The objective of this study was to investigate effects of cereal type and steam-flaking processing on nutritive values of maize, wheat and rice (with whole hulls). Intact and steam-flaked grains of maize, wheat and rice were measured for in situ degradability using nylon bag method and predicted for protein digested in the small intestine (PDI) using the method of French Protein System. Data obtained were subjected to ANOVA as a 2 × 3 factorial design with 3 replicates by the GLM procedure of SAS (Version 9.0; SAS Institute, Carry), and a Duncan significant difference test was used to determine the differences among means. Significance was declared at P ≤ 0.05. Three ruminally cannulated Limousin steers averaging 400kg of body weight were used. Steers were fed a TMR diet twice daily. The results showed that the rumen effective degradation rate of dry matter (DM), organic matter (OM), starch and crude protein (CP) of the grains were: wheat (80.91%, 81.34%, 87.68% and 81.34%) > rice (71.10%, 72.84%, 84.79% and 72.84%) > maize (65.80%, 63.99%, 74.60% and 63.99%). The rumen degradation rate from fast to slow were: rice > wheat > maize. DM, OM, Starch and CP effective degradability of rice were increased by steam-flaking (SF) processing. SF processing also increased DM, OM, Starch and CP degradation rates of maize and wheat. However, DM, OM, Starch and CP degradation rates of rice were decreased by SF processing. Rumen nondegradable nitrogen from feed (PDIA) and PDI of wheat (50.07 and 99.97g/kg DM) were significantly higher (P < 0.01) than maize (34.83 and 55.03 g/kg DM) and rice (23.16 and 46.27 g/kg DM). PDI of maize was reduced (P < 0.01) by SF processing, while no significant differences were observed between PDI values of intact and steam-flaked wheat or rice. In summary, rumen effective degradation rate and PDI of wheat are higher than maize and rice. Steam-flaking can significantly improve the rumen effective degradability of rice and decrease the PDI value of maize, but have no significant effect on PDI values of wheat or rice.