Artificial slurry (4% dry matter) was prepared using fresh feces and urine obtained from four pregnant sows fed with commercial diet. Freeze-dried dairy cattle feces were used (external archaea) as co-inoculum (Co-i) and structural carbohydrates (CHO: apple pulp; sugar beet pulp; and wheat straw) as substrates. Bottles were incubated (39 ± 1°C for 56 days), and the gas production was measured (mbar) and converted to the volume. A sample of produced gas was taken and analyzed for methane concentration using a gas chromatography. Bottles were opened at days 0, 25, and 56 to determine total bacteria, total, and hydrogenotrophic methanogens archaea (HMA) concentrations using quantitative polymerase chain reaction and population biodiversity using denaturing gradient gel electrophoresis (DGGE). Incubation time reduced the titers of total bacteria and archaea (P