| The metabolism of dairy cows is exuberant in transition and this is a crucial period indairy production cycle. However, it is quite common that the nutrient intake cannot meet therequirements of body in transition, especially for energy intake, which induce negative energybalance (NEB) in dairy cows. At the same time, dairy cows fulfill their body requirements byincreasing the metabolism rate of body fat, which can result in fatty liver and ketosis easily.The hepatic fat is either oxidized for offering energy or exported by the form of very lowdensity lipoprotein (VLDL) in dairy cows and choline can promote the β-oxidizing of fattyacid and the synthesis of VLDL. Therefore, the NEB can be mitigated and the accumulationof fat in liver can be decreased, the occurrence of energy metabolism diseases will reduceconsequently. Twenty-four Holstein cows in transition were selected in our experiment. Thecows were assigned equally to a control group and an experimental group according tomatched-pair grouping design. Dairy cows in experimental group were fed total mixed ration(TMR) supplemented with60g rumen-protected choline (RPC) every day during21daysbefore calving and21days after calving. Dairy cows in the control group were only fed TMR.All the cows’ blood samples (21d,14d,7d before calving;0d,7d,14d,21d after calving)and milk samples (0d,7d,14d,21d after calving) were taken to test periodically. Theresults showed that the plasma glucose (P=0.014) and VLDL (P=0.043) of experimentalgroup were increased, while plasma non-esterifed fatty acid (P＜0.001) and β-hydroxybutyricacid (P=0.001) were decreased. The contents of total solids (P=0.031) and non-fat solids(P=0.038) in milk were higher in experimental group than in control group. There was nosignificant difference (P＞0.05) in plasma triglyceride, total bilirubin, total protein, albumin,glutamic pyruvic transaminase, glutamic oxaloacetic transaminase, alkaline phosphatase, andurea nitrogen. This study has demonstrated that RPC can mitigate energy metabolism andmilk composition of dairy cows in transition. |
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