The objective of this works was to evaluate a proper supplementation based on the seasonal availabililty of food to improve the sustainability of herbivore livestock systems. First feeding behaviour and food intake in grazing of five local rams in a native plain grassland in the north-east of Algeria were studied for three consecutive seasons: autumn, winter and spring. Meanwhile, the botanical composition and nutritional value of both the grazed meadow and the simulated animal bites (method of hand plucking) were evaluated. The identification of plant species ingested, however was done in springtime, the only season suitable for this operation. Animals preferred asphodel (Asphodelus microcarpus) (70 %), followed by legumes (20 %) and grasses (10 %). During the three seasons, the rams have selected a ration of better quality than the available forage (15.2 % CP, 0.79 UFV/kg DM and 14.5 % CP, 0.71 UFV/kg DM for spring). The amount ingested daily was maximum in spring (1.24 kg) and minimum in winter (689 g) probably related to the food available during the two seasons (627 vs. 97 kg DM/ha). It shows that the winter and autumn are the peak times for these animals in extensive systems for which a quantity supplementation is necessary. From a qualitative point of view, a protein deficiency is observed during the three seasons especially for fattening animals.