Investigating the effects of supplementing dairy cows diet with condensed tannin of chestnut supplement (Silvafeed) on rumen fermentation, nutrient digestibility and microbial enzyme activity in vitro

This study was conducted to investigate the effects of supplementing dairy cows diet with various levels of commercial chestnut condensed tannins (CT) supplement (Silvafeed), on in vitro gas production (GP) and fermentation parameters, nutrients digestibility and activity of rumen microbial enzymes in vitro using rumen liquor of cow. Dietary treatments were control diet (without CT) and supplementing control diet with CT at the levels of 0.45, 0.90 and 1.35 g per kg dietary dry matter (DM). Inclusion levels of dietary tannins were based on recommendation of manufacturer. Results showed that GP at all of incubation times, potential (b) and rate (c) of GP were not affected by experimental treatments (P>0.05). Except for ammonia nitrogen concentration and microbial protein production which were decreased and increased with increasing rate of CT in the diet respectively (P<0.05), while the other fermentation parameters were unchanged by incubation of experimental diets (P>0.05). Activity of fibrolytic enzymes such a carboxymethyl cellulase, microcrystalline cellulase and filter paper-degrading activity were not affected by supplementing diet with CT (P>0.05), while rumen protease activity was decreased linearly with enhancing level of CT in the diet (P<0.05). In conclusion, the results of present study revealed that adding condensed tannins to dairy cows diet up to 1.35 g/kg dietary DM improved nitrogen metabolism in the rumen, and this could reduce the requirements for dietary rumen undegradable protein.