Effects of two sources of tannins (Quercus L. and Vaccinium vitis idaea L.) on rumen microbial fermentation: an in vitro study

The aim of the experiment was to determine the effect of different sources of tannins on the in vitro rumen fermentation with focus on methane production. In the experiment, a rumen simulation system (RUSITEC) equipped with 4 fermenters (1 L) was used in three replicated runs (6 d of adaptation and 4 d of sampling) to study the effects of Quercus cortex extract (QC), Vaccinium vitis idaea (VVI) dried leaf extract and a mixture of VVI/QC on rumen microbial fermentation. Fermenters were fed 10.9 g/d of dry matter (DM) of a 600:400 forage:concentrate diet. Treatments were control, QC (2.725 mL), VVI leaves 0.080 g) and mixture of QC/VVI (1.362 mL+0.040 g) and were randomly assigned to fermenters within periods. The equivalent of 2.5 g of tannins/kg dietary DM from three sources of tannins was evaluated. All tannin sources decreased CH4 and ammonia concentrations, as well as protozoa and methanogen counts (P<0.001). Vaccinium vitis idaea and QC/VVI tended (P=0.005) to reduce the acetate to propionate ratio. There were no changes in nutrient digestion. Results suggest that these sources of tannins, especially VVI have the potential to reduce rumen CH4 production and ammonia concentration without negative effects on In vitro DM digestibility, total volatile fatty acids and pH.