Evolution of yield and quality of sainfoin (Onobrychis viciifolia Scop.) in the spring growth cycle

Sainfoin is a perennial legume with high dry matter (DM) yield during spring growth. The aim of this work was to study the evolution of forage yield and nutritional characteristics over a three-year period. Samples were collected at progressive morphological stages, from vegetative to seed pod. The mean stage by weight (MSW), yield, DM content, crude protein (CP), NDF, condensed tannin, gross energy (GE), organic matter digestibility (OMD) and the net energy for lactation (NEL) were determined. The forage characteristics were regressed on the growing degree days (GDD) and the MSW. The DM yield increased from 0.5 to over 8 t/ha as the growth stage progressed from vegetative to flowering, while the leaf to stem ratio decreased from 8 to 0.3 and the CP from 280 to 130 g/kg DM. The NDF ranged from 230 to 502 g/kg DM and was highly related to the GDD with a R2 of 0.92. The OMD decreased with increasing GDD without any differences over the years (R2 = 0.83). Unexpectedly, the codified morphological stage was unable to predict the OMD evolution, as the code scale was not sensitive enough to describe structural variations that affect the crop over the bud stage to flowering.