the stressors facilitates avoidance, minimization, and alleviation of distress, if such interference is not incompatible with the objectives of the research protocol.
A variety of strategies to refine the research protocol can help minimize animal stress and distress. A thorough literature review is vital for a critical analysis of the suitability, applicability, and validation of the proposed methodology. This section addresses the importance of correct statistical methods on the number of animals used. Choosing an earlier stage for an intervention (mild severity) or employing a different approach to arrive at the same research objective might work as effectively as waiting for later impacts of high severity and substantial distress. Examples of less stressful approaches include not allowing a tumor to grow to the point that it affects mobility before starting an experimental treatment, replacing long fasts as a motivating factor with the work-by-reward method, selecting a smaller stimulus to elicit a response before high-intensity stimuli are employed for the evaluation of a novel analgesic, and keeping the withdrawal of food and water in learning experiments to the minimum time necessary (Morton 1998; Morton and Hau 2002; NRC 2003a).
If a potential source of distress is the data-gathering or sample collection process itself, a less invasive method may be appropriate. For example, if the experimental design justifies it, the one-time surgical implantation of vascular lines and sensors can replace manual restraint for frequent blood collection or other physiological measurements, to avoid repeatedly subjecting the animal to stressful experiences (proper aseptic techniques and frequent peridermal maintenance is required when handling such surgical implants; for more information see chronically instrumented nonhuman primates in Broadbear et al. 2004). This is a common strategy for animals in chronic studies. However, it may be necessary to strike a balance if repeated surgery is necessary in order to replace batteries or sensors (Hawkins et al. 2004; Morton et al. 2003). Obviously, the constraints of the study will determine the appropriateness of alternative techniques, which may not be suitable for some types of studies or housing systems (Vahl et al. 2005).
Further examples of less stressful options (more information on the severity of stress caused by these methods is included in Chapter 3) include the use of oral or rectal swabs, plucked hair, or tissue from ear punches in place of tail tip amputation for the purpose of genotyping (Hawkins et al. 2006; Pinkert 2003; Robinson et al. 2003), and the measurement of cortisol