ABSTRACT The overall goal of the present study is evaluating the performance of extrusion machine to produce a strong and durable cattle feed pellets with minimum cost using a partial replacement of rice straw in the standard cattle ration (control). Some operating parameters affecting the performance of machine were evaluated under different feeding rates of 100, 200, 300 and 400 kg/hr., two percentages of rice straw residue 12.5, 25% and control, three distances between die and screw (compression room) 1, 1.5 and 2 cm, three holes diameters 8, 11 and 14 mm using constant ration moisture content of 30% (wb) taking into consideration machine productivity, pellets quality, pelleting efficiency, energy requirements and total costs. From the obtained results, the extrusion machine could be operated with rice straw percentage of 12.5%, die hole diameter of 8 mm, screw-die distance of 2 cm and feeding rate of 400 kg/hr., to achieve the highest values of bulk density of 1.121 g/cm3, pellet durability of 90.70% and pelleting efficiency of 82.52% with machine productivity of 92.34 kg/hr., energy requirements of 269 kW.hr./Mg and pelleting total cost of 2394.90 LE/Mg. The results revealed that 12.5% replacement of rice straw in the standard ration with the previous parameters saved about 236.91 LE/Mg. Key words: Extruder, cattle pellets, rice straw, partial replacement, pellet quality, total cost