The impact of cage dividers on mouse aggression, dominance and hormone levels.

Home cage aggression in group-housed male mice is a major welfare concern and may compromise animal research. Conventional cages prevent flight or retreat from sight, increasing the risk that agonistic encounters will result in injury. Moreover, depending on social rank, mice vary in their phenotype, and these effects seem highly variable and dependent on the social context.

Using mice from different breeding sites fails to improve replicability of results from single-laboratory studies.

Theoretical and empirical evidence indicates that low external validity due to rigorous standardization of study populations is a cause of poor replicability in animal research. Here we report a multi-laboratory study aimed at investigating whether heterogenization of study populations by using animals from different breeding sites increases the replicability of results from single-laboratory studies. We used male C57BL/6J mice from six different breeding sites to test a standardized against a heterogenized (HET) study design in six independent replicate test laboratories.

Correction: Do multiple experimenters improve the reproducibility of animal studies?

[This corrects the article DOI: 10.1371/journal.pbio.

Handling method affects measures of anxiety, but not chronic stress in mice.

Studies in mice have shown that less aversive handling methods (e.g. tunnel or cup handling) can reduce behavioural measures of anxiety in comparison to picking mice up by their tail.

Systematic assessment of the replicability and generalizability of preclinical findings: Impact of protocol harmonization across laboratory sites.

The influence of protocol standardization between laboratories on their replicability of preclinical results has not been addressed in a systematic way. While standardization is considered good research practice as a means to control for undesired external noise (i.e.

The rearing environment persistently modulates mouse phenotypes from the molecular to the behavioural level.

The phenotype of an organism results from its genotype and the influence of the environment throughout development. Even when using animals of the same genotype, independent studies may test animals of different phenotypes, resulting in poor replicability due to genotype-by-environment interactions. Thus, genetically defined strains of mice may respond differently to experimental treatments depending on their rearing environment.

Do multiple experimenters improve the reproducibility of animal studies?

The credibility of scientific research has been seriously questioned by the widely claimed "reproducibility crisis". In light of this crisis, there is a growing awareness that the rigorous standardisation of experimental conditions may contribute to poor reproducibility of animal studies. Instead, systematic heterogenisation has been proposed as a tool to enhance reproducibility, but a real-life test across multiple independent laboratories is still pending.

Effects of weaning age and housing conditions on phenotypic differences in mice.

Poor reproducibility is considered a serious problem in laboratory animal research, with important scientific, economic, and ethical implications. One possible source of conflicting findings in laboratory animal research are environmental differences between animal facilities combined with rigorous environmental standardization within studies. Due to phenotypic plasticity, study-specific differences in environmental conditions during development can induce differences in the animals' responsiveness to experimental treatments, thereby contributing to poor reproducibility of experimental results.

Evaluation of the effects of space allowance on measures of animal welfare in laboratory mice.

We studied how space allowance affects measures of animal welfare in mice by systematically varying group size and cage type across three levels each in both males and females of two strains of mice (C57BL/6ByJ and BALB/cByJ; n = 216 cages, a total of 1152 mice). This allowed us to disentangle the effects of total floor area, group size, stocking density, and individual space allocation on a broad range of measures of welfare, including growth (food and water intake, body mass); stress physiology (glucocorticoid metabolites in faecal boli); emotionality (open field behaviour); brain function (recurrent perseveration in a two-choice guessing task); and home-cage behaviour (activity, stereotypic behaviour). While increasing group size was associated with a decrease in food and water intake in general, and more specifically with increased attrition due to escalated aggression in male BALB mice, no other consistent effects of any aspect of space allowance were found with respect to the measures studied here.

Effect of Cage-Induced Stereotypies on Measures of Affective State and Recurrent Perseveration in CD-1 and C57BL/6 Mice.

Stereotypies are abnormal repetitive behaviour patterns that are highly prevalent in laboratory mice and are thought to reflect impaired welfare. Thus, they are associated with impaired behavioural inhibition and may also reflect negative affective states. However, in mice the relationship between stereotypies and behavioural inhibition is inconclusive, and reliable measures of affective valence are lacking.

An Exploration Based Cognitive Bias Test for Mice: Effects of Handling Method and Stereotypic Behaviour.

Behavioural tests to assess affective states are widely used in human research and have recently been extended to animals. These tests assume that affective state influences cognitive processing, and that animals in a negative affective state interpret ambiguous information as expecting a negative outcome (displaying a negative cognitive bias). Most of these tests however, require long discrimination training.