BACKGROUND: Tannins added to animal diets may have a positive effect on energy and protein utilisation in the rumen. The objective of this study was to examine the impact of different sources and concentrations (20, 50, 100, 150 and 200 g kg−1 dry matter (DM)) of condensed (acacia and quebracho) and hydrolysable (chestnut and valonea) tannins on rumen microbial fermentation in vitro. The experiment also included a negative control with no tannins (control) and a positive control with monensin (10 mg L−1).
RESULTS: In vitro gas production and total volatile fatty acid (VFA) concentration decreased as tannin concentration increased. Addition of acacia, chestnut or valonea tannins at ≥ 50 g kg−1 or quebracho tannins at ≥ 100 g kg−1 resulted in a decrease (up to 40%) in methane (CH4) production compared with the control. Valonea tannins were the only tannin source that reduced (−11%) CH4 production at 50 g kg−1 without affecting VFA concentration. Tannin treatments reduced ammonia (NH3) and branched-chain VFA concentrations, indicating a reduction in ruminal protein degradation. Monensin reduced CH4 production (−37%) and NH3 concentration (−20%) without affecting total VFA concentration.
CONCLUSION: Supplying acacia, chestnut or valonea tannins at 50 g kg−1 has the potential to reduce CH4 production and ruminal protein degradation with minimum detrimental effects on efficiency of ruminal fermentation. Copyright © 2012 Crown in the right of Canada. Published by John Wiley & Sons, Ltd