Ruminal Manipulation to Modify Toxic Compounds in Leguminous Trees
Investigators (most current known information)
It is possible to alleviate the anti-nutritional effects of leguminous trees by modification of the rumen microbial population by isolating, culturing and reintroducing microorganisms, capable of transforming anti-nutritional compounds, into susceptible ruminants. In this study two approaches were followed to attain this goal. The first involved isolating and characterizing rumen organisms capable of modifying known anti-nutritional factors. The second approach was to identify anti-nutritional factors in plants that have potential as fodder trees in arid regions. A hypotheses we tested while isolating organisms is that microorganisms from ruminants adapted to diets containing leguminous fodder trees are able to modify or degrade potential anti-nutritional factors better than rumen populations from animals fed conventional roughage diets.
Metabolic transformation of three classes of anti-nutritional factors, mimosine (non-protein amino acid); tyramine (aromatic amine) and ferulic acid (phenolic monomer) by rumen inocula indicated that there was no difference in rate or extent of modification, whether the animals were fed legume-supplemented diets (Leucaena, Sesbania and Acacia spp.) or conventional roughage diets. Bacteria, protozoa and/or the bacteria intimately associated with them, but no fungi were able to modify tyramine. Bacteria capable of modifying p-coumaric acid, gallic acid and hesperidin were isolated from enrichment cultures. Phylogenetic studies indicated that organisms capable of modifying phenolic monomers are related to Butyrivibrio fibrisolvens.
The results indicate that organisms capable of modifying anti-nutritional factors were present in rumen populations in both Africa and North America and it was possible to isolate cultures, which may be useful in developing rumen inocula. Acacia angustissima was identified as a tropical legume with potential as a fodder tree. However, A. angustissima has been shown to be highly toxic to sheep. A rat bioassay was developed to evaluate A. angustissima and to identify the anti-nutritional factor(s) present. A. angustissima fed at 10, 15 and 20% of the rodent diet caused severe weight loss and early death (2-7 days) in weanling rats. In an experiment comparing A. angustissima and Medicago sativa (alfalfa) as 7.5% of the rodent diet it was shown that anti-nutritional factors in A. angustissima caused decreased intake, resulting in weight loss. Extraction of plant material with various solvents indicated that the anti-nutritional facto(s) were present in fractions that were high in phenolics. Intake and average daily gain were significantly reduced if diets were fed containing more than 1% phenolics. An experiment is being conducted to determine whether the anti-nutritional effect of A. angustissima is due solely to the phenolics present or whether there is a synergistic effect between the phenolics and other unidentified compounds. DNA collected from cecal samples will also be analyzed with molecular methods to assess antimicrobial effects of the phenolics present. In vitro incubations of the phenolic-containing plant extracts with previously isolated and characterized bacteria may identify organisms capable of detoxifying the anti-nutritional factors of A. angustissima.
Articles in Journals
Smith, A.H., E.G. Zoetendal and R.I. Mackie. 2005. "Bacterial mechanisms to overcome inhibitory effects of dietary tannins." Microbial Ecology (in press).
Smith, A.H., M.Y. Mori, F.E. Kandil, C. Knight, D.S. Seigler and R.I. Mackie. 2004. "Anti-nutritional and anti-microbial proanthocyanidins from the forage legume Acacia angustissima." J. Chem. Ecology (in preparation).
Smith, A.H. and R.I. Mackie. 2004. "Effects of condensed tannins from Acacia angustissima on the ecology and diversity of tannin tolerant bacteria in rat feces." Appl. Environ. Microbiology 70:1104-1115.
Smith, A.H., J.A. Imlay and R.I. Mackie. 2003. "Increasing the oxidative stress response allows Escherichia coli to overcome inhibitory effects of Acacia mearnsii (wattle) tannins." Appl. Environ. Microbiology 69:3406-3411.
Smith, A.H., M.A. Wallig and R.I. Mackie. 2002. "Amelioration of the toxic effects of Acacia angustissima in rats with polyethylene glycol." Anim. Feed Sci. Technology 106:165-174.
Smith, A.H., A.A. Odenyo, P.O. Osuiji, M.A. Wallig, F.E. Kandil, D.S. Siegler and R.I. Mackie. 2001. "Evaluation of toxicity of Acacia angustissima in a rat bioassay." Anim. Feed Sci. Technology 91:41-57.
Zoetendal, E.G., A.H. Smith, M.A, Sundset, D.H. Akan and R.I. Mackie. 2004. "Characterization of the mechanisms of tannin resistance in Escherichia coli by transcriptional analysis." Presented, Annual meeting of the American Society of Microbiology, May. Orleans LA.
Zoetendal, E.G., A.H. Smith, M.A. Sundset, D.H. Akan and R.I. Mackie. 2003. "Mechanisms of tannin resistance in Escherichia coli: A DNA microarray approach." Presented, VI International symposium in the nutrition of herbivores, October. Merida, Mexico.
Smith, A.H., E.G. Zoetendal, M.A. Sundset and R.I. Mackie. 2003. "Application of molecular microbial ecology and functional genomics tools to elucidate mechanisms of tannin resistance in intestinal bacteria." Presented, FAO/IAEA international symposium on applications of gene-based technologies for improving animal production and health in developing countries. Book of extended synopses IAEA-CN-110,72, October. Vienna, Austria.
Smith, A.H. and R.I. Mackie. 2002. "Effects of condensed tannins from Acacia angustissima on the ecology of tannin tolerant bacteria in rat feces." Presented, RRI-INRA 3rd joint symposium "Beyond antimicrobials - The future of gut microbiology," June. Aberdeen, Scotland.
Smith, A.H. and R.I. Mackie. 2000. "Effect of Acacia angustissima on bacterial diversity in the rat cecum." In Proceeding of the 25th Biennial Conference on Rumen Function, 44.
Smith, A.H., Odenyo, A.A., Osuji, P.O., Wallig, M.A. and R.I. Mackie. 1999. "Evaluation of palatability and toxicity of Acacia angustissima using a rat bioassay." Presented, Satellite symposium polyphenolics in tropical ruminant production, IX ISRP. October. Matopos, Zimbabwe.
Smith, A.H., R. Aminov and R.I. Mackie. 1999. "Isolation, identification and phylogenetic placement of rumen bacteria capable of degrading phenolic monomers." Presented, XI international symposium ruminant physiology, October. Pretoria, South Africa.
Smith, A.H., A.A. Odenyo, P.O. Osuji and R.I. Mackie. 1997. "Biotransformation of anti-nutritional factors by rumen microbiota." Presented, 24th Biennial Conference on Rumen Function 24:24.
Smith, A.H., A.A. Odenyo, P.O. Osuji and R.I. Mackie. 1998. "Biotransformation of anti-nutritional factors by rumen microbiota." Presented, Eighth international symposium on microbial ecology, ISME 8:305.
Smith, A.H. 2002. The effect of tannins on bacteria in the gastrointestinal tract. Ph.D. Thesis, The University of Illinois at Urbana-Champaign. Urbana IL.