The first experiment was conducted to examine the optimum level of cassava mixed with GML (Glutamic Mother Liquid) at varied ratio (2:1, 2.5:1, 3:1 and 3.5:1). Sixteen White Lumpun cattle aged 2 years old of about 136 kg body weight were fed on 60 % concentrate and 40 % rice straw based on dry matter of 2.8 % BW. It can be concluded that ground cassava chip and Glutamic Mother Liquid was 3.5:1 (Called cassavi 3.5) as percentage of salt was lower and the amouth of concentrate intake (% BW

P< 0.05) and total feed intake were higher than (P > 0.05) the other groups. The objective of the second experiment was to study the effect of various level of maize substitued with cassavi 3.5 (0, 50, 75 and 100% on animal performance. Average daily gain of 50 % cassavi 3.5 was the highest (P < 0.05). Cost per gain (P < 0.01) tended to be depressed when cassavi 3.5 was increased. Feed intake and cost per gain were higher in animal aged more than 2.5 years old compared to animal age less than 2.5 years. (P < 0.05). The third experiment involved comparison of average weight of each detailed cut. This experiment was concluded that percentage of chuck, rib, brisket, plate, round, loin, flank and kidney fat of each treatment was not different. But percentage of fore shank was different (P < 0.05). The percentage of them were similar (P > 0.05) between different aged-group.