AAALAC International publishes “Guidance Statements” that are used as supplemental requirements or recommendations in dealing with certain issues.
On this page:
A. AAALAC International’s Assessment Process
B. Animals Included in the AAALAC International Accredited Unit
C. Institutional Responsibilities
D. Animal Environment, Housing, and Management
Mouse Cage Sanitation Frequency (May 2025)
F. Occupational Health and Safety
Temperature & Relative Humidity Control (September 2025)
AAALAC International promotes humane treatment of animals in science through voluntary accreditation and assessment programs. Its evaluations are based on widely accepted standards—principally, the Guide for the Care and Use of Laboratory Animals (Guide), alongside other recognized references such as the Guide for the Care and Use of Agricultural Animal in Research and Teaching (Ag Guide) and the European Convention ETS 123 (these three documents are the Primary Standards), AAALAC Position and Guidance Statements, as well as applicable legislation.
However, AAALAC International recognizes that rigid adherence to prescriptive guidelines may not always be the most effective or scientifically appropriate approach. Sometimes, thanks to the advent of new scientific information and new technology, there are situations where new methods or procedures not described in the Guide or other AAALAC standards may be available and result in equal or greater operational efficiency and welfare for the animals involved. In most cases, these exceptions involve a specific project or are limited in scope within an animal care and use program. Occasionally, exceptions are wider in scope and may involve the entire animal care and use program or even apply globally in the case of organizations with facilities in multiple countries; these are often referred to as program wide and global exceptions, respectively. As such, both types of exceptions to the Guide or other standards can be acceptable when justified and well-supported.
1. Performance-Based Approach
AAALAC endorses the performance-based approach to animal care and use. More information can be found in the Application of Performance Standards.
2. Flexibility Across Geographies and Models
AAALAC accredits animal care and use programs worldwide, spanning diverse regulatory, cultural, and scientific environments. As such:
3. Institutional Oversight and Documentation
Acceptable exceptions are not arbitrary. To be considered valid by AAALAC:
The concept of Performance Standards is explicitly highlighted in the Guide for the Care and Use of Laboratory Animals (Guide), Eighth Edition (National Research Council 2011). According to the Guide, the concept and application of Performance Standards is essential for the development of a comprehensive animal care and use program.
Regulations often include specific requirements on animal care and use program areas. When these requirements are rigid and measurable, they are called Engineering Standards. Typical examples of Engineering Standards are minimum animal primary enclosure sizes; ranges for environmental temperature, relative humidity, light intensity levels, and air exchange rates of animal rooms; lists of accepted or regulated procedures; minimum sanitation frequency of animal cages and accessories; and minimum temperature requirements for the rack washer rinse water. Engineering Standards do not provide for interpretation or any modification of the expected specific limits, parameters, or methods to achieve a particular outcome. Additionally, Engineering Standards may not exist for all species in the program.
Alternatively, Performance Standards define the outcome of activities or procedures in detail and provide criteria for assessing whether the outcome is achieved. These criteria may be based on simple measurable acceptable data (e.g., microbiological growth data after sanitation practices), or on more general interpretation of the outcome of a process (e.g., analysis of the questions raised on the oversight and ethical review processes).
AAALAC endorses the performance-based approach to animal care and use. This approach emphasizes outcomes—animal well-being, scientific validity, and regulatory compliance—over strict adherence to procedures. Institutions may deviate from Primary or other AAALAC standards or recommendations when:
This allows institutions to adopt innovative or tailored practices that suit their specific research, species, or facility conditions.
AAALAC International recognizes that the legal framework for the use of wild-caught animals in science and education can vary with local, state, national, or international regulations. In countries where regulations or guidelines may not exist regarding acquisition and use of wild-caught animals, AAALAC International recommends that institutions consider appropriate AAALAC International Reference Resources (https://www.aaalac.org/resources/reference-resources/ under "Species Specific") as baseline references. In all cases where the utilization of wild-caught animals is part of the accredited program, any applicable local and international regulations serve as the minimum standard, with guidance from the primary standards and Reference Resources utilized by AAALAC International supplementing these standards.
In situations where the need for non-purpose-bred animals is proposed and the justification for such use is not obvious from the study focus (e.g., research involving wild species), AAALAC International expects that the Institutional Animal Care and Use Committee or Oversight Board (IACUC/OB) will require a thorough and robust justification for the use of non-purpose-bred animals for any breeding or research purposes. Additionally, the IACUC/OB must ensure species-appropriate management of these animals.
The collective professional judgment of the IACUC/OB, principal investigator (PI), and Attending Veterinarian must ensure that all applicable legal and regulatory requirements are met for the capture, acquisition, and use of wild-caught animals. The institution should have a process to maintain and ensure appropriate management of any required regulatory documents and permits for the use of wild-caught animals. The Council on Accreditation may request documentation (e.g., applicable permits, acquisition records) to verify the legal acquisition of animals.
Scientific rigor and experimental reproducibility directly impact the welfare and number of animals used in research, testing and teaching. It is AAALAC International’s view that programs should consider scientific rigor and experimental reproducibility when evaluating animal research activities. The evaluation may be based on an initial review by a grants review panel, and/or may be assigned to the Institutional Animal Care and Use Committee or Oversight Board (IACUC/OB) internal protocol review process. In either scenario, the IACUC/OB review should confirm that the protocol contains pertinent study design elements and ensure adherence to the principles of the 3Rs (replacement, reduction, and refinement). That review should include aspects such as the adequacy of the rationale for the use of animals, the purpose and design of the research-- including randomization, blinding, and controls-- the justification of species, and the proposed animal numbers (via statistical power analyses, if appropriate). Moreover, it should also include consideration of the availability of alternatives to the use of animals, less invasive procedures, and use of less sentient species, as well as the ethical use of animals under appropriate experimental conditions and housing environments. Use of an experimental planning checklist (e.g., the PREPARE Guidelines) into animal protocols for submission and approval may help assure consideration of these elements. To increase awareness of and competency when evaluating rigor and reproducibility, the IACUC/OB should confirm that the program provides education/training as well as direction/recommendations related to scientific rigor and experimental reproducibility to researchers and their staff as well as the IACUC/OB members. Appropriate reporting of experimental design methods in peer-reviewed journals is another important aspect of scientific rigor and experimental reproducibility (e.g., using the ARRIVE guidelines). Guidance on various aspects of scientific rigor and experimental reproducibility may be found at:
ACD Working Group on Enhancing Rigor, Transparency, and Translatability in Animal Research. https://acd.od.nih.gov/documents/presentations/06112021_RR-AR%20Report.pdf
ARRIVE 2.0 Guidelines – a checklist for reporting in vivo experiments in enough detail to add to the scientific knowledge base; endorsed by over 1,000 journals worldwide and available in multiple languages. https://arriveguidelines.org/
Experimental Design Assistant – a free online tool to help design robust animal experiments more likely to yield reliable and reproducible results; recommended by major funders worldwide. https://eda.nc3rs.org.uk/
PREPARE Guidelines – guidelines for planning research and experimental procedures on animals. https://norecopa.no/prepare
Additional Guidance Documents (not to be confused with AAALAC International Reference Resources):
Leung, V., Rousseau-Blass, F., Beauchamp, G., & Pang, D. S. J. (2018). Arrive has not arrived: Support for the arrive (animal research: Reporting of in vivo experiments) guidelines does not improve the reporting quality of papers in animal welfare, analgesia or anesthesia. PLoS ONE, 13(5). https://doi.org/10.1371/journal.pone.0197882
Liu, Y., Zhao, X., Mai, Y., Li, X., Wang, J., Chen, L., Mu, J., Jin, G., Gou, H., Sun, W., & Feng, Y. (2016). Adherence to ARRIVE guidelines in Chinese journal reports on neoplasms in animals. PLoS ONE, 11(5). https://doi.org/10.1371/journal.pone.0154657
Macleod, M. (2019). Did a change in Nature journals’ editorial policy for life sciences research improve reporting? BMJ Open Science, 3(1). https://doi.org/10.1136/bmjos-2017-000035
Nunamaker, E. A., & Reynolds, P. S. (2022). ‘Invisible actors’—How poor methodology reporting compromises mouse models of oncology: A cross-sectional survey. PLoS ONE, 17(10 October). https://doi.org/10.1371/journal.pone.0274738
Reynolds, P. S., & Garvan, C. W. (2021). Preclinical Research Reporting in Shock: Room for Improvement. In Shock (Vol. 55, Issue 5, pp. 573–580). Lippincott Williams and Wilkins. https://doi.org/10.1097/SHK.0000000000001544
Zhao, B., Jiang, Y., Zhang, T., Shang, Z., Zhang, W., Hu, K., Chen, F., Mei, F., Gao, Q., Zhao, L., Kwong, J. S. W., & Ma, B. (2020). Quality of interventional animal experiments in Chinese journals: compliance with ARRIVE guidelines. BMC Veterinary Research, 16(1). https://doi.org/10.1186/s12917-020-02664-1
AAALAC International expects the Institutional Animal Care and Use Committee or Oversight Body (IACUC/OB) to regularly review the animal care and use program and inspect animal facilities. This includes centralized and satellite (not centrally managed or maintained) housing, support areas, and labs where animal procedures are done. Regular reviews and inspections are important for overall monitoring and oversight. The Guide recommends these reviews and inspections happen at least once a year, but other regulations may require increased frequencies. AAALAC International encourages the IACUC/OB to carefully consider how often they should evaluate to ensure quality animal care and science. In some cases, more frequent self-assessments may be wise.
AAALAC International expects these reviews and inspections should be frequent and thorough enough to identify and fix any issues in a timely manner. The IACUC/OB should show evidence of being actively involved in evaluating the program and facilities and ensuring corrective actions are timely. The findings from these reviews and inspections should be promptly communicated to the Institutional Official to support the institution's research, testing, and teaching goals.
The frequency of reviews should match the complexity of the program to ensure effective oversight. AAALAC’s site visitors may discuss the frequency based on performance-based outcomes. For example, if many issues are found across several program areas, this may indicate poor oversight by the IACUC/OB. This performance-based approach can also be used to adjust the frequency of reviews for specific areas or facilities based on past concerns.
AAALAC International recognizes that the legal framework for the use of wild-caught animals in science and education can vary with local, state, national, or international regulations. In countries where regulations or guidelines may not exist regarding acquisition and use of wild-caught animals, AAALAC International recommends that institutions consider appropriate AAALAC International Reference Resources (https://www.aaalac.org/resources/reference-resources/ under "species-specific") as baseline references. In all cases where the utilization of wild-caught animals is part of the accredited program, any applicable local and international regulations serve as the minimum standard, with guidance from the primary standards and Reference Resources utilized by AAALAC International supplementing these standards.
In situations where the need for non-purpose-bred animals is proposed and the justification for such use is not obvious from the study focus (e.g., research involving wild species), AAALAC International expects that the Institutional Animal Care and Use Committee or Oversight Board (IACUC/OB) will require a thorough and robust justification for the use of non-purpose-bred animals for any breeding or research purposes. Additionally, the IACUC/OB must ensure species-appropriate management of these animals.
The collective professional judgment of the IACUC/OB, principal investigator (PI), and Attending Veterinarian must ensure that all applicable legal and regulatory requirements are met for the capture, acquisition, and use of wild-caught animals. The institution should have a process to maintain and ensure appropriate management of any required regulatory documents and permits for the use of wild-caught animals. The Council on Accreditation may request documentation (e.g., applicable permits, acquisition records) to verify the legal acquisition of animals.
Behavioral Management is a comprehensive approach aimed at enhancing the welfare and health of research animals and consequently, research reproducibility. By focusing on species-specific behavior as a key indicator, a Behavioral Management program improves various aspects of animals’ lives, including but not limited to housing, husbandry, and handling techniques.
A comprehensive approach to Behavioral Management should be an essential element of the animal care and use program. Considerations for cage, pen or enclosure space and how it is furnished, choice of substrate/bedding, social housing (see relevant Position Statement), animal handling and restraint, opportunities for choice and control of aspects of their home enclosure, appropriate preparation of animals for research through habituation and training, opportunities for exercise, and provision of food and other resources to provide stimulation and alleviate boredom should be included.
The institutional Animal Care and Use Committee or Oversight Board (IACUC/OB) should identify appropriate performance criteria, as well as a process for assessment, and ensure that the adequacy, safety, comfort and configuration of the animal environment is regularly reviewed to meet animal welfare and research quality needs. Animals should be adequately acclimated to their environment, as well as habituated to handling before experimentation begins to reduce stress as well as experimental variability. Non-aversive animal handling and positive reinforcement training methods should be used whenever possible to minimize stress and it should be performed by adequately trained personnel.
When developing a performance-based approach to Behavioral Management, careful consideration should be given to addressing the specific needs of each species, taking into account factors such as, age, sex, animal size, group sizes and social structure, duration of study and behavioral needs according to current scientific understanding.
Behavioral Management should be applied to all animals including commonly used species such as mice, other rodents, and fish. The following species exhibit unique Behavioral Management and housing needs in addition to what is already described in the Primary Standards and Position Statements.
Dogs are generally social, athletic animals with a strong affinity for people. In managing the behavior of laboratory dogs, it is essential to address their social and physical needs to enhance welfare:
Nonhuman primates are non-domesticated species with significant cognitive capacity and require thoughtful housing and Behavioral Management programs to reduce the likelihood of injuries, boredom and frustration from developing in captive research settings. Key Behavioral Management needs for primates in research include appropriate housing environments, opportunities for social housing with familiar animals, habituation and desensitization to facility personnel, as well as research equipment and procedures, stimulating resources that are rotated on regular intervals to reduce boredom, and training to increase predictability and reduce stress during various procedures.
Although inherently social creatures, rabbits are a highly territorial species and social incompatibility issues often arise when they are not provided with sufficient space in their home enclosure. Intact adult males may not aways be suitable for social housing because of behavioral aggression, but juvenile rabbits, castrated male rabbits, and intact adult females may often be socially housed (generally in same sex groups in research settings). Does with litters should be housed separately from other rabbits, but kits can be mixed between litters at weaning. It is essential to provide hiding places and escape routes when introducing adult females to minimize agonistic encounters. As relationships between animals can evolve due to changes in physiological status, age, and experimental manipulation, ongoing observation of rabbit interactions is needed to detect and promptly address significant signs of social incompatibility.
Other factors that may improve the Behavioral Management of rabbits include:
Rats are highly intelligent and social animals that respond well to positive human interactions. Consideration for housing and optimal Behavioral Management for rats in research settings has not generally kept pace with other species. As for other species, rats benefit from opportunities to perform a full range of postural adjustments and movements, including climbing, stretching vertically, hopping, and running and facilitation of such behaviors should be considered. Except for stud males kept long term for breeding, it is rare for rats of either sex to require separation due to intolerable agonistic encounters. As for other species, rats require sufficient space and enclosure furnishings (e.g., tunnels or huts) to be able to move out of sight and avoid agonistic encounters. Other factors that may improve Behavioral Management of rats include:
Most AAALAC-accredited facilities will already have many aspects of a Behavior Management program in place. These should be incorporated into a coherent program, expanded where needed, and tailored to each species housed within the facility. A key means of improving current programs is to employ an ‘outcomes-focused’ approach, that is, one that asks what behaviors are normal for a given species and should be promoted. Addressing some needs may require structural modifications of housing enclosures; however, other needs can be met with simple materials or procedural changes. This will remain an evolving area within the field and one that accredited units should continue to monitor to ensure they are promoting good animal welfare and quality science.
Maintenance of monogamous pair breeding mice (one adult male and one adult female) is simple and allows tracking of their litters and minimizes overcrowding. In general, outbred mice that produce larger litters are best propagated by a pair breeding strategy. However, continuous mouse breeding groups (such as trio breeding, one adult male and two adult female mice, or harem breeding, one male and three or four adult female mice) is commonly proposed to increase breeding efficiency, especially for some strains that are difficult to propagate.
Individuals responsible for the maintenance of these colonies who propose the group breeding scheme must accept full responsibility of the health and welfare of the animals and establish additional animal husbandry criteria to ensure adequacy of cage space for mothers and pups. The increased husbandry practices should include but not limit to ensuring adequate animal observation and frequency, applying established criteria for separation of pregnant females and multiple litters, the suitable cage change frequency, the prompt weaning of mature pups as well as the prompt separation of animals if the number of animals becomes greater than the established criteria.
When considering cage space/animal density policies, it´s expected that the Institutional Animal Care and Use Committee or comparable Oversight Body (IACUC/OB) always considers national or regional regulations, policies and guidelines animal behavioral needs, and critically evaluates objective measures of outcome-based performance standards. The proposed cage type should allow all animals to make normal movements and postural adjustments and rest away from soiled areas, provide free access to food and water, and provide sufficient space for mothers with litters to allow the pups to develop to weaning age without detrimental effects to the mothers or the litters. This evaluation should include consideration of strains that have potential large litter sizes, number of adults, the age of female mice, the need for cross-fostering, the growth rate of pups and the average litter size or whether one or more litters are present or possible number of different litters of pups at potential age ranges, the calculation of anticipated number of animals to be produced and to be used or the plan needed for surplus animals, as well as the successful outcomes that support animal well-being.
While the Guide for the Care and Use of Laboratory Animals (Guide), NRC 2011 recommends solid bottom cages be sanitized at least once a week, it goes on to say that some types of cages might require less-frequent sanitation, which include individually ventilated cage (IVC) units. The Guide stresses the use of performance standards when making these determinations. As an example, scientific studies have looked at environmental conditions (1) and cage changing frequency (2) for IVC systems and determined that under normal circumstances, changing cages in these types of units once every two weeks provided for an acceptable environment for the mice. However, there are other factors to take into consideration. While this frequency of cage changing may be acceptable for many mice, it may not be acceptable for others (e.g., diabetic mice that exhibit increased urine output). The Institutional Animal Care and Use Committee or comparable oversight body (IACUC/OB) should review current cage changing practices for IVC units based on current literature and other factors (phenotype of the mice, type of bedding, housing density, etc.). For an IVC cage change interval longer than 2 weeks, verification of microenvironmental conditions may include measurement of pollutants such as ammonia and CO2, microbiologic load, observation of the animals' behavior and appearance, and the condition of bedding and cage surfaces. Also, as with any performance standard, there should be a system in place to monitor the outcome and report back to the IACUC/OB.
Because anesthesia is a critical component of the veterinary care program, and the use of anesthetic gases may pose a risk to personnel, anesthetic machines and vaporizers should be evaluated for safe and effective operation. This should follow an established schedule, consistent with the intensity of use and manufacturers’ recommendations. Properly functioning gas anesthesia machines and vaporizers are key to the delivery of accurate doses of anesthetic agent to the animal, and to the safety of personnel, avoiding the exposure to waste anesthetic gases.
The precision vaporizer should be maintained according to the recommendations of the manufacturer and may include on-site calibration and/or having the precision vaporizer returned to the manufacturer for more extensive work. Factors that may affect the schedule for service include the type of anesthetic agent used, the frequency of use of the machine, as well as the type of vaporizer used.
The anesthesia machine (what the vaporizer is attached to) can vary in complexity. There are many factors to consider (e.g., frequency of use, age of machine, environmental conditions, etc.) when developing a program for anesthesia machine maintenance and upkeep, and all components need to work properly as an integrated unit.
Several aspects may be considered for the calibration and maintenance program:
More detailed guidance on checking anesthetic equipment can be found at: https://anaesthetists.org/Home/Resources-publications/Guidelines/Checking-Anaesthetic-Equipment
AAALAC International considers allergy prevention to be an important topic and a key component of the occupational health and safety program. The use of engineering controls (appropriate facility design, operation, and use of safety equipment) is preferred as the primary means to minimize personnel allergen exposure. Administrative controls (appropriate processes and procedures) are the secondary means to reduce allergen exposure. Personal Protective Equipment (PPE) should be used as an adjunct to engineering and administrative controls, rather than the initial or single means of protection. The activities most associated with allergen exposure are handling animals, cage changing, dumping soiled bedding, and other routes of exposure to animal excretions (such as laundry). Appropriate engineering controls may include: proper animal facility design and function with separation of functional spaces; a well-designed heating, ventilation and air conditioning (HVAC) system with appropriate airflow patterns and air pressure differentials; consideration of cage systems and designs which minimize personnel exposure; and the use of containment equipment such as cage changing stations, bedding dump stations, and other exhausted or downdraft work benches. AAALAC International site visitors evaluate occupational health and safety programs and the methods used to prevent or minimize research animal allergen exposure through review of the procedure of risk assessment by qualified occupational health and safety personnel, periodic personnel health evaluations, engineering controls, administrative controls, the appropriate selection and use of PPE, and ongoing personnel education and training.
As part of the occupational health and safety program, consideration should be given to personnel exposure to harmful airborne particulate materials or vapors including dusts, fogs, fumes, mists, gases, smokes, sprays, and animal allergens. The primary protection should focus on preventing or minimizing atmospheric contamination with engineering control and administrative control measures. If, following appropriate risk assessment, it is decided that personal respiratory protective equipment is needed in addition to available engineering/administrative control measures, the ancillary guidance, as described below, should be considered to assure personal protection when respirators are used.
When personal protective equipment are necessary to protect individuals from contaminant exposure, an institutional program (Respiratory Protection Program or Personal Protective Equipment Program) is required. The Program is a cohesive collection of written worksite-specific procedures and policies that, taken together, address all relevant respiratory protection elements, including guidance for personal protective equipment selection (including appropriate protection factors); evaluation by an occupational health professional of the suitability of the individual to be medically able to wear the respirator and health hazards associated with the use of respiratory protection devices; qualitative and/or quantitative fit testing*; and respirator use training to include inspection, maintenance and care, quality, quantity and flow of breathing air, and routine and emergency use procedures.
When selecting personal protective equipment, it is important to consider that respiratory protection devices are specific to (or appropriate for) the contaminant type. For example, an N95 or FFP1-3 filtering face piece is often used for protection for respirable dust, smoke, and aqueous fog (aerosols), whereas chemical or gas exposures are better mitigated with a Chemical Cartridge/Gas Mask, Powered Air-Purifying Respirator (PAPR), or Self-Contained Breathing Apparatus (SCBA). Note that for air-purifying respirators, knowing the hazard and the amount of hazard in the air is important for selecting the proper filters/cartridges. Additionally, most dust masks or medical (surgical) facemasks do not seal tightly to the face, thus allowing airborne hazards, including animal allergens, to enter the breathing zone; and are not approved as respirators.
Although the Guide indicates that rooms with MR scanners or in which cryogen gases are stored must be equipped with oxygen sensors and a method for increasing room ventilation to exhaust inert gases during cryogen filling, AAALAC International recognizes that institutions may apply a variety of alternative methods to maintain personnel safety in areas where cryogen gases are used. AAALAC International expects that all institutions, through their occupational health and safety program, should conduct a critical risk assessment of hazards associated with the management of MR scanners and cryogen gases and implement appropriate safety measures to protect personnel. This should include periodic reassessment of safety equipment and procedures. Personnel working in these areas should be trained to recognize the hazards associated with MR scanners and cryogen gas storage, and in the relevant safety features and procedures.
The importance of temperature and relative humidity (RH) relates to thermoregulation, important for animals or species with limited capacity to regulate body temperature (e.g., neonates, amphibians); respiratory health, because extremes in temperature or RH may exacerbate respiratory conditions or support growth of pathogens or allergens; or other specific pathological problems (e.g., ring tail due to prolonged low RH).
However, the control of temperature and RH is particularly difficult in certain areas due to extreme climate and limitations of heating, ventilation and air conditioning systems. Additionally, animal husbandry activities may provoke temporary fluctuations (e.g., residual water in large species enclosures).
Rather than prescribing rigid numerical limits, AAALAC International embraces a performance-based approach that allows institutions to justify and demonstrate how their environmental parameters meet the needs of the species housed and support the goals of the animal care and use program. In this context, AAALAC encourages institutions to:
If no issues are identified by the institution or the AAALAC site visit team that may compromise the health and well-being of the animals or jeopardize the integrity of animal studies, then it is not likely that the Council on Accreditation considers this variation a problem. If, however, animal welfare or study issues are reported that can be linked to variation in temperature or relative humidity, then AAALAC expects the institution to address the lack of control of temperature or RH to ensure animal welfare and reliable data..