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Seven birdsfoot trefoil (BFT) varieties (Lotus corniculatus) grown in Sweden, were harvested at the 50% flowering stage and analysed for tannins by the radial diffusion and HCl–butanol methods. The flavan-3-ol composition of different BFT tannins was determined by HPLC. Tannins were isolated and examined for their molecular weight distributions by HPLC gel permeation chromatography (GPC) and MALDI-TOF mass spectrometry. Ruminal protein degradability was determined in vitro and related to tannin chemistry. Tannin concentrations of the BFT varieties were generally low and ranged between 0.3–1.0% (radial diffusion assay) and 0.2–1.7% (HCl–butanol assay) on a DM basis. The delphinidin:cyanidin ratios showed considerable variation ranging from 16:84 to 33:67 amongst the seven varieties. GPC analysis revealed small differences between the varieties with most of the variation occurring in the …