The objective of this experiment was to study the impact of free-range pigs foraging on mountain pasture vegetation. Pigs (15 week-old, mean weight 50 kg, n = 25) were enclosed from June to mid-September in a 2-ha enclosure in the Jura Mountains (Switzerland) and fed with a mixture of lactoserum and cereals. The enclosure contained four different plant communities. Eutrophic pastures on deep soil were largely overturned, but recolonization was quick and vegetation dominated by the original species. Mesotrophic pastures were less damaged on stony soil but were completely destroyed on deep soil, recovery was slow and was characterized by a shift of plant species in a more eutrophic direction. Four years were not sufficient for complete recovery. Oligotrophic calcareous pastures on shallow stony soil were not damaged. The result of this study was that extensive breeding of pigs in mountain pastures are harmful to plant species in mesotrophic pastures, and should be restricted to less sensitive plant communities, with a rotation of two or three different sites.
Nomenclature: Lauber & Wagner (2000).