Are the effects of different enrichment designs on the physiology and behaviour of DBA/2 mice consistent?

Abstract

SummaryEnvironmental enrichment is intended to improve the well-being of laboratory animals. Although many researchers have indicated that environmental enrichment may enhance animal well-being, there is some evidence that enrichment differs in its effects on physiology and behaviour between species and strains. The present study focuses on the effects of different enrichment designs on the physiology and behaviour of male and female DBA=2 mice. A total of 48 DBA=2J mice, 24 males and 24 females were used for this experiment. Upon arrival at about 3 weeks of age, the animals were randomly allotted to three experimental groups: NE, non-enrichment; E1, enriched with nest box, wooden climbing bar and nest material according to Scharmann (1993); E2, enriched with horizontal and vertical dividers, modi ed from Haemisch and Gä rtner (1994). Same-sex groups of four mice were housed for 12 weeks in type III Makrolon cages with (E1 or E2) or without (NE) enrichment objects. Behavioural performance (Open Field, Food Drive and Elevated Plus Maze tests) and physiological traits (haematological variables, body weight and organ weights, corticosterone and thyroxine levels) were measured. This study observed that enrichment had signi cant effects on the mean values of body weight (females), Open Field and Food Drive tests. The most signi cant housing differences were found between the E2 and NE=E1 groups. Furthermore, sex differences in the NE, E1 and E2 groups were not consistent for several variables (growth rate, relative weights of spleen, kidney and heart, Food Drive and Elevated Plus Maze behavioural performance). There was often a higher coef cient of variation (CV) in the E1 and E2 groups as compared to the NE group, chie y in physiological traits and in the Open Field and Food Drive tests. The results of this study indicate, that the effects of enrichment designs used in the present study are not consistent, but vary according to sex and the variable studied.

Effects of Spatial and Cognitive Enrichment on Activity Pattern and Learning Performance in Three Strains of Mice in the IntelliMaze

“…In studies where enriched animals received toys and nesting material as enrichment, the locomotor counts of female B6 mice in the open field were lower for the enriched groups (Dahlborn 1996;Yee et al 2007). Locomotor activity was also lower in D2 female mice which received enrichment consisting of a shelter and a climbing toy, but increased when the enrichment consisted of vertical and horizontal dividers (Tsai et al 2003). Performance of both B6 (a different substrain) and D2 mice in a food seeking task was shown to be improved by exposure to an enriched environment (Henderson 1976).…”

“…Broadly, environmental enrichment incorporates both inanimate and social factors which promote enhanced sensory, cognitive and motor stimulation (Rosenzweig andBennett 1996, Mohammed et al 2002;Olsson and Dahlborn 2002;. The effects of physical enrichment on behavioral data variation have been inconstant when applying different enrichment designs (Tsai et al 2003). However, other authors showed that, for female mice, environmental enrichment, in the form of more space, additional resources, increased complexity, and novelty, has a consistent effect on behavioral variables across laboratories and does not increase the proportion of Strain*laboratory variance (Wolfer et al 2004).…”

The effects of enrichment novelty versus complexity in cages of group-housed rats (Rattus norvegicus)

“…The results show clear differences between rats experiencing complex and novel housing also been demonstrated to denote good welfare in laboratory rats (Manser, 1992;Blanchard et al, 1995;Haller et al, 1998;Tsai et al, 2003;Živkovic et al, 2005). Similarly, aggression, non-aggressive social interaction, awake non-active behaviours, away from enrichment, underneath hopper and audible vocalizations have been used to judge the welfare of laboratory rodents with elevated levels being indicative of a generally compromised welfare state (Adams, 1977;Vivian and Miczek, 1993;Marashi et al, 2004; see also Fureix and Meagher 2016).…”

Does lack of enrichment invalidate scientific data obtained from rodents by compromising their welfare?

“…(ILAR 1996, 52) Some scientists have raised concerns that environmental enrichment may compromise experimental standardization by introducing variability, adding not only diversity to the animals' behavioral repertoire but also variation to their responses to experimental treatments (e.g., Eskola et al 1999;Gärtner 1999;Tsai et al 2003;Bayne 2005). (ILAR 1996, 54) Since it is critical that experimental outcomes are accurate and reproducible, it is important that the data obtained from rodents correctly represent the actual (average) response(s) to whatever perturbation is under investigation.…”