Grazing and pasture management for biodiversity benefit

Abstract

The primary role of grazing animals in grassland biodiversity management is mainte- nance and enhancement of sward structural heterogeneity, and thus botanical and faunal diversity, by selective defoliation due to dietary choices, treading, nutrient cycling and propagule dispersal. Most research on dietary choices uses model systems that require considerable extrapolation to more com- plex communities. Grazing animals' diets are constrained by temporal and spatial changes in sward structure, plant defence mechanisms, herbage availability, plant phenology and animal physiological state. Potentially, these could be exploited to manipulate choice in diverse communities. Dietary choice differs between animal species, driven by factors such as body size, digestive physiology and dental anatomy. There is anecdotal evidence for breed differences but little experimentation, with ge- netic effects often confounded with background experience. There is information about landscape- scale breed and background effects but little about parameters such as bite and feeding station areas that allow reconstruction of the development of small-scale sward patchiness. An experiment at five European sites is examining breed effects on grazing behaviour, structural, floral and faunal diversity, animal production and economic impacts. In another project, calves are being reared by their own mothers or by cows of another breed allowing genetic effects on grazing behaviour to be separated from effects of early experience. 'Designer animals' may be needed to deliver desired grazing behav- iour and biodiversity outcomes, either by breeding or by the use of training and previous experience to manipulate choices. Application of research results requires consideration of conservation goals, whether at landscape, habitat, plant community or plant species level. There is a need to replace stocking rate prescriptions with sward-based methods and to integrate biodiversity goals into inten- sive systems. Major gaps in our knowledge of grazing behaviour and its impact on biodiversity re- main, necessitating greater integration of plant ecophysiology, plant community ecology and animal behavioural ecology research. grazing / biodiversity / pasture management / dietary choices / animal type