Abstract
A suboptimal housing environment such as small cage size can adversely influence many aspects of the biology of laboratory animals including their response in behavioral tests. However, the effect of cage size on the mental and physical conditions of Kunming mice, which have been widely used to develop models of depression, anxiety, and many other diseases in China, are still far from clear. The purpose of this study was to investigate the effects of cage size on reproductive ability, exploratory behavior, anxiety, and working memory of Kunming mice. Two cage sizes were used, including a standard cage (20 × 30 × 25 cm3) and a restricted cage (10 × 20 × 25 cm3). The results revealed that compared with mice in the standard cages, mice in the restricted cages showed: (I) a decreased delivery rate of dams (P < 0.05) and a lower survival rate of offspring (P < 0.05), specifically in females (P < 0.05); (II) a decreased exploratory behavior (P < 0.01) and an increased anxiety level (P < 0.01); and (III) higher working memory in the T-maze test (P < 0.05). These results indicated that a restricted cage size has detrimental effects on the reproductive ability and anxiety level, but its effect on cognitive ability is complex and warrants further study. In short, these results provide empirical evidence for better practices in caring for Kunming mice, with some cautions about the effects of cage size on behavioral tests.
Highlights
These results suggested that the restricted cage size led to a decrease in exploratory behavior and to an increase in anxiety in KM mice
We found that the reproductive performance, exploration activity, anxiety level, and working memory of KM mice are affected by cage size
Restricted cage size causes an increase in anxiety levels and an improvement in working memory
Summary
Much attention is being paid to the welfare of laboratory animals (Reeb-Whitaker et al, 2001; Gonder and Laber, 2007), and the conditions of keeping laboratory animals have been the focus of several studies, as environmental factors such as cage size may interfere with the results of behavioral tests (Loo et al, 2001; Mcglone et al, 2001; Wolfer et al, 2004; Julia et al, 2008). Previous studies have shown significant effects of cage size on reproductive performance (Julia et al, 2008; Whitaker et al, 2009), aggressiveness level (Loo et al, 2001), anxiety level (Bellei et al, 2011), and exploration and cognitive abilities (Forsyth and Young, 2007; Julia et al, 2008; Line et al, 2010). Mice in larger or smaller cages are all becoming more aggressive (Loo et al, 2001; Gupta et al, 2007; Buijs et al, 2011), but few studies mention the effect of cage size on cognition, especially working memory. The optimal cage size should be determined for a given species as well as different strains of a species
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