| The objective of the experiment was to study the effects of dietary energy levels of pre-partum Holstein dairy cows on dry matter intake, milk yields, body weight and blood biochemical indexes during postpartum period. 21 healthy Holstein perinatal cows in 2~4 parities with the expected date of delivery and body weight were randomly classified into three groups(n=7). The cows were fed diets with different energy levels and the similar crude protein content. The NEL and crude protein levels of diet were 6.12 MJ/kg and 13.03% for group A, 5.80 MJ/kg and 13.01% for group B, 5.47 MJ/kg and 13.03% for group C, respectively. After delivery,all the cows were provided with the same ration ad libitum feeding. The experiment lasted 49 d(28 d pre-partum and 21 d postpartum).The results show that DMI and body weight didn`t differ significant(P>0.05), but the milk yield had the extremely significant difference among groups(P<0.01) in the one week after parturition. In the second week, comparing to group A, DMI and milk yields of group C were increased by 9.92%(P<0.01) and 16.36%(P<0.01), but body weight difference was not significant. In the third week after postpartum, DMI and milk yields and body weight of group C were increased by 8.84 %(P<0.01) and 8.02 %(P<0.05) and 8.66 %(P<0.01) than that of group A. The calves weight were not significant of three groups(P>0.05). The milk composition had not significant difference unit 21 d postpartum(P>0.05).The group of low energy was higher on each nutrient apparent digestibility. The apparent digestibility of CP in Group C was very higher than group A(P<0.01), the NDF and ADF were highest(P<0.01). The apparent digestibility of Ca and P in Group C were significantly higher than group A(P<0.05). The nutrient apparent digestibility had not significant difference among three groups in postpartum(P>0.05).The highest group of Glucose(Glu) concentration was group A in the prenatal and the group C in the postpartum. Among three groups, the triglyceride(TG) concentration didn`t differ significant(P>0.05),but the prenatal was significantly higher than postpartum. The concentration of ALT has a trend that upward then downward, there was positive correlation between ALT and energy levels at prenatal. The concentration of AST was increased gradually, the group A was significantly higher than group C in 14 d prenatal, 7 d and 21 d postpartum(P<0.05).Leptin has a trend of downward, in 14 d and 21 d postpartum, the concentration of leptin of group C were increased by 5.93%(P>0.05)and 1.25%(P>0.05) than that of group A. NPY has a trend of upward with the reduced of energy level. In 7 d,14 d and 21 d postpartum, the concentration of leptin of group C were increased by 4.63%(P>0.05),13.99%(P<0.01) and 10.29%(P>0.05) than that of group A. On the day of birth, the concentration of the Growth hormone(GH) of group B and C had increased by 9.29%(P<0.01) and 16.43%(P<0.01) than group A, In the 21 d after parturition, the group B and C had increased 23.17%(P<0.01) and 15.85%(P<0.01) than group A, respectively. Theβ-hydroxybutyric acid(BHBA) didn`t differ significant(P>0.05).In the 7 d after parturition, the nonesterified fatty acids(NFEA) levels of group B and C were reduced by 3.80%(P<0.01) and 6.30%(P<0.01) than that of group A, the levels were reduced by 3.94%(P<0.01) and 6.01%(P<0.01), respectively.The activity of pyruvate carboxylase has a trend that upward then downward. phosphoenolpyruvate carboxylase was increased in the trial period, group B and group C were increased by 9.78%(P<0.05) and 18.82%(P<0.01) than A in the day of birth, increased by 13.17%(P<0.05) and 26.39%(P<0.01) in the 14 d after parturition, increased by 2.77%(P<0.05) and 11.47%(P<0.01) in 21 d postpartum.All the analysis shows that decreasing the energy level of pre-partum was helpful not only to increase the DMI and milk yield, concentration of blood glucose and enzyme activity of PC and PEPCK, but also significantly reduce cows` weight loss and NEFA concentrations in the blood at postpartum under the condition of this experimental that the energy level was below the NRC(2001) and China nutrient requirements of dairy cow. These effects can alleviating energy negative balance of perinatal cows. |
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