Hu, Y., Xu, L., Yang, F. et al. 2007. The effects of enrichment with music or colorful light on the welfare of restrained mice. Laboratory Animal and Comparative Medicine 27(2), 71-76.

Objective: To investigate the positive effects of four different forms of environmental enrichment on the welfare of mice subjected to restraint stress with the purpose of screening suitable enrichment. Method: Mice undergoing poor welfare due to repeated restraint were kept in different enriched environment (enriched by march, serenade, blue filter or red filter), food consumption and body weight gain were recorded throughout the study. Two weeks later all the animals were assessed for their stress level by measuring physiological parameters (body weight, food efficiency ratio[FER], thymus index, spleen index and total leukocyte in peripheral blood[WBC]) and biochemical parameters (serum levels of ACTH, CORT, β-EP, EPI, NE, IL-2, TP, GLU, TCHO). Result In restraint control group, restraint stress decreased their body weight gain, FER, WBC, IL-2, β-EP (P<0.01) and spleen index (P<0.05), while increased their ACTH, CORT, NE (P<0.01) and EPI (P<0.05). Compared to restraint mice, mice from blue light group and from serenade group exhibit lower levels of ACTH and NE (P<0.01), as well as the restoration level of β-EP (P<0.01) by blue light, indicating elevated neuroendocrine responses to restraint stress. With respect to the higher level of IL-2 (P<0.01), more WBC (P<0.01) and larger thymus index (P<0.01, compared to control group), blue light may contribute to relieve the inhibitory status in immune system induced by restraint. When comes to other groups, mice from red light group tended to eat more at daytime than at night compared to mice from restraint control group, and mice from march reduced their serum levels of CORT too much. Conclusion: Enrichment with either serenade or blue filter partly enhanced resistance to repeated restraint stress in mice, thus suggest that both forms of enrichment should be beneficial for the welfare of laboratory mice. However, the effects of march and red light are debatable and need more investigation.