Many delays in the ARC review and approval process originate from inadequate answers to the Experimental Design and Justification Section of the Application to Use Animal Subjects in Research and/or Teaching. Therefore, the following information is provided in order to assist investigators in preparing a comprehensive yet concise description of the overall experimental design as required.

The Animal Research Committee (ARC) is comprised of scientific and non-scientific members alike. Therefore, investigators are required to prepare non-technical research summaries, comprehensible to all members, regardless of their backgrounds. In this vein, verbatim text from grant applications is considered inappropriate for this section. A well-written summary should provide the reviewer with a clear understanding of the procedures to be employed in the care and use of animals in the proposed research and allow for straightforward calculation of the number of animals needed for the study. While the entire experimental design need not be written using lay language, the description should be written in a manner such that it can be readily understood by a scientist outside your area of expertise. As such, highly technical terms should be avoided or clearly defined. Likewise, all acronyms should be defined as well. The following points should be considered in writing the summary:

  1. Describe the general experimental procedures to be carried out on the animals. Readers should gain an understanding of each procedure a research animal may undergo. Each investigator must use her/his best judgment as to the level of detail required; however, as a general rule, most descriptions of a single experiment should fit in one page. Of course, protocols involving highly complex or multiple studies will require additional text to be clearly understandable.
  2. Outline the surgical or non-surgical procedures only to the extent necessary to assist the reviewer in understanding the role of those procedures in the protocol and the number of animals that will undergo the procedures. A complete description of the procedures must be provided in the appropriate sections (e.g., Surgery, Non-Surgical Procedures, Physical Restraint) of the application.
  3. If the study involves behavioral modification through the use of electrical or other forms of stimulation, including light or sound, or deprivation of food and/or water, the methods to be used must be fully described. Provisions for ensuring the general well-being of the animals subject to such methods also must be described.
  4. If applicable, describe the dependent variables to be measured and identify the statistical methods by which the data will be analyzed.
  5. Clearly define the endpoint of the study. If the animal is expected to experience pain or distress as a result of a procedure, the earliest experimental endpoint should be selected to minimize the likelihood of pain or distress occurring. The ARC generally prohibits the use of death as an endpoint; rather, animals should be euthanized when judged to be ill or, when necessary, moribund. If the experimental design necessitates the use of death as an endpoint, a convincing scientific justification for withholding euthanasia from animals judged to be moribund must be provided. Refer to the ARC Policy on Death as an Endpoint for additional information.
  6. If the animals will be euthanized for tissue collection, provide a brief description of the analyses to be performed on the tissues.
  7. Indicate the total number of animals required to complete the study or for the next three years. The total should be easily derivable by summing the number of animals needed for all the groups. Additional animals included to account for replication, attrition, or for refining technical procedures should be mentioned explicitly.
  8. To the extent possible, assign all animals to experimental groups, which can be easily distinguished by the independent variables defining each group (e.g., drug dosages, time points, controls, etc.). In some cases a table may be useful. Assign the experimental groups to the appropriate pain categories, as defined in the Pain Category Assignments section. Animals used in non-survival surgical procedures, regardless of duration, must be listed in Category "D." Likewise, animals that will be anesthetized, even briefly for minimally invasive procedures (e.g., blood or tissue collection, or catheterization), must be listed in Category "D." Note: Animals that cannot be provided pain relief must be listed in Category "E" and scientific justification for withholding pain relief must be provided in the application.
  9. Clearly indicate the number of animals needed per group and explain how group sizes were determined, either (i) by statistical methods, or (ii) where statistics are not applicable (e.g., teaching labs, feasibility studies, antibody production, etc.), on the basis of other considerations (e.g., student/animal ratio, tissue yield per animal, antigen/animal ratio, prior experience, etc.). Note that rate of experimentation is not considered acceptable justification for the requested number of animals.

Examples of Experimental Designs

The following are provided only as examples of satisfactory answers to the Experimental Design and Justification for Requested Number of Animals..

Example #1
80 adult rats will be randomly assigned to one of four groups, each consisting of 20 animals. This group size is necessary to provide statistical significance at a level of p<0.05.

Group #1 - rats will be fed normal diet supplemented with mineral X
Group #2 - rats will be fed normal diet supplemented with mineral Y
Group #3 - rats will be fed normal diet supplemented by both minerals X and Y
Group #4 - control (rats will be fed normal diet)

The rats will be maintained on their respective diets for ## days, at which time they will be deeply anesthetized with sodium pentobarbital (80-120 mg/kg, i.p.) and perfused through the heart. Previous studies have shown that, in order to observe measurable differences in the levels of metabolites A, B, and C, the animals must be maintained on an altered diet for at least ## days. After euthanasia, heart, kidney, and liver will be removed for determination of levels of metabolites A, B, and C.

Example #2
This is a teaching course designed to instruct residents in standard microsurgery techniques. The techniques to be performed will be reviewed didactically by all course participants one day prior to the hands-on portion of the course. It is anticipated that the course will be offered once per academic quarter, and approximately 20 students are expected to enroll (60 students per year). The students will work in pairs, with each pair sharing one rabbit. Based on prior experience in offering the course, the instructors determined that this student/animal ratio will allow each student adequate practice performing the specific procedures being taught while at the same time minimizing the number of animals used. Thus, a total of 90 rabbits should be sufficient to offer the course for the next three years.

Just prior to the course, the instructors will anesthetize the rabbits with ketamine (45 mg/kg, i.m.) and xylazine (8.8 mg/kg, i.m.). The students will then take turns performing techniques Q, R, S, and T in sequence. The rabbits will be euthanized at the end of the 2 hour session with an overdose of sodium pentobarbital.