Effect Of Thiamin On The Digestion And Metabolism Of Rumen Nutrient Substance In Vitro

Three healthy XuHuai wethers fitted with permanent ruminal cannulas were used in the present research. The artificial rumen for incubation, enzyme activity analysis, and molecular biology techniques were used to investigate influence of Thiamin on the digestion and metabolism of rumen nutrient substance in vitro under different dietary type and different levels of sulphur adding Thiamin,and attempt to supply some references for the further study of Thiamin in the rumen.In the first experiment, the objectives of this part were to study the effect of Thiamin on ruminal internal environment parameters on low-concentrate diet.The in vitro culture were conducted using semi-pure diet consisted of a mixture of 63.0g milled filter paper,6.0g pectins,7.0g xylan,18.0g wheat starches and 6.0g soluble starches ,the concentrate/forage ratio is 30:70. The results showed that there were no significant differences in pH among five levels of thiamin (P>0.05); NH3-N concentration in culture fluid increased when adding thiamin; Thiamin increased ruminal protozoal protein yield whereas the yield of ruminal bacterial protein was decreased, and the ratio of protozoal protein and bacterial protein was significantly increased;the concentrations of acetate,propionate and total VFAs were decreased.It was also found that Thiamin increased the concentrations of butyrate and the proportion of butyrate and acetate, and decreased the proportion of propionate;the acetate/propionate ratio keeppd balance state; the concentration of the lactate was reduced,and 20mg/kg Thiamin had significant effect compared with control group(P<0.01)In the second experiment,the effect of Thiamin on the digestion and metabolis of rumen nutrient substance on high-concentrate diet was investigated in vitro. Semi-pure diet as substrates used in the culture included 27.0g milled filter paper,14.5g pectins,3.0g xylan,41.0g wheat starches and14.5g soluble starches,the concentrate/forage ratio is 70:30.The adding level of Thiamin were designed as A(0mg/kg),B(30mg/kg), C(60mg/kg),D(90mg/kg),E(120mg/kg). The results showed that Thiamin reduced average pH and NH3-N concentration,but increased pH at 24h. There were no significant differences in the yield of MCP, the ratio of protozoal protein and bacterial protein was waved. The concentrations of propionate,butyrate and total VFAs and the proportion of acetate and propionate increased, as well as the acetate/propionate ratio decreased when adding thiamin. Thiamin increased the fibre degradability,and the degradability of 30mg/kg,60mg/kg,90mg/kg and 120mg/kg treatments were increased by 41.67%(P>0.05),74.98%(P<0.01),58.60%(P<0.05)and 50.14%(P<0.05)than the control at 24h respectively. There were no significant differences in activity of pectin enzyme and reduced the activity of cellulose enzyme. The activity of xylan enzyme increased and 60mg/kg treatment was significant higher than the control. Thiamin increased the total concentration of Thiamin while decreased the concentration of the lactate.The third experiment was conducted to determine the effect of Thiamin on rumen fermentation and rumen microbes, a 2×2 two factorial design of experiment was adopted:one factor was different nitrogen /sulphur ratios(6:1,16:1), the other was adding Thiamin or not(0mg/kg and60mg/kg). The results showed that there had no significant effect on pH and NH3-N concentration. The high S level restrained the synthesis of bacterial protein and significantly decreased the ratio of protozoal protein and bacterial protein(P<0.05). There were no effect on the concentrations of acetate,propionate and the acetate/propionate ratio.The low S level increased the concentration of butyrate,total VFAs and the proportion of butyrate,and the high S level reduced the total concentration of Thiamin while the total Thiamin was increased adding Thiamin.,and the high S also decreased the concentration of the lactate.Compared to the group which didn't added Thiamin, the number of Strepococcus bovis of adding Thiamin group decreased by 5.90% and 2.05% on the same nitrogen /sulphur ratios,and there had no significant effect on the number of Butyrivibrio fibrisovens.