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National Research Council (US) Institute for Laboratory Animal Research. Guidance for the Description of Animal Research in Scientific Publications. Washington (DC): National Academies Press (US); 2011.

Cover of Guidance for the Description of Animal Research in Scientific Publications

Guidance for the Description of Animal Research in Scientific Publications.

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4The Research Animal Environment (Study Conditions)

The study conditions of the research animal environment can be difficult to succinctly describe but are critical to interpretation and evaluation (Reliene and Schiestl 2006). Numerous aspects of the animal facility environment can affect study outcomes, not all of which can be detailed in the materials and methods section (Clough 1982). Again, it is preferable to provide more rather than less specific information to enable other investigators to effectively assess and reproduce the research.

At a minimum, the description in the materials and methods section specifies the type of diet, housing, bedding, water, and general environmental parameters (e.g., temperature, humidity, lighting) with ranges.

Effective descriptions also include aspects of the animal facility environment that are known to affect the study type or endpoints. For example, in experiments with endocrine disrupters, leaching of estrogenic substances from plastic caging or water bottles, or phytoestrogen exposure in the diet, can affect study results, so it is appropriate to describe these factors in more detail than in other types of studies (Ashby et al. 2004; Everitt and Foster 2004; Hunt et al. 2003). Dosed-feed toxicity studies in rodents may be subject to experimental confounders from cross contamination by housing control cohorts and experimental groups in the same room, so a detailed description of caging, air flow, or handling procedures may be warranted. Similarly, fish used in toxicological studies may excrete metabolites into the water column that may affect cohorts in the same tank or fish in different tanks on the same filtration system.

4.1. Diet

Diet is a potential source of variation in many types of studies, so a detailed description of food and feeding methods is important to include for every study (Haseman et al. 2003; Newberne and McConnell 1980; Newberne and Sotnikov 1996; Nold et al. 2001; Rao and Crockett 2003). Diets vary in type, form, nutrients, caloric content, levels of contaminants, and methods of preparation, and each of these characteristics can affect the animals and the study results (Barnard et al. 2009; Ford and Ward 1983).

In addition to the frequency and method of feeding (e.g., ad libitum vs. portioned), effective reports include the type of diet, source, manufacturer, catalogue or batch number, dietary form, and any dietary supplements. Specialty diets, in particular, require detailed descriptions that may include handling and storage methods. Designations such as “standard laboratory chow,” “breeder chow,” “commercial dog food,” and “fish pellets” are never appropriate.

When experimental substances are added, a description of the methods of feeding (e.g., pair feeding) and dose determination is relevant; the presentation of food consumption data may be warranted in these cases. Information about food handling and preparation procedures, such as autoclaving or irradiation, is also useful as these may adversely affect the food (e.g., its nutritional quality, palatability, or shelf life; Anderson et al. 1981; Ford 1977; Twaddle et al. 2004; Zimmerman and Wostmann 1963).

For nutrition or metabolic experiments, an adequate description notes not only the specific feedstuffs (with nutrient and caloric content if customized diets are used and the reader cannot otherwise access such information) but also, when relevant, the extent and method of any dietary restriction because caloric intake affects many experimental parameters (Deerberg et al. 1990; Laroque et al. 1997; Masternak et al. 2005). Information about food contaminant levels, diet certification, or nutrient analysis is usually appropriate for nutrition or toxicology studies (Barnard et al. 2009; Newberne and Fox 1980; Newberne and Sotnikov 1996; Silverman and Adams 1983). For articles about endocrine-related research, readers will need detailed information about food handling procedures and the animals’ diet, especially in light of numerous reported differences between studies and between laboratories that study endocrine disruptor compounds (Brown and Setchell 2001; Heindel and vom Saal 2008; Muhlhauser et al. 2009; Naciff et al. 2004; Thigpen et al. 2003, 2004; Wang et al. 2005).

4.2. Water

Specific information about drinking water source, delivery methods, and treatments (e.g., acidification, chlorination, sterilization) is important to provide; some treatments, in particular, are known to affect certain experimental parameters (Bjornsson et al. 2003; Hall et al. 1980; Hermann et al. 1982; Merne et al. 2001). In certain types of studies water delivery methods have been known to be an important component of husbandry as well (Gordon and Wyatt 2011). (Water environment for fish and other aquatic species is discussed separately in the section on Aquatic Systems.)

4.3. Housing

Adequate descriptions of housing convey the physical, microbial, and social features of the animals’ proximate environment, including the following information:

  • the nature of the housing (controlled environment vs. outdoor), including temperature, humidity, lighting, with ranges;
  • type of caging (e.g., static vs. ventilated, filtered vs. unfiltered, style, composition, dimensions);
  • bedding and nesting materials (composition, amount, analysis);
  • cage complexity (enrichment);
  • housing paradigm (group/multiple vs. single);
  • method of cage handling (frequency and methods, aseptic transfer, methods of sterilization); and
  • nondomiciliary specialized housing such as metabolism caging, isolators, or inhalation exposure housing.

Taken together, these details will convey the animals’ microenvironment (including local microbial burden and air quality), which is influenced by numerous housing variables (Keller et al. 1989; Lipman 1999; Stark 2001). For example, the air quality in a rodent cage is affected by the type of cage (solid, filter-capped, ventilated), whether it contains direct contact bedding, the animals’ diet, and the number of animals (Keller et al. 1989; Krohn and Hansen 2002; Lipman et al. 1992; Macy et al. 2002; Memarzadeh et al. 2004; Rosenbaum et al. 2009).

Caging type, size, and composition can affect behaviors and physiologic responses (Abramov et al. 2008; Freed et al. 2008; Gordon and Fogelson 1994; Kallnik et al. 2007; Mineur and Crusio 2009; Stark 2001; Steplewski et al. 1987; Tsai et al. 2003).

Similarly, bedding type, manufacturer, source, treatment and storage before use, and quantity can be important because bedding is known to influence study outcomes through effects on the animals and/or their microenvironment, including through the presence of contaminants (Becker et al. 2010; Bohonowych et al. 2008; Buddaraju and Van Dyke 2003; Gordon 2004; Perkins and Lipman 1995; Potgieter and Wilke 1997; Potgieter et al. 1996; Rosenbaum et al. 2009; Sanford et al. 2002; Silverman and Adams 1983; Smith et al. 2004).

Growing international interest in the welfare of research animals has led to support for the provision of environmental complexity and enrichment and, when possible, the housing of research animals in socially compatible groups. These elements of the housing environment have many effects both known and unknown (Bayne 2005; Gortz et al. 2008; Haemisch and Gartner 1994; Jankowsky et al. 2003; Lawson et al. 2000; Tsai et al. 2002; Whitaker et al. 2009). To account for possible effects that might introduce variability in the results, it is important to provide detailed descriptions (including source information) about all cage additions, including nesting and other materials used for enrichment, in the materials section.

A description of the grouping of animals and details of their housing are relevant as a number of studies have reported dramatic differences in scientific outcomes based on single versus group housing (Andrews et al. 2000; Haseman et al. 1994, 2003; Nevalainen et al. 2007; Nyska et al. 1998).

The handling of cages—for example, the frequency and method of cage changing—can affect study outcomes (Burn et al. 2006; Vesell et al. 1976). If microbial status is important in an experiment, description of cage sterilization methods and aseptic cage changing methods may be warranted.

Because cage placement, both in rooms and on racks, has been associated with effects in long-term studies (e.g., for toxicity/oncogenicity or inhalation research), a description of methods to rotate cages on racks to minimize any environmental bias is useful (Herzberg and Lagakos 1992).

4.4. Macroenvironment

The macroenvironment of the animal room—temperature, humidity, lighting, ventilation—influences the microenvironment and therefore is relevant information (Dauchy et al. 2011; Rosenbaum et al. 2010). For most studies the materials section includes specifics such as temperature range, relative humidity range, and aspects of lighting such as the timing of light:dark cycles and dimming to mimic circadian cycles. Ambient temperature affects many research endpoints (Jhaveri et al. 2007; Swoap et al. 2004; Zhao et al. 2010), and relative humidity can directly affect animals and interact with other environmental parameters such as temperature to influence study outcomes (Ashida and Denda 2003; Diercks et al. 2010; Drickamer 1990; McJilton et al. 1976). Other aspects of the physical environment, such as sound, ventilation, and vibration, can affect the outcome of certain types of studies (NRC 2010, 45–47).

Discussion of the degree to which the animal environment was controlled and to what extent there was variance from the reported values will assist readers in interpreting and reproducing the results.

Copyright © 2011, National Academy of Sciences.
Bookshelf ID: NBK84203
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