The welfare of conventional stock laboratory mice has been assessed in 46 UK animal units using an expert-defined welfare assessment protocol containing 119 measures of mouse welfare. These were recorded using a questionnaire and observations made during a one-day visit to each unit. The standard of mouse welfare was considered to be good with widespread use of substrate and nesting material and space allowances in most cases well above the minimum recommended levels. Education and training was available and encouraged by the majority of animal units. The health and welfare of laboratory mice was being frequently assessed by animal care staff using daily inspections/observations, health records, and health monitoring schemes. Overall the mice assessed could be considered to be in good health, as indicators of poor health and welfare were exhibited at low levels, and the mice were observed exhibiting a wide range of positive natural behaviours. A number of environmental conditions (humidity, noise and light intensity) were outside recommended ranges in some animal units. The provision of cage resources such as shelters, gnawing material, floor food and other enrichment items were found to be variable. A high proportion of the units surveyed housed at least some of their mice (mainly males) singly and handling of mice by care staff varied between units. In some units there may be an opportunity for some staff to improve in some aspects of mouse handling. Finally, a number of interesting correlations were found between various behaviours and potential indictors of abnormal health or welfare, which require further investigation.

A Delphi consultation process was used to examine the validity and feasibility of potential resource-input and animal-based outcome measures of laboratory mouse welfare identified by a comprehensive literature search. The consultation was an iterative two-stage technique that used web and email based questionnaires to gather data. On completion of the second consultation stage a total of 97 measures of mouse welfare, their order of importance, and appropriate sample sizes and sampling times where relevant, were identified. Of these, 55 were resource-input measures that included assessments of the cages, animal rooms environmental conditions, husbandry procedures, provision of food and water, staffing, resources placed into mouse cages, and the establishment policies. The remaining 42 were animal-based outcomes, measures that included assessments of unprovoked behaviour, provoked responses, vocalisations, physical appearance, and health indicators. The measures that were considered by the experts to be appropriate for assessing laboratory mouse welfare measures can be placed into four basic categories: characteristics of the staff, performance of husbandry and care procedures, health and well-being of the mice, and the provision and use of cage resources.