Grazing behaviour of domestic ruminants according to flock type and subsequent vegetation changes on partially improved heathlands

The management of different livestock species may promote different vegetation dynamics that will affect subsequent animal performance and the sustainability of extensive grazing systems. The grazing behaviour of two livestock species (domestic cattle and sheep) under two different managements (monospecific or mixed with goats), and the subsequent vegetation changes were studied on mechanically cleared heathlands (Ulex gallii Planchon-Erica spp.), with one third of the total area improved with perennial ryegrass-white clover pasture (Lolium perenne L.-Trifolium repens L.). Results showed that animals in mixed herds spent more time grazing than in monospecific groups. Goats spent more proportional time grazing on shrubland (68%) compared to sheep (35%) and cattle (19%), which spent most of the time on the improved pasture. The diet composition estimates also confirmed that these two animal species basically selected herbaceous species (89-95%) whilst gorse was an important element of goats" diets (28%). Throughout the experiment, an increment of gorse cover, height and phytomass was observed, especially under single grazing; whereas dead matter and herbaceous covers decreased more under single than under mixed grazing. Besides, heather percentage and gorse height underwent a higher increase under cattle than under sheep grazing. On the improved areas the sward height was significantly higher with cattle, and the gorse sprouting was more controlled under sheep grazing treatments. It is concluded that the complementary grazing of goats can enhance the utilization of these heterogeneous plant resources, providing a more efficient way for both productive and environmental goals than single cattle or sheep grazing.