428 Platform Speaker: Nutrients and plant secondary compounds in pasturelands and their ecological services.

摘要

Grazing-based livestock-production systems are between a rock and a hard place— where they experience increasing societal pressures to reduce environmental impacts in a world that demands increased and sustained productivity. Recent advances in understanding the nutritional ecology of herbivores may contribute to alleviate these seemingly contradictory endeavors. Forages are nutrition centers and pharmacies with vast arrays of primary (nutrients) and secondary (pharmaceuticals, nutraceuticals) compounds (PSC), which can provide multiple services vital for agroecosystems. Legumes with different types and concentrations of cell walls and with high concentrations of cell contents (e.g., birdsfoot trefoil, sainfoin, cicer milkvetch), coupled with different types and concentrations of PSC (e.g., hydrolizable and condensed tannins, terpenes) create a diverse foodscape with potential to enhance livestock nutrition, health and welfare relative to grasses, other legumes or pasture monocultures. In the process, livestock learn to forage these PSC-containing plants and their combinations, leading to reductions in methane and nitrogen emissions and to improvements in meat quality. Condensed tannins from sainfoin and saponins from alfalfa and from manure of cattle consuming these forages also reduce nitrogen mobilization in soils, reducing leaching and increasing plant-available nitrogen stores for future use. The challenge for future grazing-based livestock-production systems entails the provision of the “ideal” chemically diverse forages for a specific ecoregion in optimal temporal and spatial scales and sequences such that sustainability is achieved without compromising the ability to meet the production levels and ecological services described above.