In order to increase the animal production such as meat, milk and wool, it is vital to relate information on the nutritional characteristics of feed available with the requirements for nutrients according to the purpose and rate of productivity of the animals in question. In the industrialised countries, this information has been incorporated in tables of “Feeding Standards” which interpret chemical analyses of feed resources in terms of their capacity to supply the energy, protein, vitamins and minerals required for the particular productive purpose. However, in Iran,due to the lack of such tables, researchers have had no alternative but to use the mentioned “Feeding Standards” tables for their research work. This had led to little improvement in animal production in Iran since the tables mentioned have been made to meet the Industrialised countries conditions such as resources and environment. Additionally, in Iran where low-quality roughages are the main component of the ruminants diet, it is essential that feed evaluation systems are developed to take this into account. An example of this, although urea/ammonia treatment has been adopted in some areas, there is no up-to-dated methods to investigate by how much nutritive value is increased. Therefore, the nutritive value of some selected Iranian feedstuffs, barley grain (BG), alfalfa (AA), wheat straw (WS), ammoniated wheat straw (TWS) was assessed by chemical analysis, digestion and degradation studies.