Effect of plant development during first and second growth cycle on chemical composition, condensed tannins and nutritive value of three sainfoin (Onobrychis viciifolia) varieties and lucerne

Sainfoin (Onobrychis viciifolia) is a temperate legume that contains condensed tannins (CT), i.e., polyphenols that are able to bind proteins and thus reduce protein degradation in the rumen. Few studies have investigated the relation between plant phenology, CT characteristics and nutritive value of sainfoin. In this study we investigated differences among three sainfoin varieties (Esparcette, Ambra and Villahoz) that were of different geographical origin, and which were cultivated at the same site over the course of two growth cycles and compared with a tannin-free legume, lucerne (Aubigny). Plants were harvested on nine dates in the first and four dates in the second growth cycle. Phenological stages were analysed for leaf-to-whole-plant ratio, nitrogen (N), organic matter digestibility (OMd) by the pepsin-cellulase method, cell-wall concentration, N solubility (solN) plus CT concentration, biological activity and structures. Leaf-to-whole-plant, cell-wall concentration, N of sainfoin and lucerne were closely related to the phenological stage. Although sainfoin developed earlier than lucerne, its pepsin-cellulase digestibility was higher than or close to lucerne. Esparcette had the lowest OMd, N and solN and the highest CT concentration. CT concentration, proportion of prodelphinidins (PD) and mean degree of polymerization (mDP) increased with the phenological stage (or plant maturity), and these parameters were associated with lower biological activity of CT. Sainfoin varieties differed in their relationships between phenological stages, nutritional parameters and CT characteristics. The results demonstrated that sainfoin can be a valuable alternative forage legume to lucerne.