Field crop residues are considered among the most variable and important materials in Egypt. The research work conducted at private milking animal farm in Shobak Basta village Zagazig city, Sharkia Governorate to accomplish the machine field work before and after modification. The aim of the present work is to introduce a simple chopper for animal feed suitable for the small holder farm. Also, to measure and calculate the performance, productivity and operational costs. The machine modification was introduced to improve the chopping of rice straw process and increase machine productivity, which was necessary upon field test. The machine modified and manufactured from local materials at a private sector workshop. Results of this study could be summarized in the following points: 1- The maximum productivity reached 2.85 kg/min. using two knives, at 4 mm knives clearance, 18.7 m/s cutting drum speed and 16 % rice straw moisture content 2- Using two knives on the cutting drum increased machine productivity than using three or four knives. 3- Cutting efficiency and quality increased by decreasing the clearance and straw moisture content. Meanwhile, cutting length was positive with the clearance. 4- Cutting one ton using the machine costs 23 LE. Meanwhile cutting one ton of rice straw by labor at the same conditions costs 400 LE.