Restlessness behaviour, heart rate and heart-rate variability of dairy cows milked in two types of automatic milking systems and auto-tandem milking parlours

In order to assess the welfare of cows milked in automatic milking systems (AMS), restlessness behaviour during milking (stepping, foot-lifting), heart rate (HR) and heart-rate variability (HRV) were investigated in cows milked in two different AMS models (AMS-1, AMS-2) and in auto-tandem milking parlours (ATM) on four commercial farms in each case. Stepping rates and proportions of milkings with foot-lifting were calculated based on video recordings. Non-invasive radio equipment was used for measurements of HR and the HRV variable mean-squared differences of successive beat-to-beat intervals (rMSSD). HR data were recorded during milking and resting, thus allowing an assessment of the milking process in relation to the baseline level of each individual cow. Data were evaluated using generalised mixed-effects models. Restlessness behaviour was shown more often in AMS-2 than in AMS-1 and ATM. HR increased from resting to milking, and this difference was greatest in AMS-2. HR in AMS-1 and AMS-2 was higher during resting and milking than in ATM. rMSSD decreased from resting to milking, although to a lesser extent in AMS-1 due to lower values during resting. The lowest rMSSD values during milking were observed in AMS 2. In conclusion, statistically detectable differences in restlessness behaviour, HR and HRV indicated a slightly increased stress level in dairy cows in automatic milking systems as opposed to auto-tandem milking parlours. Viewed in absolute terms, however, all differences between the milking systems were