| Four experiments were conducted to investigate the effects of condensed tannins and hydrolyzable tannins additions on ruminal protein protection, microbial synthesis,nitrogen utilization, methanogen and nitrogen emissions in dairy cows, and to explore possible mechanism on utilization of dietary nitrogen and nitrogen emissions in dairy cows with condensed tannins and hydrolyzable tannins additions.Experiment1, Myrica rubra (Lour.)Zucc and Acacia mangium condensed tannins were distilled water and was added to the experiment feeds (soybean meal) to achieve ratios of0,300,600or900mg CT/g experiment feeds DM. Experiment feeds were incubated at39℃for12h to allow the CT to interact with the CP. Vilonia hydrolyzable tannins and soybean meal directly mixed in dry form. This experiment were conducted to investigate the effects on In situ degradability and intestinal digestibility of soybean meal with condensed tannins and hydrolyzable tannins additions. Addition of condensed tannins and hydrolyzable tannins significantly reduced In situ rumen protein digestibility of soybean meal, Addition of Myrica rubra (Lour.)Zucc condensed tannins at30,60, and90g/kg DM decreased In situ rumen protein digestibility by14.5,18.9and25.4%, Addition of Acacia mangium condensed tannins at30,60, and90g/kg DM decreased In situ rumen protein digestibility by18.4,24.5and38.8%, Addition of valonia hydrolyzable tannins at30,60, and90g/kg DM decreased In situ rumen protein digestibility by19.7,25.1%and33%.Rumen protein effective degradability of soybean meal showed a downward trend with addition concentration increasing of condensed and hydrolyzable tannin(P<0.05), there existed a significant interaction effect on rumen protein digestibility between the concentration and source of tannins (P<0.05); the intestinal protein digestibility of rumen undegraded protein of soybean meal with condensed and hydrolyzable tannins addition.Experiment2, method was applied in experiment1, Acacia mangium condensed tannins and valonia hydrolyzable tannins was mixed to the feed with different ratio of RDP to RUP, tannin concentration was0%,3%,6%and9%respectively, ratio of RDP to RUP was feed A (2.25:1); feed B (1.76:1); feed C (1.4:1) respectively. This experiment was conducted to investigate the interaction effects on in vitro rumen fermentation and in situ digestibility between the concentration of tannins and different ratio of RDP to RUP in feed. with the increasing of Acacia mangium condensed tannins condensation, rumen microbial protein synthesis, gas production parameters "a" and "b" decreased linearly (P<0.05), There was significant effect in terms of rumen microbial protein synthesis, gas production parameters "a" and "b" between the concentration of tannins and different ratio of RDP to RUP in feed (P<0.05); significant interaction effect was observed in terms of rumen protein effective degradability between the concentration of tannins and different ratio of RDP to RUP in feed (P<0.001). with the increase of valonia hydrolyzable tannins condensation, gas production parameters "a" decreased linearly in feed A(.P<0.001) and feed B(P<0.05), There was significant effect in terms of gas production parameters "a" between the concentration of tannins and different ratio of RDP to RUP in feed (P<0.001), significant interaction effect was observed in terms of rumen protein effective degradability between the concentration of tannins and different ratio of RDP to RUP in feed (P<0.001), with the increase of valonia hydrolyzable tannins condensation, gas production parameters "b" decreased linearly in all feed (P<0.05), rumen microbial protein synthesis, significant interaction effect was not observed between the concentration of tannins and different ratio of RDP to RUP in feed (P>0.05), microbial protein synthesis was not affected with valonia hydrolyzable tannins addition in feed A and B group (P>0.05),but linearly declined in feed C group (P<0.05), there was not significant interaction effect in terms of microbial protein synthesis between the concentration of tannins and different ratio of RDP to RUP in feed (P>0.05), significant interaction effect was observed in term of rumen protein effective between the concentration of tannins and different ratio of RDP to RUP in feed (P<0.001).Experiment3, feed treated with tannins in experiment2was used. This experiment was conducted to investigate the effects on rumen methane emissions, microbial synthesis and methanogen of soybean meal with condensed tannins and hydrolyzable tannins additions. With the increase of Acacia mangium condensed tannins concentration, the proportion of methane in total gas was decreased linearly (P<0.05), Addition of Acacia mangium condensed tannins at30,60, and90g/kg DM decreased CH4by12.6%,29.8%and44.9%, showed a highly significant linear decrease (P<0.001), proportion of methanogens to total bacteria showed a significant linear decrease (P<0.05). With the increase of valonea hydrolyzable tannins concentration, proportion methane to total gas showed downward trend (P>0.05), Addition of valonea hydrolyzable tannins at30,60, and90g/kg DM decreased CH4by by4.1%,11.8%and20.4%, was showing highly significant linear decrease (P<0.05), proportion of methanogens to total bacteria decreased linearly (P<0.05).Experiment4, four Holstein cows were used in a4×4Latin square design to determine the effects of condensed tannins and hydrolyzable tannins additions(3%DM) on ruminal microbial synthesis,nitrogen utilization and nitrogen emissions in dairy cows. Addition of condensed and hydrlyzable tannins did not affect feed intake, milk yield,4%fat-corrected milk yield, energy corrected milk yield, milk protein percentage, milk fat percentage, milk lactose percentage (P>0.05), but significantly reduced the MUN concentration (P<0.05). Addition of condensed and hydrlyzable tannins did not affect the intake of dry matter, crude protein, NDF and ADF in dairy cows (P>0.05). Addition of Acacia mangium of condensed tannins and valonia hydrolyzable tannins significantly decreased DM digestibility by6.8%and24%in dairy cows respectively (P<0.01), and Addition of Acacia mangium of condensed tannins significantly decreased NDF and ADF digestibility by7.4%and8.5%. Addition of Myrica rubra (Lour.)Zucc condensed tannins increased dietary CP digestibility by4%(P<0.05), But Addition of Acacia mangium of condensed tannins and valonia hydrolyzable tannins decreased CP digestibility by19%and11%(P<0.05). Addition of Myrica rubra (Lour.)Zucc condensed tannins increased microbial purine production by14%(P<0.05), Addition of Valonia hydrolyzable tannins showed an upward trend(P>0.05), Addition of Acacia mangium condensed tannins decreased microbial purine production by5%(P<0.05). Addition of condensed tannins and hydrolyzable tannins did not affect dietary nitrogen utilization efficiency (P>0.05), but net excretion of urinary nitrogen reduced (P<0.05), and changed the ratio of fecal nitrogen to urinary nitrogen (P<0.05), Addition of Myrica rubra (Lour.)Zucc condensed tannins decreased urinary nitrogen and fecal nitrogen excretion(P <0.05), Addition of Acacia mangium condensed tannins and valonia hydrolyzable tannins increased fecal nitrogen and urinary nitrogen excretion (P<0.05). |
