Can access to an automated grooming brush and/or a mirror reduce stress of dairy cows kept in social isolation?

In dairy farming, social isolation of cattle is commonly practiced for husbandry procedures such as artificial insemination, claw trimming and at times, for provision of medical treatment. When isolated, cows express physiological and behavioural signs of stress, such as elevated heart rate, hypothalamic-pituitary-adrenocortical activity and increased vocalisation rate. The aim of this study was to examine whether enriching the environment of the isolation pen using both tactile (i.e. an automated grooming brush) and visual (i.e. a mirror) stimulation could alleviate stress induced in socially isolated dairy cows. Eighteen cows (9 lactating and 9 dry cows) were subjected to four isolation conditions of 30 min each; isolation in the presence of a mirror, in the presence of an automated grooming brush, in the presence of both a mirror and an automated grooming brush, and in a non-enriched environment (without brush and mirror) that served as a control condition. Physiological (heart rate and heart rate variability) and behavioural indicators of stress (locomotion, vocalizations, attempts to escape the isolation pen and ear position of the cows) were measured during three phases throughout the isolation period (0-5 min, 10-15 min, 20-25 min). Our results show that, first, the heart rate of cows kept in social isolation, as well as the time cows spent in locomotion and exploration of the pen, decreased throughout the isolation period, regardless of treatment. Second, the presence of an automated grooming brush, a mirror or both an automated grooming brush and mirror in the isolation pen was not associated with reduced indicators of stress (physiological and behavioural measures) compared to the non-enriched environment. The results of our study are not in agreement with the findings of previous studies showing reduced levels of stress among socially isolated heifers/cows kept in the presence of visual enrichment (i.e. mirror/picture of a conspecific), and illustrate the need to further explore practices to reduce stress during social isolation.