Effect of disodium fumarate on ruminal metabolism and rumen bacterial communities as revealed by denaturing gradient gel electrophoresis analysis of 16S ribosomal DNA

The aim of the present study was to examine the effects of feeding diets with addition of disodium fumarate (DF) to goats on ruminal metabolism and changes of rumen bacterial communities. Four cannulated goats were used in a 4 x 4 Latin square design. The results showed that ruminal pH increased linearly (P<0.01)as the amount of DF added increased, while lactate production decreased linearly (P<0.01). DF addition did not affect the production of acetate, propionate, butyrate, TVFA and NH3-N. The effect of DF on the changes in rumen bacterial-community structure of goats was analyzed using 16S rDNA-based approaches. Amplicons of the V6-V8 variable regions of bacterial 16S rDNA were analyzed by denaturing gradient gel electrophoresis (DGGE), cloning and sequencing. Differences in rumen bacterial community structure were determined based on the Shannon index of diversity for pairwise comparison of the DGGE fingerprints and revealed significant changes in rumen microbiota after DF addition. As compared with those fed with the control diet, goats fed on the diets with DF addition showed a higher bacterial diversity. The sequences of seven amplicons in total I I clones showed less than 97% similarity with those of previously identified or unidentified bacteria, suggesting that most bacteria in the gastrointestinal tract have not been cultured or identified. Amplicons related to Succinivibrio dextrinosolvens species were found in most DGGE fingerprints derived from goats on the diet containing DF, but not in goats on the control diet. These results demonstrated the ability of DF to improve the metabolism of rumen lactate fermentation and to influence the bacterial composition of the rumen in goats. (C) 2007 Elsevier B.V. All rights reserved.