GPS tracking indicates high variability in grazing patterns of lactating cows in Alpine summer farms

Understanding grazing patterns is necessary to manage semi-natural grasslands for both productivity and conservation of biodiversity with the associated Ecosystem Services. This study used GPS tracking to characterize the daily movement patterns and use of Alpine pastures by lactating Brown Swiss cows in three summer farms located at an average elevation of 1,900 m a.s.l. (SD: 90) in the eastern Italian Alps. Herd management was similar for all summer farms. Each day, after the morning milking in the barn, cows were driven to graze in different areas of the pastures, where they were then left free until the return to the barn for the evening milking, after which they were again released free to spend the night outdoor. From July 5th to September 5th in 2019 and 2020, 12 and 10 lactating cows per each farm, respectively, were equipped with GPS ‘collars’ scheduled to collect a position every 2 minutes. After editing data to exclude individual milking periods in the barns and outlier positions, the total daily distances walked by cows were on average close to 7 km but ranged from less than 2 km to around 15 km, varying greatly between dates, but also farms and years, mostly in relation the farmers daily decisions for grazing areas. Slopes steeper than 30° were very seldom used, most likely reflecting the cows choices of single movement steps. The total surface used by the cows of each summer farm (average: 211 ha; SD: 29 ha) varied by 4 to 30% between years, because of pasture patches being used only in one year. Internal use of such surface was highly heterogeneous: the quartile of surface with the lowest locations density contained <1% of total locations, while that with the highest density contained around 80% of the locations and was concentrated in the proximity of the barns. Use of high-frequency GPS tracking outlined the great variability of movement patterns and pasture use of the cows in the extensive conditions of Alpine summer farms, and helped to outline the role of farmers and animals choices. This knowledge is necessary to assess movement costs for the animals, and the fine scale spatial distribution of animals load and potential impacts on the grazed area.