OBJECTIVE: To investigate the use of cassava stems as an alternative feedstuff for ruminants, a study was conducted measuring the effect of replacing rice straw with untreated and treated dried cassava stems. The study assessed its impact on feed intake, nutrient digestibility, blood metabolites, and the growth performance of Thai native cattle. METHODS: Six male cattle were arranged in a 3×3 replicated Latin square design to receive three treatments. All animals were provided with rice straw ad libitum and 14% crude protein (CP) concentrate at 0.5% body weight. Treatment variations consisted of a control group (Ctrl), one group that replaced rice straw with dried cassava stem (DCS), and another group that replaced rice straw with alkali, urea, and Ca(OH)2, treated dried cassava stem (tDCS) at 15% of rice straw intake. The experiment spanned three 21-day periods. RESULTS: Feed intake, body weight gain, and feed conversion ratio (FCR) were similar across treatments. Total tract apparent digestibility for the cattle, which included dry matter, organic matter, CP, neutral detergent fiber, and acid detergent fiber, was higher than those on the tDCS treatment compared to the other groups (p<
0.05). Ruminal pH, volatile fatty acid concentration, and blood metabolites remained unaffected by dietary treatments, except for BUN which was increased with tDCS replaced rice straw (p<
0.05). Alkali-tDCS helped reduce rectum temperature compared to the control and DCS group (p<
0.05). CONCLUSION: Replacing rice straw with tDCS improved nutrient digestibility but did not significantly impact feed intake, growth rate, FCR, rumen fermentation, and the blood metabolite of Thai native cattle.