Effects Of Different Dietary Energy Composition On Lactation Performance?body Condition And Blood Biochemical Indexes Of Holstein Dairy Cows In Late-lactation

Lipids,proteins and carbohydrates are important energy nutrients in the diet of dairy cows.Different types of energy materials not only have the same energy supply function but also have their own energy supply characteristics when they meet the energy nutrition needs of dairy cows.In this study,Holstein dairy cows were fed with high starch and high fat diets prepared by changing the energy supply ratio of starch and fat in the diet.It aims to study the effect of different dietary energy compositions on the lactation performance,body condition,blood biochemical indexes and energy distribution of Holstein cows in late lactation.Fifty-two Holstein cows were used in a paired design with milk yield,body condition score and parity,twenty-six cows in each group and fed with high starch diet and high fat diet respectively.The test period consists of a 2-week pre-test and a 7-week experiment.The lactation performance,body condition and blood biochemical indexes of dairy cows were measured,calculated and compared during the experiment.The results are as follows:1.Lactation performance showed that: The milk yield(P<0.05)and energy correct milk(P<0.01)in the high starch group were significantly higher than that in the high fat group.The milk fat rate in the high fat group was significantly higher than that in the high starch group(P<0.05).The milk energy(P<0.01)in the high starch group was higher than that in the high fat group.The conversion portion of metabolic energy into milk energy in the high starch group was 1.06% higher than that in the high fat group.2.Body condition indexes showed that: The body condition score(P<0.05)and the backfat thickness(P<0.05)in the high fat group were higher than that in the high starch group.According to the difference of back fat thickness between the two groups and the change of 1 mm back fat about 5 kg body fat and 1 g body fat about 9.4 Kcal,it was calculated that the body fat deposition energy of high fat group was higher than that of high starch group,and the conversion share of metabolic energy into body fat deposition energy was 1.37% higher than that of high starch group.3.Blood biochemical indexes showed that: The blood glucose content in the high starch group was apparently higher than that in the high fat group(P<0.01),and the blood urea nitrogen content in the high starch group was significantly lower than that in the high fat group(P<0.05).The contents of triglyceride,?-hydroxybutyric acid,insulin and non-esterified fatty acid were not significantly different.In this study,it proved that the energy distribution between lactation and body tissue was affected by the composition of energy supply nutrients in the diets of dairy cows in the late lactation stage.When starch content was high in the diet for net energy supply during lactation,the amount of energy used for creating lactation increased,and when fat content was high in the diet for net energy supply during lactation,the amount of energy used for body tissue deposition increased.These results provide important technical basis for energy structure optimization and energy utilization regulation of dairy cows in the late lactation stage.