Plasma oxytocin in dry dairy cows after using a mechanical brush.

Mechanical brushes are a common feature in loose housing systems for dairy cows and are suggested to be linked to positive welfare, yet the physiological effects of brush use remain unexplored. This study examined the influence of cows' mechanical brush use on plasma oxytocin (OT) levels and explored its relationship with which body regions were brushed by the cow. We predicted that this self-grooming would lead to an OT increase, suggesting calming effects and pleasant feelings from brush use similar to those found from gentle tactile stimulation in other mammals. Additionally, we expected an influence of the body region brushed, given previously documented heart rate and behavioral differences from allogrooming different cow body regions. Twelve dry (nonlactating) cows were observed, with 3 blood samples taken before and after brushing, during which each cow had sole access to a mechanical brush. Results showed that OT levels in the sample taken within the 2 min following brush use were higher than baseline value, but only in younger cows with ≤2 previous lactation periods. The increase was small but may be of biological relevance. Additionally, OT changes varied by the brushed body region, highlighting the importance of this factor in future studies investigating cows' brush use in relation to positive welfare.