Determination of nutritional value and degradability of dry matter and cell walls of Astragalus crenatus Schult at different phenological stages in Hir-Neor rangelans of Ardabil province

This study was conducted with the aim of determination of chemical composition, degradability fractions and nutritional value of Astragalus crenatus Schult. Two sites with different elevation ranges (1500-1700 and 1900-2100 meters from sea level) were selected to collect the data in highlands ranges of Hir to Neor, Ardebil County. The data sampling was carried out in three phenological stages (vegetative growth, flowering and seeding stages). Plant samples were analyzed and their NDF and ADF were measured using Van Soest method. AOAC common lab methods were used to measure plant samples chemical composition. Ruminal degradability of samples was determined by in situ technique (e.g. two ruminal cannulated Moghani rams). The results showed that digestibility and degradability of dry matter, organic matter, NDF and ADF of samples from the site located in 1900-2100 meters from sea level ranges were significantly higher than the site in lower site (p<0.01). Moreover, the analysis of the collected samples showed that the NDF and ADF values in form of percentage of dry matter for species in higher elevations range sites were higher. The dry matter contents of plant samples differed significantly in various phenological stages (p<0.01). Results showed that the plant samples in vegetative stage had the highest ash and ruminal and post-ruminal digestibility in both sites. The plants in vegetative stage had lowest NDF, ADF and organic matter content compared to the other phenological stages. In conclusion, the degradability of dry matter of the species in vegetative growth stages was more than other stages, indicating that the nutritional value of plant species is reduced in flowering and seeding stages. It can be concluded that late spring is the best time for grazing this species and it can be considered in grazing management plans of the study area.