Tosa, N., Yoshimatsu, K., Arikawa, J. 2011. Effect of environmental enrichment after the occurrence of wet bedding created by mice and abnormal fur in mice. American Association for Laboratory Animal Science [AALAS] Meeting Official Program, 779-780 (Abstract #P161).

In management of laboratory animals, wet bedding created by mice and abnormal fur in mice cause problems on housing, leading to negative effects both on the wellbeing of mice and on the validity of experimental results. Most studies have investigated whether environmental enrichment (EE) prevents those problems by adding toys in advance. However, strategies for EE after the occurrence of those problems have not yet been established. In this study, we investigated the effect of giving toys after the occurrence of wet bedding created by mice and abnormal fur in mice. The cage was judged as containing wet bedding when more than 10% of the bedding was saturated with water for 14 consecutive days. The wet bedding was considered to have been created by some behavior of mice, because there was no equipment failure of automatic watering system valves provided outside the cage. To determine the effectiveness of giving toys, a piece of wood and a mouse house were added as EE to 62 cages judged as containing wet bedding after the cages were changed. After adding toys, the cages were changed at least once a week and bedding conditions were checked once a week on the standards of judgment. Fourteen days after adding toys, the number of cages containing wet bedding was reduced to 42 (66.1 %). The mice housed in the cages were as follows: female or male C57BL/6, ICR, BDF1, and genetic recombination mice. There were some obvious differences among sexes (P < 0.01) and strains (P < 0.01) in reduction of the frequency. The frequency decreased dramatically for male mice (42.1%) compared with that for female mice (76.7%). The most effective reduction was found in male ICR mice (0%). We also investigated the effectiveness of adding toys after the occurrence of abnormal fur (that is, loss of hair along with scratches). The toys were placed in 8 cages in which the mice were judged as having abnormal fur on scoring by visual assessment. The abnormal fur in mice improved after giving toys in all of the cages (100%, P < 0.01). Statistical analyses were carried out by analysis of nonparametric test. These results suggest that adding toys for EE after the occurrence of wet bedding and abnormal fur is effective for reducing the frequency of those problems.