Foraging behaviour and occupation pattern of beef cows on a heterogeneous pasture in the Swiss Alps

In the Alps, many summer pastures are under-used due to the decreasing number of livestock. Optimizing the grazing management of heterogeneous pastures implies a better understanding of foraging habits of cattle. The aim of this study was to precise the relationships between cattle behaviour and the characteristics of the vegetation. The experiment was carried out on a pasture encroached by shrubs (mainly Alnus viridis) and composed of four contrasted vegetation units at 1800 m a.s.l. Four beef cows were monitored in a paddock of 2.9 ha by Differential Global Positioning System (DGPS) during three rotations, in order to analyze the spatial and temporal occupation pattern. The open grasslands and, to a lesser extent, the tall herb community were significantly more visited than expected if cattle had foraged at random. The shrubby areas were far less visited than expected at random. The monitoring also revealed differences across rotations. Vegetation surveys were also performed to determine the specific contribution and the grazing frequency of the encountered plant species. The most eaten herbaceous plants were not necessarily those known to be the most palatable, even if graminoids were more selected than other plants. Leontodon hispidus, Agrostis capillaris, Festuca rubra, and Luzula sylvatica were the most selected species, whereas Veratrum album and Trollius europaeus were completely avoided. The consumed forage was of better quality than the forage collected at random and its nutrient content showed less variability and remained more constant over the three rotations. The results highlight that the selection processes exerted by cattle are important. They occur at different levels (species, vegetation type, in time) and confirm that an integrative approach is necessary for improving the understanding of cattle foraging behaviour in heterogeneous mountain pastures.