The chemical composition and digestibility of twelve plant samples (Arthrocnemum macrostachyum, Atriplex canescens, Artemesia herba-alba, Astragalus gombo, Calobota saharae Ceratonia siliqua, Gleditsia triacanthos, Hedysarum coronarium, Medicago sativa, Ononis natrix L, Hordeum vulgare and Stipa tenacissima L.) grown in arid and semi-arid areas of Algeria were evaluated (in 2010). Feed components were determined by proximate analysis whereas phenolic and tannin compounds were analyzed by colorimetric procedures. Digestibility was assessed by conventional gravimetric in vitro and in situ methods. In general, crude protein content in dicotyledon (dicots) species was always greater than that in monocotyledon (monocots) grass showing higher Neutral and Acid Detergent Fiber (NDF and ADF) and lower lignin contents than dicots. The tannin concentration varied considerably between species, but in general, the plants investigated in this study had low tannin contents (except for Ceratonia siliqua, Gleditsia triacanthos and Hedysarum coronarium). Monocots showed lower in vitro and in situ, fermentation rate and cumulative gas production than dicots species. This study indicated that a large reserve of plant species in the local flora is available that could be potentially used for livestock feeding. These feeds, if fully exploited, could assist in increasing the level of production and productivity of the livestock resources in the region. Manuscript profile