Tannins from different plants in the rumen of ruminants have different effects on the extent and rate of protein degradation and thus also on the efficiency of protein or nitrogen utilization. The purpose of this study is to examine how the treatment of RSM with different types and concentrations of tannins affects the kinetics of fermentation and VFA synthesis, and how different drying temperatures of the mixture of RSM with water and tannins affect this. We expected that higher concentrations of tannins and higher drying temperatures would reduce gas production and reduce VFA synthesis. We performed an in vitro laboratory experiment, in the first part of which we determined in vitro gas production, and in the second part, VFA production. We treated RSM (100 g) with three concentrations (0, 50, and 100 g/kg DM) of sweet chestnut (Castanea sativa) and quebracho (Schinopsis spp.) water extract in 250 ml of distilled water for 24 hours, and then dried them in a drying oven at 50 ºC and 80 ºC and by freeze-drying. We performed an in vitro analysis of gas production using the ANKOM RF gas production system. We found that the indicators of fermentation gas production kinetics are influenced by the interaction between tannin concentration and drying temperature, while the total and individual VFA are also influenced by the type of tannin and drying temperature. We conclude that for both types of tannins, the reduction in gas production and VFA are achieved with a higher tannin concentration (100 g/kg DM) and a drying temperature of 80 ºC. Studying these and other methods for reducing gas production would help in the development of comprehensive strategies for improving the supply of metabolizable protein to ruminants.
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