Integration with livestock

Livestock systems have seldom been covered by the scientific literature on agroecology. Extensive grazing systems are based on the management of plant biodiversity by means of the grazing behaviour and mobility of herds adapted to harsh environments. Such systems usually have a higher net primary productivity, soil N cycling and C sequestration compared to unmanaged grasslands. These low-productive systems recycle nutrients efficiently and use mostly biotic processes (e.g. biological N fixation, tannin-rich plants for gastro-enteric parasite control) rather than chemicals. However, they are vulnerable to climatic variability and land degradation especially in drylands. Improved grazing management can lead to pasture restoration, while the use of species rich grass-legume mixtures, organic fertilizers and mixed grazing allows for sustainable pasture intensification. Nevertheless, further intensification may generate large losses to the environment of nutrients and greenhouse gases, since intensive grazing uncouples the C, N and P cycles that are tightly coupled in extensive pastures. Above a threshold animal density, sustainable intensification can only take place through increased livestock integration with crop ping systems. Integration with crop production (i.e. providing grains and crop residues as feed and returning organic N and other nutrients to arable land as manures) can raise the overall efficiency and productivity of agricultural land while enhancing landscape diversity and connectivity, thereby enhancing synergies across food production, biodiversity and other ecosystem services. Further recycling benefits may occur through optimization of the manure chain using technological options, such as anaerobic digestion and com posting. Industrial ecology can also be adapted to rethink indoors livestock systems (e.g. recycling crop residues and by-products, using natural microbial phytases to increase feed- P digestibility by pigs) and to develop integrated systems (e.g. combining livestock, crops and fish ponds as in South Asia) that are based on the niche complementarity of animal species. Through these examples, we discuss how theories in ecology can be applied to the design and management of livestock based agroecosystems. (Texte intégral)