Food costs in rainbow trout farms are about 50% of production costs (Barrows et al., 2007). Because of inattention of most aquaculturists in exact calculation of FCR and not using qualified food, sometimes food costs will rise a lot and won't be economical. The newest method for fish food production is production during the process of extrusion. Extrusion process is processing materials with high temperature in a short time (HTST) and is done by combined operation of humidity, heat, mechanical energy and pressure (Watanabe and Pongmaneerat, 1993)