Potential stress reactions of dairy cows caused by an energy-related failure of automatic milking systems (AMS) are presented in this study. It was carried out on four commercial dairy farms in Germany, 2014. All farms were using 1 Lely AMS for about 60 dairy cows. 12 adult Fleckvieh were randomly selected per farm. The cows under observation were given 6 days to get used to a daily routine. From the 7th to the 9th day a video baseline of the behaviour was taken. On days 10 to 13 a power cut was simulated and the behaviour video-taped again. A list with 19 behaviour parameters was created and statistically analysed. Locomotion, rumination and elimination behaviour tended to occur more often in the experiment. Differences were observed in the determined duration: a longer duration was measured in four parameters, a shorter duration in two compared to the basal measurement. In conclusion, the individual animal behaviour of a cow during the simulation of power blackouts is altered. However, a significant difference was only measured in two out of 19 parameters. Based on a new statistical hypothesis test for high-dimensional paired samples it could be investigated that the probability for the event that with a probability of higher than 0.54 behavioral changes of the milk cows occur, equals only 0.05. Parameters such as cortisol content, heart rate variability and paces may be included into this evaluation to record and emphasise individual animal reaction regarding health and stress. The results of this research project and all other test results will be part of the sub-project animal- machine interaction within the concept approach "Integrated dairy farming - stable 4.0".