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 2 species in 3 phenological stages (vegetative, flowering, and seed production) from 2 sites was investigated. Species included: Haloxylon aphyllum and Eurotia ceratoides. 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 5 replicates. The result of chemicals analysis indicates that there were significant differences among different phonological stages of various species in terms of theirs properties. As the plant ages were increased, CP, ME and DMD are decreased while ADF was increased. Significant differences were obtained between forage quality of divers species (p<0.01). There is not significant difference between flowering and growth stages in view point of their CP, ME, DMD and ADF, it seems that this stage could be considered as favorable time for Haloxylon aphyllum and Eurotia ceratoides utilization by livestock.

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