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The text on this page is taken from an informal compilation of opinions of contributors to the online VOLE List. As such, they are not peer reviewed and may contain differences of opinion. Those wishing to contact the list may contact Adrian Smith.

We are reviewing our acclimatisation period  for mice/rats as we currently have a rather vague policy of about a week between delivery from a commercial supplier and the start of non surgical procedures and about 2 weeks from delivery from a commercial supplier and the start of surgical procedures. I would be very  interested in knowing  what other policies other people have and if there are any publications to identify these periods.

We have the following recommendations 72h for minor procedures (e.g. blood sampling, injections etc) and 7 days for recovery surgery and came to think this should be acceptable and agree with the published work.

The following table covers some references we found around 4 of years ago to support this recommendation:

Table showing an overview of potential confounding physiological changes in rodents and rodents and rabbits following transport

Confounding physiological change Time to normalise

Altered serum electrolytes                                                                                1 day

Lymphopaenia, neutrophilia and reduced NK cell activity                                1 day

Immunosuppression: reduced delayed type hypersensitivity,

antibody production and haemagglutination titres                                             2 days

Altered behaviour (including food and water intake)                                         3 days

Reduced body weight                                                                                        4 days

Increased serum glucose                                                                                  4 -6  days

Increased plasma lipoproteins and muscle enzymes                                        7 days

Increased serum LH levels                                                                                 > 7 days

Reduced reproductive performance                                                                   30 days

The UK Rodent Refinement Working Party recommends a minimum of 5 days acclimatisation after transport. Our departmental managers posted a query recently on an Animal Welfare and Management Discussion Group to obtain views on this issue across animal units in the UK. From 13 replies received it was clear that all units applied an acclimatisation period and this was usually 5-7 days.

Here's a short extract from a paper the veterinarians at my establishment had to draft to support the recommended acclimatisation periods for our sites:

Immediate effects of transport

Stress activates the HPA axis leading to the release of corticosterone from the adrenal cortex. Raised levels of this hormone have been measured in the serum of rodents and rabbits subjected to transport. (Aguila et al. 1988a; Toth and January 1990). Corticosterone has widespread effects on physiological processes. One such direct effect is suppression of the immune system. Immunologic function tests have been performed in mice following transport that showed reduced delayed type hypersensitivity (using the footpad test), reduced antibody production (using the plaque-forming cell assay) and reduced haemagglutination titres (Landi et al. 1982). Aguila et al. (1988b) reported that corticosterone reduces NK cell activity in mice following transportation. Serum biochemistry, electrolyte and haematological parameters in rats subjected to transport returned to within normal levels by 12 days (Bean-Knudsen and Wagner 1987). The effects of transport stress on metabolic activities also appear to be long-lasting. Olubadewo et al. (1994) found significantly raised plasma lipoproteins and catecholamines in rats following transport and these levels did not return to normal until after 7 days.

There are varying reports on recovery from weight loss experienced by rodents (~5%) following transport. The body weights of rats were reported to return to normal after 3 days (Capdevila et al. 2006; Weisbroth et al. 1977; Wallace 1976; Dymsza et al. 1963) however those of mice tended to take longer. Mice subjected to transport had significantly altered behaviour (Tuli et al. 1995). They showed more exploratory behaviour, more aggressive behaviour, more feeding behaviour and less grooming, which mostly returned to normal by 3 days.

Weinert and Eimert (1994) found that the circadian corticosterone rhythm was disturbed in mice that experience a time shift upon transport. This rhythm was re-synchronized within 2 weeks in juvenile mice yet took over 2 weeks to recover in adults. Bieglmayer et al. (1980) reported that LH concentrations, but not FSH, were increased in rats following transport and did not return to normal for at least 7 days. Reproductive performance of rabbits requires one month to normalise (Hayssen 1998).


  • Obernier JA and Baldwin RL (2006). Establishing an appropriate period of acclimatization following transportation of laboratory animals. ILAR Journal 47:364-369.
  • Van Ruiven R, Meijer GW, van Zutphen LFM and Ritskes-Hoitinga J (1996). Adaptation period of laboratory animals after transport. Scandinavian Journal of Laboratory Animal Science 23:185-190.
  • Tuli JS, Smith JA and Morton DB (1995). Stress measurements in mice after transportation. Laboratory Animals 29:132-138.
  • Landi M, Bowman T and Campbell S (1988). Effects of handling and transportation stress on rodents. In: New Developments in Biosciences: Their Implications for Laboratory Animal Science, Beynen AC and Solleveld HA (eds), Martinus Nijhoff Publishers, Dordrecht, 449-457.

More references and guidance can be found in the PREPARE guidelines.