The caecal chyme of pigs was incubated anaerobically in McDougall buffer with and without fumonisin B1 (5 μg/ml) for 0, 24 and 48 h. The plate count agar technique was applied for enumerating the amount of bacteria including aerobic, anaerobic bacteria, coliform, Escherichia coli and Lactobacillus sp. The quantitative polymerase chain reaction was also performed to estimate the number of copies of the total bacteria, Lactobacillus, Bacteroides and Prevotella. No significant differences in the amount of bacterial groups between the experimental (buffer, chyme, and fumonisin B1) and control 1 groups (buffer + chyme) were observed in both methods. Fumonisin B1 and hydrolysed fumonisin B1 concentration were analysed by liquid chromatograghy - mass spectrometry. There was no significant difference in FB1 concentration between the experimental and the control 2 group (buffer and fumonisin B1) at 0 h incubation, 5.185 ± 0.174 μg/ml compared with 6.433 ± 0.076 μg/ml. Fumonisin B1 concentration in the experimental group was reduced to 4.080 ± 0.065 μg/ml at 24 h and to 2.747 ± 0.548 μg/ml at 48 h incubation and was significantly less than that of in the control group. Hydrolysed fumonisin B1 was detected after 24 h incubation (0.012 ± 0 μg/ml). At 48 h incubation time, hydrolysed fumonisin B1 concentration was doubled to 0.024 ± 0.004 μg/ml. These results indicate that fumonisin B1 can be metabolised by caecal microbiota in pigs though the number of studied bacteria did not change.