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Switchgrass (Panicum virgatum L.) cultivars with improved forage quality would fill a forage gap during summer when hot dry weather reduces production of cool-season forages on marginal lands of the northeastern United States. 'Cave-in-Rock', 'Trailblazer', 'Shawnee', and 'Pathfinder' switchgrass hays were harvested and baled from field plots at Rock Springs, PA, on 29 June 2007, 16 June 2008 (Cut 1), and 8 Aug. 2008 (Cut 2) and fed to mature wether sheep. In 2008, Trailblazer was unavailable so Pathfinder was substituted. Morphological development stage and leaf and stem proportions were determined at each harvest, In 2007, cultivars did not differ in digestion of dry matter (DM) or fiber constituents and sheep consumed switchgrass hays similarly. In 2008, sheep consumed hay of switchgrass cultivars similarly but consumed more of Cut I than Cut 2 hay. Cut 1 hay also had greater neutral detergent fiber (NDF) and hemicellulose digestibility than Cut 2 hay. Shawnee consistently had lower DM, fiber, and crude protein digestibility (CPD) than Pathfinder in both cuts. Switchgrass cultivars selected for improved DM disappearance in vitro did not have greater DM or fiber digestion compared with Cave-in-Rock when fed to sheep. Differences among cultivars in nutritive value and in vivo fiber and DM digestion mostly were due to differences in plant maturity and leaf-to-stem ratio. doi: 10.2135/cropsci2010.03.0126

Tanniferous forage plants can have beneficial effects on ruminant productivity and health (improved protein supply, bloat safety and antiparasitic properties). However, condensed tannins can also lower palatability, voluntary feed intake and digestibility. The aim of our interdisciplinary project was to generate basic knowledge on plant management, feed palatability and the antiparasitic properties of tanniferous forage plants for their practical application in agronomy, focusing on their usefulness in controlling gastrointestinal nematodes in organic farming. We found that Onobrychis viciifolia (sainfoin), Lotus corniculatus (birdsfoot trefoil) and Cichorium intybus (chicory) were suitable for cultivation under the given temperate climatic conditions, whereas Lotus pedunculatus (big trefoil) was soon outcompeted by unsown species. Growing the tanniferous plant species in a mixture with Festuca pratensis (meadow fescue) rather than in a monoculture had the advantage of increasing total dry matter (DM) yield (especially in the case of tanniferous legumes) and of reducing the DM proportions of unsown species. However, due to dilution by non-tanniferous F. pratensis, the tannin concentrations of mixtures were clearly lower and the seasonal fluctuations in tannin concentrations greater than that of monocultures. Across species, tannin concentrations were highest for O. viciifolia, followed by L. corniculatus and very low for C. intybus. Palatability of all tanniferous forages was comparable to that of a ryegrass/clover mixture when fed as dried forage and, when offered as silage, palatability of O. viciifolia was clearly superior to that of the respective ryegrass/clover control. Administration of dried or ensiled O. viciifolia reduced parasite egg counts in feces of lambs co-infected with the gastrointestinal nematode species Haemonchus contortus and Cooperia curticei. We conclude that O. viciifolia is the most promising among the tested tanniferous forage plant species due to its suitability for cultivation, its high tannin concentration, its high palatability and its antiparasitic activity even in dried or ensiled form. Key words: condensed tannins, proanthocyanidins, forage cultivation, yield, silage, palatability, gastrointestinal nematodes, parasite control, sheep