A note on eating behaviour of dairy cows at different stocking systems-diurnal rhythm and effects of ambient temperature

This experiment was aimed at studying the diurnal rhythm of dairy cows eating behaviour at different stocking systems, and quantifying the effect of daily ambient temperature on this diurnal rhythm. In two experiments carried out in the summer of 2003 in The Netherlands, eight dairy cows were offered fresh pasture of perennial ryegrass. In the first experiment, four cows were given access to 1 ha pasture under a continuous stocking system (CSS), whereas, in the second experiment, four cows were given access to 528 m2 of a pasture daily, under a 1-day strip grazing system (SGS). In both experiments, grazing behaviour was measured repeatedly using jaw recorders. Under CSS, dairy cows had the longest meal at the evening, whereas under SGS, they had the longest meal in the afternoon. Under both systems, bite rate was maximal and chewing rate minimal during the evening bout. Dairy cows reduced their daylight eating time when maximum daily ambient temperature exceeded 25 °C. Bite rate and chewing rate were not influenced by management or ambient temperature. It appears to be possible to influence the timing and length (duration) of grazing bouts by management, mainly by changing the timing of allocating the new plot. However, it seems to be harder to influence the daily rhythm in bite rate and chewing rate, as both appeared not be influenced by ambient temperature or management.