A preliminary survey on the occurrence of barbering in laboratory mice in Germany

Although barbering is common in laboratory mice ( Mus musculus), little is known about its effects, both on animal welfare and the research data collected from barbered mice. To gain information on the occurrence of barbering and related risk factors in animal facilities in Germany, we performed an online survey. All the respondents (n = 32 animal facilities) had experienced barbering in their facility. In most cases, less than 10% of the mice were affected, and the age of onset was mostly observed to be 2 to < 6 months. A greater susceptibility was reported in females and in C57BL/6 mice, but this could not be verified as the prevalence of females and the C57BL/6 strain was unknown. One facility reported differences in barbering between commercial animal suppliers. Barbering was also recorded in mice provided with enrichments, such as houses, wood-gnawing blocks, tunnels, running wheels/discs or cage dividers. None of the responding facilities provided swings, structural elements such as an elevated platform or foraging and cognitive enrichment. The questions of whether barbering may have an impact on study results and whether victims of barbering can be used for experiments revealed mixed opinions, most likely due to a lack of data on potential effects. This survey clearly demonstrated barbering to be a widely underestimated problem that is not given enough attention. We suggest that the occurrence of barbering should be systematically documented in every animal facility and reported in research articles, to provide a greater understanding of barbering and its potential effects.