Evaluation of the effects of tropical tanniferous plants on rumen microbiota using qRT PCR and DGGE analysis

Tanniferous forages may have bacteriostatic and/or bactericidal effect on different rumen microbial populations. We investigated the influence of the tropical tanniferous plants Styzolobium aterrimum (STA), Styzolobium deeringianum (STD), Leucaena leucocephala (LEU), and Mimosa caesalpiniaefolia (MIC) containing 20, 64, 56, and 105 g condensed tannis (CT)/kg dry matter (DM) and Cynodon spp. cv. Tifton 85 (CYN) as control on Fibrobacter succinogenes and methanogenic microbes in rumen liquor from sheep using the in vitro gas production technique (Hohenheim gas test). The relative gene expression of F. succinogenes at t1/2 (time point when 50% of the maximal gas production has been reached) analyzed by quantitative PCR was 0.20- and 0.28- fold lower than the control when LEU and STA was applied and 0.91- and 0.85-fold lower with MIC and STD. Methanogenic population was 0.29- and 0.58- fold reduced with STA and LEU compared to the control, but 5.50- and 1.43- fold higher with MIC and STD. At 24 h, F. succinogenes was reduced for all legumes as well as methanogenic bacteria, except for MIC which increased 4.15-fold. Denaturing gradient gel electrophoresis (DGGE) of the methanogenic community resulted in different band patterns: CYN presented some strong bands, which became weaker in the analyzed treatments. Some bands appeared weaker, especially in MIC and STD, but not in STA and LEU. MIC seemed to increase the total number of weak bands. Overall, the tannin-rich plants negatively affected the F. succinogenes population and caused changes in the structure of the methanogenic community.