Transportation in Laboratory Rats: Effects of a Black Box

Abstract

Laboratory Animal Science is a multidisciplinary science contributing to the humane use and care of animals and to the quality of animal experiments. Animal staff, researchers and regulators strive continuously to improving welfare of animals used in research. Transportation of small laboratory rodents has thus far stayed mainly below the radar of their scrutiny. Not only does transportation directly affect the welfare of the animal, the effects of transportation on research results can lead to the wrong conclusions. Daily routine procedures with small laboratory rodents imply many stressors that cause temporary deviation from the animal’s (physiological) homeostasis. In stressful situations the animal will react in a different way to a stimulus as compared to how it would react in an unstressed situation. In that sense a stressful response of the animal may therefore bias research results. Those involved in animal research are at least aware that animals need acclimatization after arriving at their facility. However, the duration of this acclimatization period is seldom based on evidence-based research, even though the experts are clear in their warnings on the effects of transportation on research results. To acquire reliable data from transferred animals transfer stress can perhaps be ameliorated by implementing an acclimatization period between arrival and onset of the study. The studies presented in this thesis were designed to measure the effects of transportation on Wistar rats, a frequently used general purpose outbred strain of rats and the duration of these effects. The results might help to optimizing the transportation and acclimatization process, to improve the welfare of the animals and increase the validity of research results. By mimicking the daily practise used in animal transfer, the studies were set up to be translatable to other research fields. By means of radiotelemetry physiological measurements were performed on heart rate, blood pressure and locomotor activity. Effects on behaviour were studied by performing home cage observations on activity, social interactions and self-grooming. Blood samples were taken to measure the effects on plasma corticosterone, glucose and creatine kinase. Also bodyweight, body temperature and environmental temperature were taken into account. Overall, the results show that transferring rats from a breeder to a research facility significantly affects their physiology and behaviour. Some parameters seem to stabilize at a level different from initial baseline, which indicates allostasis rather than homeostasis. After two weeks, parameters that stabilize, have reached their (new) baseline level. Not all parameters do stabilize within two weeks. In corticosterone we’ve found highly fluctuating and continuously increasing levels in female rats. Therefore we cannot consider corticosterone a reliable indicator for acclimatization in adolescent female rats. Although affected by transfer, locomotor activity shows inconsistent durations of effect. Longer acclimatization possibly leads to stabilization of locomotor activity, which should be investigated further. Based on the longest allostatic stabilization found in the combined results of all studies in this thesis, an acclimatization period of two weeks would be advisable.