Abstract: A livestock feed mixer was designed, constructed and evaluated for its performance using mass of shelled corn as tracer. The machine was tested using a feed composed of 12.63 kg wheat bran, 12.63 kg wheat powder, 12.63 kg faba bean bran, 10.1 kg cotton cake, 1.18 kg of salt, 0.84 kg molasses and 2 kg ungrounded corn replicated thrice at four mixing durations of 5, 10, 15 and 20 minutes and paddle shaft speed of 480, and 580 rpm. The effectiveness of mixing was assessed on the basis of mass of shelled corn, and percent of coefficient of variation (CV %) and degree of mixing of sample collected at the end of each test. The best values of coefficient of variation (13.09 %) and degree of mixing (86.91 %) were obtained at mixing paddler shaft speed of 580 rpm and mixing time of 10 minutes. Hence, it can be concluded that the machine, the prototype livestock feed mixer, should be operated at speed of 580 rpm with maximum holding/mixing time of 10 in order to make the owning and operating of the machine productive (in terms of kg/hr) and economical (in terms labour and energy cost birr/kg of mixed quality feed. The capacity of the machine is about four quintals per hour or 32 quintals per day of 8 hours of work.