Levels of digestibility and protein content necessary for maintenance, weight gain and lactation were estimated for Saiga antelope (Saiga tatarica). Estimates were based on results of digestionbalance trials using confined animals, and feeding trials involving tractable animals at pasture. Threshold parameters were estimated by regression of metabolizable energy intake and body weight gain, food digestibility and metabolic energy intake, protein content in food and the amount of consumed digestible protein. To meet maintenance requirements, food digestibility must be ³ 59%, with protein content ³ 7.7%. To meet requirements for growth and lactation, minimum digestibility must be 6168%, with protein content ³ 14%. When feeding on native semi-desert range, free-ranging Saiga antelope can meet these nutritional thresholds only through selective foraging. Therefore, when evaluating grazing capacity of Saiga habitat it is important to take into consideration that only a small portion of the total plant biomass is comprised of plants and plant parts of sufficient quality.