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Unit Four – Animal Husbandry and the Animal Facility

The appropriate care and use of animals requires an understanding of the importance of husbandry and the animal environment, not only for humane reasons, but also to control unwanted variation during experimentation.



The Guide for the Care and Use of Laboratory Animals was introduced in Unit Two, but two of its chapters are directly relevant to this discussion; read “Animal Environment, Housing and Management” and “Physical Plant.” The Guide is typically regarded only as a regulatory document, but it is very different from the AWARs. It was prepared by an expert panel, and relies heavily on published information.


Importance of husbandry and the animal environment – Control of unwanted variation

“Animal husbandry” is probably used most often in the context of agriculture – “a branch of agriculture concerned with the production and care of domestic animals,” according to Webster. In the laboratory animal business, the term often is used to encompass the wide array of activities associated with the maintenance of animals used in research, and the assigned readings provide an overview of those areas. In Chapter 2 of the Guide, husbandry is used in a perhaps more limited way, as only one component of “Animal Environment, Housing and Management,” but that distinction seems unimportant. The introduction to that chapter talks about the management of animal facilities, which is another way of describing laboratory animal husbandry:

“A good management program provides the environment, housing, and care that permit animals to grow, mature, reproduce, and maintain good health; provides for their well-being; and minimizes variation that can affect research results.”

Implicit in this statement is an ethical obligation to provide for the basic needs of animals in our charge. This is captured in U.S. Government Principle #VII, and is also one of the most basic refinements we can make in animal experimentation. While there may be scientifically justifiable potential for pain or distress in some experiments, there seems no justification for animals experiencing pain or distress when not on experiment. Furthermore, providing for an animal’s well-being is an acknowledgement that our obligations go beyond the minimum of avoiding pain or distress.

U.S. Government Principle VII. The living conditions of animals should be appropriate for their species and contribute to their health and comfort. Normally, the housing, feeding, and care of all animals used for biomedical purposes must be directed by a veterinarian or other scientist trained and experienced in the proper care, handling, and use of the species being maintained or studied. In any case, veterinary care shall be provided as indicated.


Control of unwanted variation is another component of good laboratory animal husbandry. There are an abundance of factors that may have an influence on the research animal. (An excellent discussion is Lipman, NS and SE Perkins. Factors that may influence animal research, pp. 1143-1184. In JG Fox et al. (eds.): Laboratory Animal Medicine, 2nd ed. Elsevier Science, 2002.) Some are perhaps obvious, and may be a direct threat to the health or well-being of an animal (e.g., severe alterations in room temperature). However, more often there is the potential for very subtle effects on the animal, effects that could complicate, or confound, the interpretation of experimental data. Much of what the animal facility manager does on a daily basis is oriented toward this key principle, and involves everything from using standardized diets to minimizing temperature fluctuations in the animal room.

The role of the laboratory animal veterinarian was discussed in Unit Three in the context of minimizing pain and distress. Another key function is relevant to this discussion, i.e., control of unwanted variation due to the presence of infectious disease. Like environmental variables, some infectious disease agents may have an obvious effect on the health of an animal. However, there are many agents that infect laboratory animals without causing obvious clinical signs, but have a serious confounding effect on the research. Mouse hepatitis virus is just one example of a rodent pathogen that can wreak havoc on a variety of immunological studies without causing obvious illness.

“A primary objective of laboratory animal science and medicine is to control variables in the research environment. Control of genetic variables is primarily a matter of biology, but control of other variables [microbial, chemical, physical] is dependent to a significant degree on the design and management of the research animal facility. Controlling environmental variables is critical because the reliability of research data is no better than the least reliable link in the chain of procedures used to derive the data. It is the role of laboratory animal specialists to assist the scientist with controlling animal-related variables in order to make the animal link in the chain as reliable as possible.” (Hessler, JR and SL Leary. Design and management of animal facilities, pp. 909-953. In JG Fox et al. (eds.): Laboratory Animal Medicine, 2nd ed. Elsevier Science, 2002.)


Legal requirements and standards

The Animal Welfare Act regulations (AWARs) were introduced in Unit Two. Part 3 of the regulations are referred to as the Standards, and consist of a number of Subparts, each of which covers a species or groups of species (e.g., Subpart A contains specifications for dogs and cats; Subpart B covers guinea pigs and hamsters; etc.). Within each subpart are detailed regulations grouped under facilities and operating standards, animal health and husbandry standards, and transportation standards.

Many of the AWA facility and husbandry regulations are written in general terms. For example:

“Housing facilities for dogs and cats must be designed and constructed so that they are structurally sound. They must be kept in good repair, and they must protect the animals from injury, contain the animals securely, and restrict other animals from entering.”

Other AWA regulations are often referred to as “engineering standards,” because they require very specific things, rather than referring to a more general “performance standard” that focuses on outcomes. Examples include specific temperature ranges in housing areas, minimum floor (cage) space and height for each animal, and frequency of cage sanitization.

The reading assignment for this Unit is from the Guide for the Care and Use of Laboratory Animals, which is the principal standards document referred to in the “Public Health Service Policy for the Humane Care and Use of Laboratory Animals,” and used by AAALAC in its accreditation program. Although the Guide contains some specific recommendations with respect to, e.g., temperatures and floor space, it is in general focused on performance standards (see text-block).

      “The Guide charges users of research animals with the responsibility of achieving specified outcomes but leaves it up to them how to accomplish these goals. This “performance” approach is desirable because many variables (such as the species and previous history of the animals, facilities, expertise of the people, and research goals) often make prescriptive (“engineering”) approaches impractical and unwarranted. Engineering standards are sometimes useful to establish a baseline, but they do not specify the goal or outcome (such as well-being, sanitation, or personnel safety) in terms of measurable criteria as do performance standards.
      “The engineering approach does not provide for interpretation or modification in the event that acceptable alternative methods are available or unusual circumstances arise. Performance standards define an outcome in detail and provide criteria for assessing that outcome, but do not limit the methods by which to achieve that outcome. This performance approach requires professional input and judgment to achieve outcome goals.” (Guide for the Care and Use of Laboratory Animals, p. 3)


Another important publication is the Guide for the Care and Use of Agricultural Animals in Agricultural Research and Teaching, published by the Federation of Animal Science Societies. This document does not have a direct regulatory connection, but is widely used by institutions, and AAALAC, in evaluating animal care and use programs in the agricultural setting. The Ag Guide includes general chapters on animal husbandry and the physical plant, but most of the husbandry and facilities discussion in the Ag Guide is contained in a series of chapters by species (e.g., “Guidelines for Beef Cattle Husbandry,” “Guidelines for Poultry Husbandry,” etc.)


Introduction to animal husbandry

In most research facilities these days, routine animal care is provided by a centralized service unit (e.g., a “Division of Laboratory Animal Resources”), typically in a geographically centralized facility; research staff usually are not responsible for either husbandry or maintenance of the facilities and equipment. Costs for providing this service may be covered by the institution, but more commonly, the Principal Investigator is charged a per diem rate (e.g., $0.50 per cage of mice per day) that s/he pays from a research grant or account. Per diem rates vary tremendously among institutions, based on just how much of the cost of the operation is recovered by this mechanism, compared with the degree of subsidy by the institution. It is important at the start of a research project, particularly in a new institution, to learn the institutional policies and procedures for maintaining research animals, and to meet both the animal care and office staff that will be responsible for providing animal care and use services. Some facilities may have a required orientation for new research staff.

The reading assignment does a good job of introducing laboratory animal husbandry and, hopefully, conveys the complexity and importance of these tasks. Looking after research animals is a lot more than feeding, watering and cleaning animals; it includes sanitation (cages, water bottles, floors, walls, etc.), daily observation of animals, monitoring and control of environmental conditions, handling of animals, and often, administration of treatments and sample collection (for either experimental or veterinary care purposes). Animal care staff are often certified by the American Association for Laboratory Animal Science.

Husbandry can easily be taken for granted, but controlling unwanted variation is much like “quality control,” and that means ensuring that all controllable variables are of suitable quality and consistency. For example, quality control of diets starts with professional evaluation of the feed manufacturer and whether they are providing feed of appropriate nutrient composition and freshness, and freedom from chemical and microbial contamination. Maintaining quality of feed after manufacture involves also the local feed supplier, as well as the research facility itself; storage of feed must avoid temperature extremes and prevent contamination of feed by pests. Other components of basic husbandry, such as bedding, drinking water, and sanitation, have similar quality control objectives, i.e., professional evaluation of manufacturers’ specifications and credentials, combined with in-house verification of product composition or performance.

The physical environment is another component of animal husbandry, and includes essentially all components of the animals’ immediate housing space (the primary enclosure or microenvironment) and the room (or outdoor) conditions outside the primary enclosure (macroenvironment). Enclosures must be safe and secure, but there also must be appropriate control of temperature, humidity, ventilation, illumination and noise, for both welfare reasons and to control unwanted variation.

The Guide includes a new section on “behavioral management,” which highlights the increasing awareness of animal well-being above and beyond basic biological needs for survival. The structural environment should include objects “…that increase opportunities for the expression of species-typical postures and activities and enhance the animals’ well-being.” While specific criteria of well-being aren’t known, there is an assumption that, when animals interact in a normal (species-typical) way with a cage enrichment, there may be a benefit to the animals’ well-being. Similarly, housing social animals with conspecifics and providing opportunity for activity may promote animal well-being.

The last section of Chapter 2 discusses “Population Management.” These issues are less directly linked to animal welfare, but are important for both regulatory purposes (e.g., there are certain requirements for identification and medical records under the AWARs) and to help ensure efficient use of animals in the research project. Individual animals do not always require identification, but there may be need to do so. This has become increasingly necessary in rodent research given the complexities associated with use of transgenic animals. Genetics and nomenclature are often overlooked, but can be vital. Genetic monitoring is just as important as health monitoring (see Unit Three) to help control unwanted variation.


Introduction to animal facilities design and operation

“A well-planned, well-designed, well-constructed, and properly maintained facility is an important element of good animal care and use, and it facilitates efficient, economical, and safe operation.” (Guide for the Care and Use of Laboratory Animals, p. 71)

Chapter 4 in the Guide provides a design perspective (“construction guidelines”) for much of the environmental issues raised above, but also speaks about “functional areas.” Well-designed animal facilities contain more than just animal rooms and, in fact, support space (procedure rooms, surgical and necropsy suites, cage wash areas, locker rooms and offices, and storage) may need as much space in the facility as the animal housing.

It is important to recognize that the design of an animal facility, or a renovation project, requires expertise, and that an animal facility has many features unique from typical office or even laboratory space. It is vital that experienced laboratory animal specialists and architects are involved in planning these expensive facilities. Under-budgeted or poorly-designed facilities can hinder or even prevent the provision of appropriate animal housing conditions and, ultimately, the control of unwanted variation that has been emphasized in this Unit.

Chapter 4 gives some of the basic design considerations for an animal facility, but there is clearly need for more detailed information. Appendix A in the Guide has some useful references, and one is the chapter referred to above (Hessler, JR and SL Leary. Design and management of animal facilities, pp. 909-953. In JG Fox et al. (eds.): Laboratory Animal Medicine, 2nd ed. Elsevier Science, 2002).


Study Questions

1. According to the AWARs, what size cage should be provided for a 4 kg rabbit? Under what circumstances could this minimum standard be adjusted?

2. According to the Guide, what is the recommended temperature range for a rat? Despite this wide range, what is said about daily fluctuations in temperature?

3. Find a web site for a supplier of laboratory animal feed. What features of quality control are evident from their listing?

4. According to the Guide, what are several specific construction guidelines for animal facilities that probably would not be part of the guidelines for a typical office building.


Discussion Questions

1. The Introduction to the Guide speaks about the value of performance standards. Some have criticized this approach, because it lacks clearly defined criteria. From a regulatory standpoint, are performance standards adequate to ensure animal welfare?

2. The Guide discusses so-called environmental enrichments – objects in the animal’s housing that would add to its well-being. Are there situations or conditions where the provision of enrichments might be detrimental?

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