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Abstract A Fish feed mixing machine was designed, developed and the effect of speed and retention time on the performance of the mixer was evaluated. The mixing system was tested using three fish feed ingredients; bone meal, groundnut cake and maize grain which was purchased from the market in Akure, Ondo State, Nigeria. The moisture content of the bought ingredients was determined to be 13.1%, 14.7% and 17.5% moisture content dry basis respectively. The mixer was tested using a feed component of three equal measures of 10 kg of ground corn (maize), milled groundnut cake and bone meal which were initially retained on 2 mm, 850 µm and 150 µm sieve respectively. The experiment was replicated thrice at four retention time (5 min, 10 min, 15 min and 20 min) and five mixer screw speed (100 rpm, 150 rpm, 200 rpm, 250 rpm and 300 rpm).Regression analysis was carried out on the data collated during the evaluation of the mixer, the analysis was used to develop models which is capable of predicting the electrical energy (kJ) consumed, degree of mixing (%) and average power (kW) consumed during mixing.An average CV of 4.04% was obtained at 200 rpm in 20 minutes retention time while 356.4 kJ electrical energy was consumed, this shows a significant reduction of non-uniformity in feed components for the samples tested. The degree of mixing attained was 95.96% which portrays an improvement of about 0.2% reduction in non-uniformity of components among samples when the mixing duration was 20 min at 150 rpm. The average power and electrical energy consumed during mixing was observed to be significantly dependent on the retention time while speed does not have a significant effect on the average power and energy consumed during mixing, the degree of mixing increases as the retention time increases. There is a decrease in energy consumed as the speed increases under a constant retention time while the energy consumed increases as the retention time increases with a constant speed.Key Words – Bone Meal, Groundnut Cake, Ground Corn, Mixing Machine, Degree of Mixing, Coefficient of Variation
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