Abstract: The objectives of this study was to evaluate the influence supplementation levels of Yeast-Malate Fermented Cassava Pulp (YMFCP) replace soybean meal in concentrate on feed-intake, Average Dairy Gain (ADG), rumen ecology and blood metabolites in crossbred native cattle. Five, two years of female crossbred native cattles weighing at 250±10 kg were randomly assigned according to a 5 x 5 Latin square design. The dietary treatments were as follows: T1 = supplementation of YMFCP replace soybean ratio at 0:100%; T2 = supplementation of YMFCP replace soybean ratio at 25:75%; T3 = supplementation of YMFCP replace soybean ratio at 50:50%; T4 = supplementation of YMFCP replace soybean ratio at 75:25%, T5 = supplementation of YMFCP replace soybean ratio at 100:0%, respectively. The cows were offered the treatment concentrate at 1.0%BW. All cows were fed ad libitum of rice straw with water and a mineral salt block. The results have revealed that rumen fermentation, blood metabolites and average daily gain were significantly different for all treatments. The populations of protozoa and fungal zoospores were significantly different as affected by supplementation levels of Yeast-Malate Fermented Cassava Pulp (YMFCP) replace soybean meal in concentrate. Moreover, supplementation levels of Yeast-Malate Fermented Cassava Pulp (YMFCP) replace soybean meal ratio at 50:50% in concentrate with rice straw as roughage source could highest improved ruminal fermentation efficiency, average daily gain including increase populations of bacteria and fungi zoospores, but decreased protozoal populations in rumen of crossbred native cattle.