During the last decade, development of the buffalo industry has been undertaken in Iran. The prospects for beef production from buffalo management have shown to be successful under local environments. Buffaloes reared under feedlot conditions with suitable diets have the potential to produce high quality carcass (Udeybir and Mandal, 2001). In terms of nutrition, studies are needed for the validation of nutrient requirements (especially protein and energy) for different physiological stages. A system to monitor the nutritional status of buffaloes would be beneficial to reduce losses and maximize efficiency of nutrient utilization. To optimise protein efficiency and reduce nitrogen wastage, diets need to be formulated to provide optimum nitrogen concentration for maximum rumen microbial yield and growth. However, limited work has been reported on nutrient requirements of growing and fattening buffalo calves. The objective of this work was to study the response of Iranian buffalo male calves to the different levels of energy and protein in the diet from 12 to 18 months of age.