Acclimation of Rodents


Boston University is committed to observing federal guidelines and AAALAC international guidelines for the humane care and use of animals.

“Transportation unavoidably causes stress in animals. Although stress is not always an adverse experience and is a necessary and regular aspect of life, it causes changes in an animal’s physiological status during transportation and for some period thereafter. Utilizing transported animals before their physiological status normalizes can have considerable and unintended effects on research results.”1

Transportation refers to transportation from a vendor or from other institutions or campuses, including intracity, intercity, intrastate, interstate, or international and involves truck and/or air transport. This policy does not address intercampus transport.

Rodents acquired from approved vendors with defined health profiles do not require quarantine, but “newly received animals should be given a period for physiologic, psychologic, and nutritional stabilization before their use. The length of time for stabilization will depend upon the type and duration of animal transportation, the species involved, and the intended use of the animals.”10 This policy does not address quarantine.

In order to prevent additional stress to newly arrived animals and prevent confounding of research data due to the experimental animal not having regained homeostasis after shipping, Boston University has established the following policies for acclimation of newly arrived research rodents.


A. Shipping stress
Stress associated with being removed from a familiar background and surroundings and being exposed to numerous new experiences, including being packed in a shipping crate, new cage-mates, different food, transport noise, and temperature variations. “Transportation involves physical, physiological, and psychological stressors.”11

B. Acclimation (=Acclimatization)

  1. Becoming accustomed to new housing, food, water, handlers, cage-mates, noises, smells, light cycle, and other variables and regaining homeostasis.
  2. Physiological adjustment of an organism to environmental change (Merriam-Webster’s Collegiate Dictionary, 11th ed.).

Policies for Rodent Acclimation After Shipping

A. BU requires an acclimation period of 3 full days (72 hours) for rodents prior to any use for survival experiments.
B. If surgery or other major survival procedures or experiments are started on a Friday [because the animal(s) arrived the previous Tuesday], the responsible research staff must be prepared to check and care for the rodent(s) throughout the weekend (Saturday and Sunday).
C. Day-of-arrival use is allowed for terminal experiments (nonsurvival surgery, tissue harvest). However, the principal investigator is advised to consider the effect that shipping stress may have on the experimental data.
D. Rodents acquired from colleagues at other institutions or from colleagues at another BU campus are subject to the IACUC Policies for Transportation of Rodents and Quarantine of Rodents. Therefore, their period of acclimation will usually extend beyond the 72-hour time limit.


A. Factors affected by shipping stress and acclimation:

  1. “Stress associated with transportation has widespread effects on physiological systems in laboratory animals, including changes in the cardiovascular, endocrine, immune, central nervous, and reproductive systems. Although short-lived, these changes can confound research if animals are utilized before homeostasis is restored and physiological measures return to normal. Therefore, some period of acclimatization following transportation is generally suggested to restore homeostasis. The following two questions should be considered to establish an adequate period for acclimatization:
    • Will anticipated physiological changes confound the research to be conducted?
    • What is the length of time necessary for confounding physiological changes to normalize?
  2. Finding answers to those questions in the literature can be a challenge. Most literature on the physiological impact of transportation involves agricultural animals, although the limited literature in common laboratory animal species generally parallels changes documented in agricultural animals. The literature documents elevated heart rate and weight loss, as well as elevated concentrations of adrenaline, noradrenaline, glucose, cortisol, free fatty acids, and β-hydroxybutyrate. Carbohydrate, protein, and lipid metabolism (both lipolysis and lipogenesis) are altered, and plasma osmolality, albumen, protein, and pack-cell volume increase. Neutrophilia and lymphopenia are also evident. These measures generally return to baseline within one to seven days of transportation, although animals that are young, severely stressed, and have stress-sensitive genotypes may show altered physiological measures for several weeks. Other measures such as circadian rhythm and reproductive performance may take several weeks to months to normalize”. 1
  3. “Numerous studies demonstrate the beneficial effects of frequently handling research animals before initiation of study protocols as well as in early life”.12
  4. “Animals habituated to the handler or which are gentled in early life show less handling stress in later life and react only to the particular experimental stimuli used in the study, whereas nonhandled animals are much more likely to react to a new handler as well as to the test situation.” 13

B. Periods of acclimation exceeding three days may be required for certain studies. It is in the principal investigator’s best interest to ascertain how the studies undertaken are confounded by transportation stress. For example, it has been reported that subsequent to transportation:

  • Reproduction including reproductive hormones and behavior are affected for a significant period of time and affect adolescent rodents more 4, 5, 8
  • Immunologic functions are inhibited2
  • Corticosterone levels are elevated3
  • Serum chemistry parameters are affected3
  • Fetal brain development and response to toxins6
  • Heart rate, body temperature, and activity9


  1. Jennifer A. Obernier and Ransom L. Baldwin, 2007. Establishing an Appropriate Period of Acclimatization Following Transportation of Laboratory Animals. ILAR Journal 47(4).
  2. Landi, MS et al. Effects of shipping on the immune function of mice. Am J Vet Res 1982 Sep. 43(9):1654–7.
  3. Bean-Knudsen DE and Wagner, JE. Effect of shipping stress on clinicopathologic function in F344/N rats. Am J Vet Res 1987 Feb. 48(2): 306–8.
  4. Stewart J, Kolb, B. The effects of neonatal gonadectomy and prenatal stress on cortical thickness and asymmetry in rats Behav Neural Biol 1988. May, 49(3):344–60.
  5. Hayssen V. Effect of transatlantic transport on reproduction of agouti and nonagouti deer mice, Peromyscus maniculatus. Lab Anim 1998 Jan 32(1):55–64.
  6. Ogawa, T. et al Valproate-induced developmental neurotoxicity is affected by maternal conditions including shipping stress and environmental change during early pregnancy. Toxicol Lett 2007 Nov 174(1-3):18–24.
  7. Syversen E et al Temperature variations recorded during interinstitutional air shipments of laboratory mice. J Am Assoc Lab Anim Sci 2008 Jan 47(1):31–6
  8. Laroche J et al Reduced behavioral response to gonadal hormones in mice shipped during the peripubertal/adolescent period. Endocrinology 2009 Jan [Epub ahead of print]
  9. Capdevila, S et al Acclimatization of rats after ground transportation to a new animal facility. Lab Anim 2007, Apr 41(2):255–61.
  10. The Guide for the Care and Use of Laboratory Animals. NCR ILAR 1996, P.58.
  11. NRC [National Research Council], 2006. Guidelines for the Humane Transportation of Research Animals. Washington DC, National Academies Press.
  12. Conour, LA, Murray, KA and Brown, MJ 2006. Preparation of Animals for Research – Issues to Consider for Rodents and Rabbits. In Preparation of Animals for Use in the Laboratory. ILAR Journal 47(4):283–293.
  13. Tuli Js et al 1995. Stress measurements in mice after transportation. Lab Anim 29:132–138.

BU IACUC approved June 2009; reviewed January 2014