Animal feeding in the arid and semi-arid regions during the dry season is largely dependent on cereal crop by-products and herbaceous plants, which provide poor feed and have low nutritive value. Research is directed towards the possibility of using on-farm produced feeds as feed supplements to meet some nutrient requirements of ruminants. Nutritive and anti-nutrient contents in leaves of some tree species (Melia azesarach, Pinus halepansis,Eucaliptus camaldulensis,Acacia ampliceps,Elaeagnus angustifolia, Casuarina equisetifolia, Sesbania aculeate, Schinus molle,Olea europea) and agricultural by-products were determined. The crude protein values ranged from 43 to 234 g/kg DM, with the leaves of E. angustifolia having the highest value and sunflower seed shells having the lowest value. Crushed date palm kernels had high (P < 0.05) contents (g/kg DM) of total carbohydrates (878), cellulose (441) and hemicellulose (280) and low contents of lignin (25), and could therefore be used as an energy-rich feed supplement for ruminants. The highest values (41–84 g/kg DM) of tannins were noted in the tree leaves of C. equistifolia, A. ambiceps, E. camaldulensis, S. molle, S. aculeate and P. halepansis. Nitrogen solubility in the leaves of the studied tree species was negatively correlated with total phenols and tannins. The leaves of the studied tree species (with the exception of P. halepansis), olive cake pulp, olive tree pruning branches and leaves of olive oil extraction are suitable as protein feed supplements for ruminants in arid and semi-arid regions.