The Cornell Net Carbohydrate and Protein System (CNCPS) model has recently been increasingly employed in preparation of balanced feed ration of dairy cattle in Iran. However, a lack of appropriate characterization of the feeds has restricted the model's application. This study was conducted to evaluate the protein contents of some feedstuffs (wheat bran, sugar beet pulp, soybean meal, cottonseed meal, cottonseed whole, corn gluten meal, poultry offal meal, blood meal, canola meal and bagasse) commonly used in the cattle ration in Iran with characteristics needed as inputs for CNCPS. Based on data obtained from this work, the level of neutral detergent fibre, ether extract, crude protein, soluble protein, non protein nitrogen, soluble true protein, neutral detergent insoluble protein and acid detergent insoluble protein contents were numerically different from the records of CNCPS, the difference for which may be due to climate, agricultural practices, and storage conditions. Hence, the use of date obtained for the available feeds in place of CNCPS' tabular values is strongly recommended in formulating balanced rations. This would expectedly result in more efficient use and less waste of nutrients.