Home Office Guidance Note
Water and Food Restriction for Scientific Purposes

Summary:
Where possible traditional food and water restriction paradigms should be replaced by reward
paradigms and only if this is found, or is known, to be inappropriate should restriction paradigms beconsidered.
As a general rule, when undertaken for a scientific purpose, all food restriction should be kept to theabsolute minimum required to achieve the scientific objective. Project Licence authority which clearlyjustifies the work and the benefits that should result will be required for:• all work which restricts food intake to a point where weight loss, or reduced weight gain, of morethan 15% of age and sex matched non-deprived animals might occur or• all work where animals are to be maintained below 85% of body weight for age and sex matched
controls fed ad libitum.
This guidance does not apply to simple dietary studies in farm animals, which will be covered
separately.
Water should be made available ad libitum at all times. Water withholding is not regulated when it isremoved as part of recognised husbandry practices. Regulation under the Animals (ScientificProcedures) Act 1986 (ASPA) is necessary when the programme of work to be applied requires water
withdrawal that may result in pain, suffering distress or lasting harm and is applied for a scientificpurpose.
For Guidance:
With respect to food restriction current Home Office guidance, as applied to Schedule 2 listed species,and ruminants, recommends that as long as no additional factor other than food deprivation is applied
exceeding the following food deprivation times for scientific purposes requires Project Licenceauthority:
16 hours Mice, young hamsters and rats under 100gms
24 hours Rabbits, rats, dogs, cats and non-human primates weighing over 100gms
See Note 1 Adult ruminants and other farm animals (including chickens and turkeys)
Note 1: The Home Office considers that any restriction of food and water for a scientific purpose which
would breach other welfare legislation (e.g. The Welfare of Farmed Animals (England [SI 1870] orNorthern Ireland [SI 270] Regulations) or current DEFRA Welfare Codes for that species will require1

regulation under ASPA.
Note 2: Food restriction should be avoided in guinea pigs, ferrets and shrews.
Note 3: The deprivation of food or water combined with one or more additional factor(s) (e.g. highprotein diet, concurrent disease) may require a reduction in these times if additional suffering isconsidered likely.
Note 4: Authority is also required if animals are exposed to repeated daily periods of deprivation
shorter than detailed in the table above.
Licensees using water restriction should keep the following records for each animal:• Daily water consumption, food consumption, body weight• Frequency of surgical intervention (if appropriate)• Frequency of infections/treatments (if appropriate)• Duration of study and future plans for the animal (if appropriate)• A record of all treatments given
Unless there is a veterinary contraindication or a justified scientific reason for not doing so, animals
should be returned to ad libitum water at least 24 hrs before a procedure that requires anaesthesia
and should remain on ad libitum water for at least 48 hrs after the conclusion of the procedure. Water
provision must also be increased when an animal:• is showing clinical signs of dehydration• is treated for disease• is exhibiting a weight loss
• is young and is failing to gain a reasonable weight increase during the time when it should begrowing• is considered, by a veterinary surgeon, to be compromised due to some other circumstance.

2