Der optimale Erntezeitpunkt für tanninhaltige Futterpflanzen

Summary

Depending on the concentration in which they are fed, condensed tannins (CT) can have various beneficial or detrimental effects on ruminants. In organic farming the anthelmintic effects of CT are of special interest. In an outdoor experiment, the sea-sonal dynamics of the CT concentration of the harvestable biomass was investigated as a function of the biomass allocation to leaves and stems in Onobrychis viciifolia, Lotus corniculatus and Cichorium intybus in the course of a vegetation period in Zu-rich, Switzerland. Such knowledge is indispensable for a practical application of tan-niferous plants in farming systems. In line with our expectations, CT concentrations were higher in leaves than in stems and the leaf fraction of the harvestable biomass decreased steeply with time in all investigated plant species. In contrast to our expec-tations, within 20 weeks from sowing, the concentration of CT in leaves approximately doubled in Lotus (from 2 to 5% of DM) and in Onobrychis (from 5 to 9% of DM) and was nearly stable in Cichorium (0.5% of DM). Over time, the effect of the declining proportion of leaves in the harvestable biomass was almost exactly neutralized by the increasing concentration of CT in leaves, resulting in close to constant CT concentra-tions in the harvestable biomass during the season. We conclude that among the investigated species, the tannin concentration in Onobrychis seems most promising for the application against gastro-intestinal nematodes. As the CT concentration of harvestable biomass was found to be constant during the season, an optimal time for harvest can be determined in relation to agronomic properties such as fodder quality and yield.