Grooming using brushes in cattle: A review of benefits, influencing factors, and monitoring opportunities

Grooming in cattle serves important functions in maintaining hygiene and social relationships. Brushes are provided on farms as environmental enrichment to facilitate grooming. It has been suggested that brushing, as a behavior not necessary for survival, declines in association with illness and could thus serve as welfare indicator. However, an overview of the scientific evidence about optimal brush provision and their role in improving and monitoring welfare is missing. This review 1) synthesizes evidence on cattle brush use across production systems while identifying main influencing factors, 2) evaluates associations between brush use and welfare, and 3) outlines monitoring tools and areas for further research on the role of brushing in welfare surveillance. Cattle are motivated to use brushes, which improve coat hygiene, and may promote relaxation. However, evidence on the benefits for production traits such as milk yield or weight gain is limited. Brush use is sensitive to time and energy constraints; however, the evidence regarding changes in response to illness is inconclusive. While some studies reported suppressed brush use in association with lameness, respiratory disease, or metritis, responses depend on disease severity, environmental context, and the brush use variable considered, and not all studies found a difference between healthy and sick cattle. Brush use levels also vary across healthy groups and individuals according to production stage, housing system, and dominance, underlining the need for individualized baselines for welfare assessment. Further evidence is needed to clarify in which settings brushes help induce or monitor positive welfare. Integrating automated measures of brush use into welfare assessment and behavioral studies could help refine its role in welfare improvement and surveillance.