Nicholson Anthony, Malcolm Rachel D, Russ Phillip L, Cough Kristin, Touma Chadi, Palme Rupert, Wiles Michael V
The Jackson Laboratory, Bar Harbor, Maine, USA.
J Am Assoc Lab Anim Sci. 2009 Nov;48(6):740-53.
Increased numbers of mice housed per cage (that is, increased housing density) is seen as 1 way to reduce the costs of conducting biomedical research. Current empirically derived guidelines are based on the area provided per mouse depending on body weight as documented in the Guide for the Care and Use of Laboratory Animals. The current study aimed to provide a more scientific basis for housing density by examining the response of C57BL/6J and BALB/cJ mice to increased housing density from weaning to 5 mo of age, to determine those parameters most useful for future larger-scale studies. A wide range of phenotypic characteristics--including growth rate, body composition, hematology, serum biochemistry, hormone and metabolite measurements, in-cage telemetry, behavior, and cage microenvironment--was examined at various time points. The parameters showing greatest changes were: growth rate, which was significantly reduced in animals at the highest density; adrenal gland size, the proportion of adrenal cortex, and concentration of fecal corticosterone metabolites, all of which were increased at higher densities; and anxiety and barbering, which were more pronounced at higher densities. Cage microenvironment deteriorated with increasing density, but the increases in measured parameters were small, and their biologic impact, if any, was not apparent. The current findings indicate that mouse housing density can be increased 50% to 100% above the current recommendations (as floor area per mouse) with no or few apparent affects on mouse overall wellbeing. However, weight gain, fecal corticosterone metabolite levels, and barbering differed significantly with housing density and therefore are suggested as good measures of the response to alterations in housing.
每笼饲养的小鼠数量增加（即饲养密度增加）被视为降低生物医学研究成本的一种方法。目前基于经验得出的指导方针是根据《实验动物饲养和使用指南》中记录的每只小鼠根据体重所需的面积制定的。本研究旨在通过研究C57BL/6J和BALB/cJ小鼠从断奶到5月龄时对饲养密度增加的反应，为饲养密度提供更科学的依据，以确定那些对未来大规模研究最有用的参数。在不同时间点检查了广泛的表型特征，包括生长速率、身体组成、血液学、血清生物化学、激素和代谢物测量、笼内遥测、行为和笼内微环境。变化最大的参数有：生长速率，在最高密度饲养的动物中显著降低；肾上腺大小、肾上腺皮质比例和粪便皮质酮代谢物浓度，在较高密度下均增加；以及焦虑和拔毛行为，在较高密度下更为明显。笼内微环境随着密度增加而恶化，但测量参数的增加幅度较小，其生物学影响（如果有的话）并不明显。目前的研究结果表明，小鼠饲养密度可以比目前的建议（以每只小鼠的占地面积计）提高50%至100%，而对小鼠的整体健康没有或几乎没有明显影响。然而，体重增加、粪便皮质酮代谢物水平和拔毛行为随饲养密度有显著差异，因此建议将其作为对饲养环境变化反应的良好指标。
