The present invention relates to the use of smart additive to improve the utilization of poultry and fish low protein diets. The smart additive consists of three factors ; natural antioxidants, acidify agent and sulfate (as transfer material ). Smart additive use with inclusion rate from 9 to 11 kg / ton feed to improve the utilization of poultry and fish low protein diets which contain 15 to 20 % below standard protein requirements levels