Location of Growth Influenced Birdsfoot Trefoil Tannin Accumulation, but Few Accessions Differed in Tannin Concentration.

The USDA Natural Resources Conservation Service has noted that 75% of the tall fescue stands in the U.S. are endophyte-infected (E+). The deleterious effects of the endophyte can be diluted by providing access to other forages, particularly nutrient-rich legumes. The tannins produced by the temperate legume birdsfoot trefoil not only prevent bloat but can increase ruminant meat and milk production and quality. Moreover, there is evidence that tannins interact directly with alkaloids, benefiting ruminants grazing E+ tall fescue. A study was initiated with the long-term goal of creating a cultivar of birdsfoot trefoil well-adapted to the Eastern Transition Zone, where E+ tall fescue is commonly grazed, as well as to other U.S. climate regions. One objective of this study was to screen birdsfoot trefoil germplasm accessions with desirable traits for their tannin concentrations when grown in Utah, Michigan and Alabama. 133 accessions were germinated from seed in Conetainers® and two replications of 10 plants of each accession were transplanted to the field in June of 2014. In 2015, entire stems of surviving plants were composited by accession within replication, oven-dried, and ground to pass the 1-mm screen of a Wiley mill. The tannin concentration was determined using a butanol-HCl-acetone-iron assay in which ground plant material is heated to 70 °C for 1.5 h with mixing. Isolated birdsfoot trefoil tannins were used as the standard. Tannin concentrations were less for plants grown in Utah than for the same germplasms grown in Michigan and Alabama; tannin LS means were 18.39, 23.73 and 25.14 mg g^-1 DM for Utah, Michigan and Alabama, respectively. However, for 92 of the 113 accessions, there was no difference in tannin concentration among locations. While the higher-tannin accessions were not agronomically strong, several accessions with moderate tannin concentrations had exceptionally good establishment and production.