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Recognition and Alleviation of Distress in Laboratory Animals
normalcy, therefore, may or may not serve as clinical indicators of a disease state. Various transgenic and knockout mice that exhibit severe behavioral and physiological phenotypes appear abnormal relative to their control littermates, but are normal for their genotype. For example, it is appropriate to evaluate Huntington’s disease transgenic mice for signs of stress and distress only relative to their own “normal” behavior, taking into account their particular genetic makeup, their abnormal motor patterns, and reduced weight gain (Mangiarini et al. 1996).
BEHAVIORAL RECOGNITION OF STRESS AND DISTRESS
Many parameters have an effect on species-specific normal behavior andshould be taken into consideration when behavioral characteristics areused to determine normalcy or the presence of stress and distress. Animalsexhibit a variety of behavioral changes as part of the normal aging process.Males and femalesdiffer in the baseline values of many stress markers.Inbred murine strainsdiffer in almost every behavioral, sensory, motor,and physiological trait studied and each inbred strain may respond tostress differently. Similar behavioral differences in response to stress havebeen observed in primates.Genetically engineered phenotypesneed tobe considered when assessing stress and distress in transgenic and knockout animals. Thematernal environment and rearingexperiences of theoffspring affect their future responses to stress and distress. Special physiological states, such as impending parturition, are defined by state-specificbehaviors.Housingconditions may also modify species-specific behavioralpatterns. Behavioral normalcy is further characterized by theabsence ofbizarre or atypical patternsof species-specific behavior. The presence ofstereotypies usually implies suboptimal environments and possibly pooranimal welfare.
The identification of species-typical behavior often comes from ethograms developed by researchers to describe the kinds of behavior that animals display in various settings (Bronson 1979; for more references see Additional References). While the use of species-typical behavior as a normative benchmark has considerable value (Latham and Mason 2004), it does have limitations. First, the full range of species-specific behaviors cannot be recreated (or allowed to be expressed) in the laboratory animal care facilities as some types of behavior observed in natural settings (e.g., severe aggression) are clearly undesirable from a laboratory management perspective. Second, species-typical behaviors are neither invariant nor universal, as both the frequency and the presence of such behaviors vary