Abstract: Three goats fitted with cannula, were used to provide rumen liquor to investigate the effects of limiting amino acids on rumen fermentation and microbial community in vitro. The removel method was used in current experiments. Treatments: Total essential amino acid (TEAA), His-removel, Lys-removel, Met-removel, branch chain amino acid (BCAA)-removel. Results showed that, the pH-value ranged between 5.9 and 6.8, with the highest mean value was observed for the group with BCAA-removel (6.54) in the culture. Concentration of NH3-N ranged between 10.99 to 30.51mg/100ml, with the group of TEAA recorded the highest average NH3-N concentration (17.85mg/100ml). Yields of microbial protein and limiting degree on microbial growth were varied with treatments, and lowest accrued in treatment with BCAA-removel (0.1389 mg/ml, 0.1772mg/ml and 0.3161mg/ml for bacteria, protozoa, and mixed microbes) (P<0.01) respectively, compared to the group with TEAA, microbial production of mixed microbes decreased by 44.52%. As for micro-flora, the protozoa to bacteria ratio was lowest for the group with Lys-removel (89.12%), while highest for the group with BCAA-removel (127.60%) (P<0.01). Furthermore, PCR - SSCP analysis revealed that, microbial profile subjected to the substrates within bacteria and protozoa group. It was therefore concluded that dietary amino acid influenced both fermentation and microbial characteristics.

Key words: limiting amino acids, Rumen microbes, Limiting degree, PCR - SSCP