Neglected impact of routine. Refinement of experimental procedures in laboratory mice

Abstract

The concept of refinement is one of the major issues in the field of laboratory animal science and aims at reducing the incidence and severity of painful, distressing or discomforting procedures applied to laboratory animals. In this thesis, it was argued that the term refinement should be extended beyond its original meaning: besides the aim to minimise pain and discomfort, refinement should also entail the effort of experimenters to obtain the best possible results from their animal experiments or, in other words, to acquire reliable and valid data. Laboratory animals are subjected to many procedures which are part of daily routine. The studies presented in this thesis were performed to gain a further insight into the acute physiological stress response in laboratory mice (Mus musculus) caused by such routine experimental procedures. These acute stress responses should be taken into account when collecting data, as they may well influence results. It was investigated whether (i) environmental factors, which are generally believed to have a significant influence on the outcome of experiments, influenced this acute stress response and had the potential to diminish it; and (ii) how this could be assessed by the use of physiological parameters like heart rate (HR) and body temperature (BT) as measured by radio-telemetry. The studies were designed to mimic common laboratory situations and/or to be easily applicable in laboratory settings. After a first experiment had confirmed the applicability of HR and BT as quantitative parameters of acute stress, by comparing them with the validated stress hormone corticosterone (CORT), the following series of experiments established that certain environmental factors did indeed influence this acute stress response, whereas others showed no or little effect. Individual housing, cage enrichment and the announcement of restraint followed by reward were found to have a significant impact on HR and BT after routine procedures such as restraint by hand or injections, but the experimenter performing the routine procedure, the daily handling regime, the effect of reward following restraint without a preceding cue or the presence of rats in the mouse room were not found to show a detectable influence. The results did not indicate habituation of the mice to the routine procedures, but neither long-term effects of the procedures could be found. The acute stress responses all seemed to fall within the adaptive abilities of the mice, and the routine procedures performed in this thesis are therefore not considered to cause lasting harm, and as such are no major challenge to the well-being of the mice. However, the results of the current studies have illustrated the relevance of further research to evaluate the effects of routine procedures and the impact of environmental factors. For now, it can be stated that basal values of HR, BT or CORT should not be assessed directly after the animals have been subjected to routine procedures, and a recovery period of at least one to two hours is recommended.