Animal Care and Use

Standards for Housing Rats and Mice Greater than 24 Hours Outside DCM Facilities

Created prior to 01/2012
Revised 09/2016


Rats and mice at Washington University are to be housed within DCM’s centralized animal housing facilities. Proposed housing of animals outside DCM facilities for greater than 24 hours either in laboratories assigned to a PI or PI/Departmental space that is/will be redefined for temporary housing of animals (aka, ‘a satellite facility’) will be reviewed by the IACUC on a case-by-case basis and may be allowed only when adequately justified on a scientific basis. Approval is protocol specific and dependent on following the Standards of this policy.


Washington University in St. Louis is committed to a uniform standard of excellence in all aspects of its animal care and use program. The entire program is based on the recommendation of the Guide for the Care and Use of Laboratory Animals (Guide).1 The Guide provides detailed standards of temperature, humidity, ventilation, lighting, sanitation, daily care, and numerous other criteria that are to be met in the housing of live vertebrate animals. These standards are to be met whenever and wherever animals are housed.

The Washington University Division of Comparative Medicine (DCM) operates centralized animal housing facilities that meet the criteria listed in the Guide. Housing animals within DCM facilities is the most practical means of attaining the standards set forth in the Guide. Some experimental uses of animals may involve equipment or procedures that necessitate animals be housed (i.e., maintained for >24 hours) in non-DCM space. It is the Principal Investigator’s (PI’s) responsibility to assure that animal care and lab housing is conducted in accordance with the approved protocol and that all lab personnel abide by IACUC policies and guidelines and the Guide. Lab housing approval is subject to revocation in the case of noncompliance with IACUC Polices, DCM policies and/or the Guide. The following Standards address the requirements for housing of animals outside DCM facilities.


  1. Protocol Requirements: Proposed lab housing must be described in the relevant IACUC protocol in Section IX.a.: “Housing Outside Central Animal Holding Facility.” Information provided by the PI in this section must include:
    • Strong scientific justification for lab housing, including a description of the specific procedure(s) and/or equipment that merit consideration for lab housing. Personnel convenience is not an acceptable rationale for lab housing.
    • Maximum duration for housing any one animal.
    • Average number of animals estimated to be housed at any one time.
    • Care and monitoring procedures for animals housed in the lab.
    • Point of contact (POC) staff with delegated authority from the PI to be responsible for the animals housed in the lab and the training of other staff or students who may use the animals.
  2. IACUC Review of Proposed Lab Housing in a Protocol:
    • The IACUC reviews proposals for lab housing on a case-by-case basis. The rationale must convey that lab housing relates to the use of equipment, procedures, or frequency of animal contact that are integral to the associated animal study, and why they cannot be done in DCM facilities.
    • Under some circumstances, the Attending Veterinarian (AV)/DCM veterinary staff may approve lab housing on a one-time basis or pending IACUC approval of such housing. The AV/DCM must inform the IACUC office at the time of approval.
    • Approvals for lab housing are only valid for the specific protocol, species, number of animals and specific projects (or group of animals within a protocol) for which IACUC approval has been obtained. It is not to be considered a “blanket approval” for the lab.
    • If the proposed lab housing site is new to the IACUC, there may be a review of the proposed site performed in conjunction with the associated protocol review.
    • Lab housing may not commence unless and until approved is granted by the IACUC. If approval is not granted by the IACUC, lab housing is not allowed.
    • If approved for lab housing, the entry point to the site must be identified by posting the PI name, current protocol number, and emergency contact information for the PI, Point of Contact, and any designees.
    • Animals must be held under secure conditions such that they cannot escape from their enclosures or be removed from the lab by unauthorized individuals.
    • Once approved for lab housing, the associated site is subject to unannounced semi-annual inspection by the IACUC’s QA/QI staff. Inspection may also be required during unannounced OLAW or AAALAC site-visits.
    • Noncompliance with the lab housing standards described in this policy may result in revocation of lab housing privileges and possible protocol suspension.
  3. The Laboratory Point of Contact (POC):
    • This person may be either the PI or another person with delegated responsibility.
    • The POC may operate by directing and overseeing others in the lab that are performing hands-on care or may perform laboratory-based care as a primary function.
    • The POC is required to be familiar with and to follow the provisions of this policy, the IACUC protocol, and any other institutional standards that apply.
    • The POC is also responsible for:
      • Training new staff to ensure they have a clear understanding of this policy before they are allowed to provide any animal care (checking animals, feeding, cleaning, etc.) or initialing any animal care forms.
      • Review of the Lab Housing Logs for completeness and accuracy.
  4. Daily Checklist (including weekends and Holidays):
    • Most of the critical elements of a basic program of laboratory-based care are included in the Lab Housing Log. This log provides a means for recording basic required elements of animal maintenance (i.e., temperature and humidity in the animal housing location as well as a confirmation that all animals were visually inspected seven days a week, including weekends and holidays.) It may also incorporate other actions performed in support of the animals in the location.
    • Qualified personnel must provide care for animals every day—including weekends and holidays— and initial or sign the Lab Housing Log at the time of checking on/caring for the animals each day.
    • For shared spaces, each PI or their designee (i.e., POC or other staff) is responsible for providing the animal care and completing the required documentation for the animals under their protocol only.
    • Each approved protocol for lab housing must use a separate Lab Housing Log.
    • 24-hour/7-day emergency contact and backup information must be posted outside the animal housing area.
    • The Attending Veterinarian (or their designee) must be contacted for concerns about animal health.
  5. General Housekeeping Provisions for Lab Housing:
    • The housing area must be maintained in a clean and orderly condition.
    • The placement of standard rodent housing cages must permit easy visualization of the animals contained within unless otherwise dictated by the requirements of the experimental protocol.
    • The housing area must be arranged to facilitate sanitation and pest control.
      • Remove laboratory apparatus, equipment, furniture, books and supplies that are not needed for ongoing experimental or husbandry needs. Fabric-covered furniture must be moved out of the area as fabric-covered surfaces are not easily sanitizable.
      • Where practical, movable racks or carts must be used to hold the animal cages. There must be enough room between the bottom of the rack/cart and the floor to clean underneath them, especially if the rack/cart is not easy to move.
      • Corrugated cardboard boxes must be moved away from the animal housing area,
      • The floors of the housing area should be swept daily and mopped once weekly.
    • Potentially harmful chemicals should not be stored near the animal cages. They can be stored in biosafety cabinets or fume hoods when animals are present in the lab.
    • Bench space used for animal manipulations must be wiped down with disinfectant solution after each use.
    • For shared spaces, each PI is responsible for sharing in the responsibility of maintaining an acceptable level of cleanliness in the lab. In the event the condition of the lab housing area is found to be unacceptable, the IACUC will be notified. This could lead to revocation of the lab housing privilege.
  6. Primary Enclosure (Cage):
    1. Cage and Sanitation:
      • The acquisition of clean caging and supplies must be coordinated through DCM. Any exceptions (i.e., special caging, use of wire bottom cages) must be described and approved in the SOP Exemptions section of the IACUC protocol.
      • Maximum animals allowed per standard shoebox cage:
        • Mice – up to 5 adult mice per cage
        • Rats – up to 3 adults per cage
      • Cages must allow for normal physiological and behavioral needs of the animals, including urination, defecation, maintenance of body temperature, normal movement and postural changes, and, where indicated, reproduction.
      • Cages must be identified with a current cage card per the IACUC policy on Animal Identification.
      • Special cage cards will be provided and must be used to aid in communication between researchers, DCM and QA/QI staff for documentation of post-procedure monitoring, hazard notification, or other special conditions.
      • All cages must have microisolator bonnets (plastic lids with filter inserts) to reduce potential allergens and transmission of rodent pathogens.
      • Cages must be changed at least once per week (or more if necessary). Individuals must wear a lab coat or gown, exam gloves, and mask when changing cages.
      • Cages containing animals must not be stacked directly on top of one another to allow for proper air flow.
      • Cages containing animals must not be placed on the floor.
      • Used cages must be promptly returned (by Friday of that work week) to the appropriate DCM animal facility to decrease odors and allergens and prevent attraction of vermin.
    2. Food:
      • Animals must be supplied with nutritionally adequate food at all times unless approved otherwise in the IACUC protocol or by a DCM veterinarian providing treatment to the animal.
      • To ensure opened food remains fresh and uncontaminated and does not attract vermin, it must be stored in a tightly sealed container.
      • If it is necessary to store unopened fed bags in the lab, they must be off the floor (e.g., on a pallet) and away from the wall.
      • The container must be labeled with the mill date (manufacture date, which is found on the feed bag) for the contained feed. Feed must be used before the expiration date, which is 180 days (6 months) beyond the mill date in most cases.
      • Follow directions provided with the feed or special diet for proper storage temperature; directions must be readily available in the lab.
      • In the absence of directions, comply with the recommendations in the Guide. Contact the DCM Vet Staff if there are questions.
    3. Water:
      • Animals must have access to potable, uncontaminated drinking water at all times unless approved by the IACUC in the animal protocol.
      • Watering devices must be checked daily to ensure proper functioning.
      • Water bottles must remain with the same animal(s) if they are refilled.
      • Water bottles must be replaced with clean (sanitized) water bottles at least once per week.
    4. Bedding:
      • Bedding must be obtained from DCM animal facilities unless other circumstances are described in the animal protocol and approved by the IACUC.
      • Bedding must be transported and stored off the floor to maintain quality and minimize contamination.
      • Bedding in conventional rodent caging and the cage itself must be changed at least once a week or more frequently if wet or dirty.
      • To prevent foot sores, the layer of bedding must be deep enough that the animal is not walking on the bottom of the cage.
    5. Environmental Enrichment:
      • Avoid single housing of social animals whenever possible and limit the amount of time social animals are singly housed. Prior to implementation of single housing, this practice must be reviewed and approved by the IACUC based on scientific justification provided by the PI.
      • Provide nesting material (mice), shelters (e.g. igloos), Nylabone® chew toys (rats) and other devices to allow for normal nesting and chewing behavior. See the IACUC Enrichment and Social Housing Policy for details. Check with DCM Vet Staff if there are questions regarding enrichment.
  7. Secondary Enclosure (Room or Cabinet):
    1. Environmental monitoring in the housing room or lab:
      • The room housing animals or other secondary enclosures (housing cabinet) must be maintained at humidity 30-70%, temperature 20-26°C (68-79°F) with ventilation sufficient to maintain appropriate temperature and humidity ranges and to control odor. Any exceptions must be approved in the IACUC protocol.
      • The secondary enclosure must have an environmental monitoring system (e.g., Sensaphone or equivalent) that is capable of notifying the PI &/or the POC(s) or other responsible staff members if room conditions exceed parameters noted above.
      • Air pressure should be negative to the hallway or rest of the lab to control odors.
    2. Lighting:
      • Lighting should be appropriate for the well-being of the rodents, good housekeeping practices, and adequate inspection of animals and safe working condition for personnel.
      • If a timer is employed, its performance should be checked periodically (e.g., daylight savings time change) to ensure proper operation. Keep a record of the timer verification assessments posted near the timer so it is accessible to inspectors.
      • If there will be natural light via windows, rather than control of diurnal cycle by a light timer, then a method of assuring that room lights are turned off after work hours should be described in the protocol. A light:dark cycle of 12 hours on:12 hours off should be maintained.
      • Cages should not be placed next to exterior windows unless temperature gradients and problems from direct sunlight are considered and addressed appropriately.
      • Any exceptions to the lighting requirements should be documented in the SOP exemptions section of the approved IACUC protocol.
  8. Sanitation:
    • Equipment used for animal research should be designed and constructed to allow efficient cleaning or sterilization as necessary for effective infection control measures.
    • Equipment that can be sanitized (or sterilized) in a glassware washer or DCM cage washer is automatically afforded the benefit of existing quality assurance measures (i.e., temperature-time monitoring, microbial monitoring).
    • As noted in the Guide, hand sanitation is less reliable than cage washing. For any caging and specialized equipment that must be sanitized by hand, laboratories must have written SOPs that describe the sanitation process, specify the chemical agents used, and indicate the contact times necessary for disinfection. This requires a onetime verification of adequate sanitation through DCM. Please contact the DCM Diagnostic Lab for more information.
    • Racks must be wiped clean at least once a week with a disinfectant.
    • Floors must be swept daily (Monday–Friday) and mopped at least once per week.
    • Documentation of routine sanitation that identifies the individual(s) responsible is required.
    • Animal carcasses must be bagged and moved to dedicated cold storage or a DCM animal freezer.
    • Contact the Environmental Safety Office (ESO) for procedures regarding hazardous waste disposal.
  9. Security and Access Control:
    • Only authorized, trained personnel who are listed on the approved IACUC protocol should have access to animals. The security of the animal holding site is particularly important after normal work hours.
    • The AV must have access to the housing area(s) 24 hours a day for inspection and care of the animals in case of an emergency involving the building.
  10. Recordkeeping:
    • A Lab Housing Log must be accurately maintained and kept in/near the housing site. Additions and subtractions of animals must be recorded according to DCM procedures.
    • Entries are to be made on the day(s) tasks are completed. Falsification of data entry is a serious matter that will be reviewed as a noncompliance issue by IACUC.
    • Completed Lab Housing Logs must be maintained on file for at least three years.


  1. The Guide for the Care and Use of Laboratory Animals: 8th Edition. (Guide). National Research Council. 2011
  2. Public Health Service Policy on Humane Care and Use of Laboratory Animals. Office of Laboratory Animal Welfare (OLAW)