摘要：Objective: This study investigated in vitro characteristics of fermentation of fattening rations with different protein-energy levels fed to male Bali cattle. Methodology: Rations were composed of grass, Gliricidia sepium , corn meal and rice bran with different proportions of protein and energy. Ration T1 was standard protein-standard energy/SS [(12.06% Crude Protein (CP) and 62.66% Total Digestible Nutrients (TDN)], T2 was standard protein-high energy/SH (10.14% CP and 65. 66% TDN), T3 was high protein-standard energy/HS (14.79% CP and 63.66% TDN) and T4 was high protein-high energy/HH (13% CP and 67.48% TDN). Data were analyzed by one-way analysis of variance. Results: Although, pH level of rumen fluid was similar for all treatments (p>0.05), digestibility of dry matter and organic matter in rations T4 and T3 was higher (p<0.01) than that for T1 and T2. For N-NH3 (mg/100 mL), the yield of T4 and T3 was higher (p<0.01) than that for T1 and T2. Meanwhile, total VFA, acetic and propionic acids in T2, T3 and T4 were higher (p<0.01) than for T1 but butyric acid levels for T4 were higher (p<0.01) than that for T1, T2 and T3 and the acetic: propionic acid ratio of T4 was lower (p<0.01) than that for T1, T2 and T3. Microbial protein synthesis (mg mL1) for the T1 ration was higher (p<0.01) than that of T2, T3 and T4. Conclusion: Varying the protein and energy levels of rations fed to male Bali cattle did not affect rumen pH but the digestibility of dry matter and organic matter was unclear. Moreover, N-NH3 utilization and VFA yield were not optimal for protein biosynthesis by microbes.
