Protein and Dry-Matter Degradability of European- and Mediterranean-Derived Birdsfoot Trefoil Cultivars Grown in the Colder Continental USA

Recent work suggests several European- and Mediterranean-derived cultivars of birdsfoot trefoil (BFT, Lotus corniculatus L.) are well adapted to the colder continental United States and produce forage with greater condensed tannin (CT) concentrations, but comparable neutral detergent fiber (NDF) and slightly lower crude-protein (CP) concentrations than the commonly grown cultivar Norcen. In the current study, thirteen of these foreign-derived cultivars and Norcen were harvested under two-or three-cut management during 2006 in Michigan, Utah, Wisconsin, and West Virginia and analyzed in vitro for rumen degradable and undegradable protein on a CP and dry-matter (DM) basis (RDP CP, RDP DM, and RUP DM) and for rumen degradable and true degradable DM (RDDM and TDDM). Foreign-derived cultivars usually produced forage with greater RUP DM and lower RDP CP, RDP DM, RDDM, and TDDM than Norcen. The low NDF cultivar Bokor uniquely combined high CT and RUP DM with high TDDM. The highest yielding cultivar Lotar also produced herbage with moderate to high CT, RUP DM, and TDDM. Concentrations of CT and CP influenced RDP CP, RDP DM, and RDDM, while CT affected RUP DM, and fiber components influenced TDDM; relationships were greatly influenced by growth environment. Reductions in RDP DM exceeded gains in RUP DM as CT increased, thus, feeding of high-CT cultivars could mainly curb urinary N excretion from excess RDP DM rather than boost amino acid supply from potentially digestible RUP DM. Additional work is needed to improve the nutritional consistency of harvested BFT across environments and to develop higher-yielding cultivars with optimal RDP DM and RUP DM and high TDDM for maximizing livestock performance.