Effect of Dietary Energy Levels on Postpartum Performance and Blood Biochemical Indexes of Pre-partum Holstein Dairy Cows

The objective of this study was to measure the effects of dietary energy levels of prepartum Holstein dairy cows on dry matter intake,milk yield,body weight and blood biochemical indicators at postpartum stage.21 healthy pre-partum Holstein cows in 2-4parities with similar date of delivery and body weights were randomly divided into 3groups(n=7).The cows were fed with diets of different energy levels but similar crude protein content.The NELand crude protein levels in diets for different groups were,6.12MJ·kg-1 and 13.03%for group A,5.80MJ·kg-1and 13.01% for group B,5.47 MJ·kg-1 and 13.03% for group C,respectively.All the cowswere fed with the same ration of ab libitum after delivery.The experiment lasted 49dincluding28dpre-partum and 21 dpostpartum.The results showed that:(1)In the beginning 1-7dof lactation,DMI did not show obvious differences(P0.05)among 3groups.Compared with group A,DMI of group C was increased by 9.93%(P0.01)in the following 8-14 dand increased by8.87%(P0.01)during 15-21 d.(2)The milk yield had the extremely significant difference among groups(P0.01)at 7dpostpartum(groups C B A).Compared with group A,milk yield of group C was increased by 4.71%(P0.01)and 8.02%(P0.05)at 14 dand 21dpostpartum.(3)The body weights among the 3groups were not significantly different(P0.05)during 1-14 d.At the final experimental period,the body weights were also significantly different(P0.01)among 3groups at this stage(groups C B A).(4)The triglyceride(TG)was not vary obviously different(P0.05)among groups.The highest Glucose(Glu)was observed in group A in the pre-natal stage,but group C at the postpartum stage.In comparison with group A,the nonesterified fatty acids(NEFA)levels of group B and C were reduced by 3.80%(P0.01)and 6.30%(P0.01)at 7dafter parturition,3.94%(P0.01)and 6.01%(P0.01)at 14 d,respectively.Decreasing the energy level of pre-partum diet not only improve the DMI,milk yield and blood glucose concentration,but also significantly reduce cows' weight loss and NEFA concentrations in the blood at postpartum.It all suggests that low energy level of pre-partum diet could alleviate negative energy balance(NEB)of perinatal cows.