Influence of maturity stage of forage grasses and leguminous on their chemical composition and in vitro dry matter digestibility

In this study we investigated the effect of maturity stage on chemical composition, in vitro dry matter digestibility (IVD) and volume of gas produced at 24 h (G24) of forages from Avena sativa L. (oats), Trifolium alexandrinum (berseem), Vicia sativa L. (vetch), Avena sativa-Vicia sativa (OV) and Avena sativaTrifolium alexandrinum (OB) mixtures collected at progressive morphological stages (S1, S2, S3, S4) from the emergence to the beginning milky maturation of the grain and the pod stage. Lowest CP content (56 g/kg DM) was recorded for A. sativa-T. alexandrinum at the mature stage (S4), whilst V. sativa collected at young stage (S1) had the highest content (274 g/kg DM). NDF content varied from 423.8 g/kg DM to 760.9 g/kg DM, and ADF content varied between 291.5 g/kg DM (vetch-oat) and 462 g/kg DM (vetch collected in S3). For all studied species the highest IVD coefficient (>0.800) corresponded to forage sampled at young maturity stage (S1) and the lowest values (0.500) to mature stage (S4) of Gramineae and mixtures. The same trend was followed by G24. It is pertinent to mention that for all studied species with increasing maturity CP content, IVD and G24 declined linearly while NDF and ADF contents followed an opposite trend. It was concluded that CP, IVD and G24 of Gramineae (oat) can be enhanced by its association with leguminous specially vetch, the most common combination in Tunisian agricultural systems.