Abstract Information on nutritive values of each plant part in each phenological stage could help range managers choose suitable grazing times to achieve higher animal performance without detriment to vegetation. Thus, nutritive value of different plant parts of four species in three phenological stages (vegetative, flowering and seed production) from two sites was investigated. Species included: Sanguisorba minor, Onobrychis transcaspica, Onobrychis radiata and Astragalus brevidens. Forage quality was evaluated based on crude protein (CP), acid detergent fiber (ADF), dry matter digestibility (DMD) and metabolizable energy (ME) contents. A completely randomized design with a factorial arrangement of species and phenological stage was analyzed with five replicates. The results of chemical analysis indicated that there were significant differences among different phenological stages of various species in terms of their properties. As the plant ages increased, CP, ME and DMD decreased and ADF increased. Significant differences were obtained between forage quality of diverse species (p<0.01). There were significant differences between CP contents among forbs species (P < 0.01). High ADF percentages were obtained in Astragalus brevidens (47.59%). Low ADF contents were in Sanguisorba minor (36.9%). Astragalus brevidens exhibited the lowest DMD (50.7%). Metabolizable energy ranged from 6.61 for Astragalus brevidens to 7.87 MJ/kg for Sanguisorba minor.

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