Thiamin Synthesis、Flows And Its Utilization In The Rumen Of Dairy Cows Under The Condition Of Different Diets

In this experiment, three Holstein dairy cows equipped with rumen cannula were used for providing rumen fluid. This study was conducted to research the synthesis、flows and utilization reqularity of thiamin using the method of combining bionic artificial rumen and in vivo. And also,3×3Latin square experiment was designed to research the effect of different NFC/NDF diets on internal environment of rumen. Those work were aimed at to attempt to supply some reference for thiamin recommended dietary allowance of ruminants under different production methods and dietary conditions. The results of this research were described as follows:In the first experiment, three Holstein dairy cows equipped with rumen fistulous were used in the3X3Latin square experiment design with23-d for each period to provide rumen fluid. The three diet treatments were a common diet group (concentrate to forage ratio50:50, NFC/NDF=1.41), a high-concentrate diet group (concentrate to forage ratio70:30, NFC/NDF=2.01), and a high-concentrate diet group supplemented with thiamine at180mg/kg. The results showed that:with the increasing of diet NFC/NDF ratio under the premise of not adding thiamin significantly decreased rumen fluid pH, NH3-N concentration and lactic acid concentration in rumen fluid increased significantly, A/P and acetate molar concentration in rumen fluid decreased significantly, propionate and butyrate molar concentration percentage in rumen fluid increased significantly. Rumen fluid pH showed a remarkable increase when diet supplementing with thiamin, rumen fluid NH3-N concentration decreased significantly when diet adding thiamin, diet supplementing with thiamin markedly decreased lactic acid concentration、 rumen fluid A/P and acetate molar concentration percentage, diet adding thiamine treatment had a markable tendency to increase propionate molar concentration percentage.These results indicated that with the increasing of diet NFC/NDF ratio could induce subacute ruminal acidosis, the alterative diet by supplementing with thiamin could improve condition of the rumen acidosis.In the second experiment, this research was conducted to study thiamin flows reqularity in ruminants rumen under the different diet conditions. Three kinds of diets were fed suecessively with different NFC/NDF1.41、1.68、2.01(concentrate to forage ratio50:50,60:40、70:30), with20-day each period, respectively. Studying thiamin circulation reqularity under the different diet conditions (common diet and high-concentrate diet of inducing rumen acidosis). The results showed that:Rumen liquid dilution rate was11.30%, thiamin circulation rate was0.73mg/h, thiamin circulation amount was17.52mg/d, rumen thiamin storage amount was6.18mg under the common diet condition. Rumen liquid dilution rate was10.81%, thiamin circulation rate was0.62mg/h, thiamin circulation amount was14.88mg/d, rumen thiamin storage amount was5.83mg under the high-concentrate diet condition of inducing rumen acidosis.In the third experiment, the bionic artificial rumen was used to research thiamin synthesis reqularity under different diet conditions. The results showed that pH expressed an upward trend after the decline, and the trend was same as the test in vivo. The results revealed that bionic artificial rumen was able to simulate the dynamic process of continuous culture in the rumen. Thiamin synthesis amount was13.86mg/d under the common diet condition. Thiamin synthesis amount was2.08mg/d under the high-concentrate diet condition. High-concentrate diet increased activity of thiamin enzymes.