Establishing an appropriate period of acclimatization following transportation of laboratory animals. 
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: (1) Will anticipated physiological changes confound the research to be conducted? ( 2) What is the length of time necessary for confounding physiological changes to normalize?  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 beta-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 1 to 7 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.