Abstract: In vitro fermentation characteristics of different fiber substrates by faecal microbiota and fiber-degrading baceria in faeces from Meishan and Landrace sows were compared. Fresh faeces from Meishan and Landrace sows were collected and used as inoculum in an in vitro fermentation test. Eight different substrates, (pectin, cellulose, xylan, inilin, wheat hul, wheat bran, maize pulp, and alfalfa) were used in the test. After 96 h fermentation, gas production was recorded, and gas samples collected to determine VFA concentrations. Total bacterial DNA was extracted and used for DGGE and real-time PCR to analyse microbiota composition and the main fiber-degrading bacteria. Cumulative gas production, concentration of acetate and of total VFAs were significantly higher (P<0.05) when the faeces from Landrace sows were used as inoculum as compared with those from Meishan sows. There was no significant (P>0.05) difference in the concentrations of propionate and butyrate between the two breeds. T_1/2 and T_max were significantly lower (P<0.05) in Landrace sows than in Meishan sows. The order of degradability of all substrates was: inulin>wheat bran>pectin>alfafa>wheat hull>maize pulp>xylan>cellulose. DGGE anlysis of total bacterial communities showed that there were no pig breed specific bands in the profiles from the faeces of the two breeds. Real-time PCR analysis showed that the 16S rRNA gene copies of total bacteria in faeces of Meishan sows were significantly (P<0.05) higher than those in Landrace sows, while there was no significant (P>0.05) difference in the 16S rRNA gene copies of Bacteroidetes, Fibrobacter succinogenes, Ruminococcus flavefaciens and Ruminococcus albus and their proportions within the total bacterial population. Although there was no significant difference in the numbers of main fiber-degrading bacteria between Meishan and Landrace sows, the Landrace sows may have a stronger ability to degrade fiber as compared to Meishan sows.