The change in regeneration pathway of plants by seeds or soil seed bank dynamics is one of the most important impacts of herbivores in grazing ecosystems with long history of grazing. However, this role of herbivores and its importance for the dynamics and composition of the vegetation is often neglected. Herbivores consume seeds of many plant species and disperse them within and among sites where they graze. This is in particular very important in highly-degraded ecosystems with no proper seed reserve in the soil; so that the natural regeneration of the vegetation relies on the seed dispersal of target species from the distant seed sources. To assess the potential seed dispersal of semi-steppe rangeland plant species by domestic herbivores, various degradation levels of rangelands in the central Zagros region (moderate to good rangelands, degraded rangelands and ploughed ones or old rainfed sites) were considered. 12 different rangeland sites (each at least 1000 m 2 ) including 4 replicates with homogeneous vegetation were selected for each of the three degradation levels. In each site, vegetation (cover, relative frequency and flowering pattern of plant species) was studied using ten 1m2 plots systematically located along two 100 meter transects (10 meter apart from each other). For each site, a pooled dung sample of 10 freshly pellet groups of domestic herbivores was collected in four different periods (June, July, August and September) during grazing season (in total, 48 pooled dung samples). Dung samples were dried in a dark room by exposing to open air and then from each a 150 gram sample was taken and kept for two months in the refrigerator at 3c for cold stratification treatment. Seed content of dung samples then was assessed in a greenhouse germination experiment over a period of six months. In total, 2039 seedlings from 50 different species, 16 families and 52 plant genuses were germinated from dung samples. Seed content of dung samples was mostly composed with palatable herbaceous species with no dispersal mechanism or adaptation except the production of many small seeds. The highest and the lowest dung seed densities were observed in July and June, respectively. At the beginning of grazing season, seed content of dung samples was composed with palatable annual forb species while it was composed with less or unpalatable perennial species towards the end of season. Seed species composition of dung samples was clearly different from plant species composition of the vegetation plots where they had been dropped, but it was more similar to plant species composition of vegetation plots studied in the moderate to good rangeland sites. Moreover, the highest dung seed density was observed in the dung samples collected from degraded and ploughed rangelands. These findings together suggest a likely transfer of seeds of plant species from moderate to good rangeland to the other sites in different degradation levels. As most of the plant species recorded in the vegetation plots regenerate by seed, seed dispersal by this vector may have significant role in natural regeneration of the vegetation, only if other environmental and management factors met. Results of this study, as the first one in the country, increase our knowledge about seed dispersal of range plant species and can be applied for regeneration and protection of the vegetation in the semi-steppe grazing ecosystems. Keywords: Central Zagros region, dung samples, grazing ecosystems, seed germination experiments, semi-steppe rangelands, soil seed bank dynamics, vegetation natural regeneration.