Background. Although population housing is recommended by many animal management and ethical guidelines, the effect of collective housing of mice of different age groups on mouse behavior has not been clarified. Since the development of the central nervous system continues to occur before sexual maturation, the stress of social ranking formation among male individuals in mixed housing conditions can affect postmaturation behavior. To assess these effects, sexually immature mice of different ages were housed in the same cage and a series of behavioral tests were performed after maturation. Results. The findings for three groups of mice—junior mice housed with older mice, senior mice housed with younger mice, and mice housed with other mice of the same age—were compared. Junior mice showed higher body weight and activity as well as lower grip strength and anxiety-like behaviors than other mice. In contrast, senior mice showed lower body temperature and increased aggression, antinociceptive effect, and home-cage activity in the dark period in comparison with other mice. Conclusions. Thus, combined housing of immature mice of different age groups affects mouse behavior after maturation. Appropriate prematuration housing conditions are crucial to eliminate the uncontrollable bias caused by age-related social stratification.

中文翻译：

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成熟前不同年龄组小鼠的集体住房影响小鼠行为

背景。尽管许多动物管理和伦理准则都推荐人口住房，但不同年龄组小鼠的集体住房对小鼠行为的影响尚未阐明。由于中枢神经系统的发育继续发生在性成熟之前，混合住房条件下男性个体社会等级形成的压力会影响成熟后的行为。为了评估这些影响，将不同年龄的性未成熟小鼠圈养在同一个笼子中，并在成熟后进行一系列行为测试。结果. 比较了三组小鼠的研究结果——与年长小鼠一起饲养的幼鼠、与年轻小鼠一起饲养的老年小鼠以及与其他同龄小鼠一起饲养的小鼠。与其他小鼠相比，初级小鼠表现出更高的体重和活动，以及更低的握力和类似焦虑的行为。相比之下，与其他小鼠相比，老年小鼠在黑暗时期表现出较低的体温，并增加了攻击性、镇痛作用和家笼活动。结论。因此，不同年龄组的未成熟小鼠的联合饲养会影响成熟后的小鼠行为。适当的早产儿住房条件对于消除与年龄相关的社会分层造成的无法控制的偏见至关重要。