The effects oftannin from tea residueon the nutrient intake, milk yield, feed utilization efficiency, and the level and intensityof methane emissions (CH4) of lactatingdairy cows were investigatedin two experimental periods (from Feb to May and from Jun to September 2015), each period lasted 105 days (including: 15 days for adaptation + 90 days for data collection). In each experimental period, 12lactating Holstein Friesian cows with an average body weight of 557.27 kg at 3-5thlactating months, 2-6th lactation cycles and milk yield of 22.13 l/head/day were randomly allocated into a randomized complete block design comprising 4 treatments. Thecontrol group receivedbasal diet)and, three other experiment groups were added with three different levels of tannin (% DM, i.e.Group T0.3: basal diet + 0,3% tannin,group T0.5 : basal diet + 0.5% tannin,and group T0.7 : basal diet + 0.7% tannin. The basal diet composed of corn silage (14 kg/d) + tender corm stove (29 kg/d) + TMR feed (5 kg/d) + alfafa (5 kg/d) + concentrate ((milk yield - 5) x 0.5 kg/d) + natural grass (ad libitum). Tannin was directly supplemented from tea residue based on its tannin level. Results showed that tea tannin supplement increased ME intake (by 1.15%, 1.96% and 5.7%) and CP intake (by 1.49%, 2.99% and 7.09%) corresponding to T0.3, T0.5 and T0.7 diets, compared with the control. Tannin supplements at 0.3% and 0.5% levelshad no effect on digestibility but reduced digestibility at 0.7% level (by 5-10% depending on different nutrients). Tannin supplement increased milk yield (by 4.59%, 8.93% and 8.74% corresponding to T0.3, T0.5 and T0.7 diets) (P<0.05). In contrast, tannin supplement reduced total methane emissions (by 7.47%, 22.77% and 8.62%) and methane emissions intensity calculated as L/kgdry matter intake (DMI) by 8.40%, 24.06%, 17.50% or as L/kgfat corrected milk (FCM) by 20.70%, 31.58%, and 18.36% (P<0.05). As a result, tannin supplement at 0,5% DMI improved animal performance and environment efficiency.
