Non-invasive physiological indicators of welfare in dairy cows.

Indicators of dairy cow welfare are important for the future assessment and improvement of cow welfare on-farm. The objective of this study was to investigate three categories of non-invasive physiological parameters as potential indicators of welfare in dairy cows, namely cumulation of cortisol in the hair, variability in heart rate (HRV), and variability and composition of milk yield, while taking personality traits into account. These indicators were assessed when cows (all primiparous; n = 48) were housed under reference conditions and when exposed to either improving or worsening housing conditions (weekly changes over the course of six weeks). The worsening housing led to an increase in heart rate and a decrease in milk yield. The housing effects on HRV and other milk-derived indicators, however, were affected by the personality traits of activity, fearfulness and sociability. Less active cows, less fearful cows and less social cows all displayed increases in HRV in the improving housing, but more active cows showed against expectations increased HRV in the worsening housing. More fearful cows showed increases in daily milk fluctuations in the worsening housing. These results point to HRV and milk-derived indicators, the latter of which are often routinely collected and that in addition to being non-invasive are also non-intrusive, as providing interesting physiological indicators of dairy cow welfare which will warrant further research.