Characterisation of tannins and in vitro protein digestibility of several Lotus corniculatus varieties Helena Hedqvist a , Irene Mueller-Harvey b , Jess D. Reed c , Christian G. Krueger c , Michael Murphy a,* a Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Kungsa Èngen Research Centre, S-753 23 Uppsala, Sweden b Department of Agriculture, The University of Reading, P.O. Box 236, Reading RG6 6AT, UK c Department of Animal Sciences, University of Wisconsin-Madison, Animal Sciences Building, 1675 Observatory Drive, Madison, WI 53706-1284, USA Received 7 March 2000; received in revised form 28 June 2000; accepted 11 July 2000 Abstract Seven birdsfoot trefoil (BFT) varieties (Lotus corniculatus) grown in Sweden, were harvested at the 50% ¯owering stage and analysed for tannins by the radial diffusion and HCl±butanol methods. The ¯avan-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 relative proportions of the higher molecular weight tannins. MALDI-TOF mass spectrometry of tannins from two varieties gave well-resolved spectra of tetramers, pentamers and hexamers. Oligomers up to the decamers were also detectable. Each of these oligomers had a subset of structures incorporating catechin/epicatechin (CE) and gallocatechin/epigallocatechin (GE) units. Some homopolymers containing CE units only (i.e. procyanidins), but none with GE units only (i.e. prodelphinidins), were detected. Most mixed CE/GE oligomers of all sizes contained one or two GE units. There were signi®cant differences (P  0:05) in vitro N-degradability between four varieties. The data suggest that degradability of the soluble proteins in birdsfoot trefoil were negatively correlated to tannin concentrations (R 2  0:93) despite the fact that their overall concentrations were very low. # 2000 Elsevier Science B.V. All rights reserved. Animal Feed Science and Technology 87 (2000) 41±56 * Corresponding author. Tel.: 46-18-67-16-31; fax: 46-18-67-29-46 E-mail address: michael.murphy@huv.slu.se (M. Murphy). 0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII:S0377-8401(00)00178-4