Effect of slurry dilution, structural carbohydrates, and exogenous archaea supply on in vitro anaerobe fermentation and methanogens population of swine slurry

Abstract

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 degrees 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<0.01) but did not modify HMA population. Doses of Co-i showed a positive correlation with HMA titers, although interacted with an incubation period (P<0.001); at 5% Co-inoculation, total bacteria decreased significantly (0-25 days) but remained steady until day 56 (P>0.05), whereas at 10% Co inoculation, titers decreased constantly. Most of the archaeal DGGE bands were observed in all samples, suggesting a common microbial population origin but Co-i supply altered the DGGE structure of archaea populations

This work was supported by the Ministry of Economy and Competitiveness of Spain and the European Union Regional Development Funds (AGL2010-20820). Ahmad Reza Seradj is a recipient of grant from the Government of Catalunya (FI-DGR 2011) and Henris Morazan was a recipient of grant from MAEC-AECID 2009–2011.