function.
25 The creation of a genetically altered animal through a surgical procedure.
26 The use of metabolic cages involving moderate restriction of movement over a period of up to five days.
27 A study with a modified diet that does not meet all of the animal’s nutritional needs and is expected to cause moderate clinical abnormality within the time-scale of the study.
28 The withdrawal of food for 48 hours in an adult rat.
29 Evoking escape and avoidance reactions where the animal is—
(a) unable to escape or avoid the stimulus, and
(b) expected to suffer moderate distress.
Part 4
Severe procedures
30 Toxicity testing, including in particular single dose acute toxicity testing, where—
(a) death is the end-point, or
(b) fatality is to be expected and a severe pathophysiological state is induced.
31 The testing of a device where failure may cause severe pain, distress or death of the animal including, in particular, cardiac assist devices.
32 Vaccine potency testing that is—
(a) characterised by—
(i) persistent impairment of the animal’s condition, or
(ii) progressive disease leading to death, and
(b) associated with long-lasting moderate pain, suffering or distress.
33 Irradiation or chemotherapy with a lethal dose—
(a) without reconstitution of the immune system, or
(b) with reconstitution of the immune system with production of graft versus host disease.
34 The induction of tumours, or spontaneous tumours, that are expected to progress to cause lethal disease associated with long-lasting moderate pain, suffering or distress including, in particular—
(a) tumours causing cachexia;
(b) invasive bone tumours;
(c) tumours resulting in metastatic spread;
(d) tumours that are allowed to ulcerate.
35 Surgical and other interventions in an animal under general anaesthesia which are expected to result in severe or persistent moderate postoperative pain, suffering or distress or severe and persistent impairment of the animal’s general condition.
36 Production of unstable fractures, or thoracotomy without adequate analgesia.
37 A procedure expected to result in multiple organ failure.
38 Organ transplantation where organ rejection is likely to lead to severe distress or impairment of the general condition of the animal including, in particular, xenotransplantation.
39 Breeding an animal with a genetic disorder that is expected to experience severe and persistent impairment of general condition including, in particular—
(a) Huntington’s disease;
(b) muscular dystrophy;
(c) chronic relapsing neuritis models.
40 The use of metabolic cages involving severe restriction of movement over a prolonged period.
41 Inescapable electric shock including, in particular, where it produces learned helplessness.
42 The complete isolation for a prolonged period of a social species, whether occurring once or on more than one occasion, including, in particular, a dog or non-human primate.
43 Immobilisation stress expected to result in gastric ulcers or cardiac failure in a rat.
44 Forced swim or exercise tests with exhaustion as the end-point.”.

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Source: https://www.legislation.gov.uk/ukdsi/2026/9780348281750/schedule (the official version)
Page: https://openlegislation.uk/draft-animals-scientific-procedures-act-1986-amendment-regulations-2026/schedule
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.