Firmicutes and Bacteroidetes are closely related to body fat in humans and mice, which are the two dominant bacterial divisions of gut microbiota in mammals. Here real-time PCR analysis indicated that Meishan pigs had a 34% reduction in percentage Bacteroidetes (P = 0.008) and a significantly lower proportion of Bacteroides (P = 0.013) than Landrace pigs. The percentage of Bacteroidetes or Bacteroides had a negative correlation with body fat (R2 was 0.63 for Bacteroidetes and 0.57 for Bacteroides, P < 0.05). There was a trend that the percentage of Firmicutes in Meishan pigs was higher in numerical value than in Landrace pigs, although this difference was not statistically significant (P = 0.290) between the two breeds. These suggested that body fat correlated with the percentage of Bacteroidetes division of the gut microbiota in the common pig breeds, and the differences of gut microbial ecology in obese versus lean animals may be analogous.