The impact of bedding volumes on laboratory mice
Publication Type: |
Journal Article |
Year of Publication: |
2017 |
Authors: |
Jennifer Freymann, Ping-Ping Tsai, Helge Stelzer, Hansjoachim Hackbarth |
Publication/Journal: |
Applied Animal Behaviour Science |
Keywords: |
bedding volume, body temperature, corticosterone, food intake, mice, preference test |
ISBN: |
0168-1591 |
Abstract:
Environmental refinement is considered to be an improvement in housing conditions for laboratory animals. Previous preference tests showed that female BALB/c and C57BL/6 mice prefer deeper bedding in comparison to shallow bedding (Freymann et al., 2015). In order to give a comprehensive insight into the impact of bedding depths on laboratory mice, we continued to examine the influence of three different bedding volumes (0.5 l, 1.5 l, 6 l) on the preference of male mice (experiment 1), home cage behaviour (experiment 2) as well as body temperature, food intake, food conversion efficiency (gram food intake per gram weight gain), intra-cage ammonia and corticosterone levels (experiment 3) of females and males. Experiment 1 used an automatic system to assess the preferences of male BALB/c and C57BL/6 mice. The bedding volumes were tested in pairs, which resulted in three test conditions (A = 0.5 l vs. 1.5 l; B = 0.5 l vs. 6 l; C = 1.5 l vs. 6 l). The results revealed significant preferences for cages containing large bedding volumes (test conditions A, B: p < 0.0001 for both strains; C: p = 0.0110 (BALB/c), p = 0.0511 (C57BL/6)). The second experiment analysed the home cage behaviour of female and male BALB/c mice between 18:00 − 20:00 (CET) using instantaneous sampling. No significant differences regarding the behavioural patterns locomotion, grooming, agonistic interaction, feeding, drinking, nest-building, resting, digging and burrowing were detected. However, animals housed on shallow bedding (0.5 l) engaged more in nest-building behaviour compared to groups housed larger volumes (1.5 l or 6 l). Experiment 3 demonstrated that bedding volumes (0.5 l, 1.5 l or 6 l) have profound effects on mice’s physiology. BALB/c and C57BL/6 mice kept on deep bedding showed higher body temperatures (p < 0.05 (0.5 l compared to 1.5 l, or 6 l)), lower food intake p < 0.01 (6 l compared to 0.5 l, or 1.5 l) as well as reduced intra-cage ammonia levels compared to groups on shallow bedding. In addition a larger bedding volume increased food conversion efficiency and reduced corticosterone levels in female mice. The trend became particularly obvious in female BALB/c mice (p < 0.05 (0.5 l compared to 1.5 l, or 6 l) for both parameters). Our results underline the importance of a sufficient amount of cage bedding in the husbandry of laboratory mice.