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 2-4 parities with similar date of delivery and body weights were randomly divided into 3 groups(n=7).The cows were fed with diets of different energy levels but similar crude protein content.The NEL and crude protein levels in diets for different groups were,6.12 MJ · kg-1 and 13.03％ for group A,5.80 MJ · kg-1 and 13.01％ for group B,5.47 MJ · kg-1 and 13.03％ for group C,respectively.All the cows were fed with the same ration of ab libitum after delivery.The experiment lasted 49 d including 28 d pre-partum and 21 d postpartum.The results showed that: (1) In the beginning 1-7 d of lactation,DMI did not show obvious differences(P＞0.05) among 3 groups.Compared with group A,DMI of group C was increased by 9.93％(P＜0.01) in the following 8-14 d and increased by 8.87％(P＜0.01) during 15-21 d.(2)The milk yield had the extremely significant difference among groups(P＜0.01) at 7 d postpartum(groups C ＞ B ＞ A).Compared with group A,milk yield of group C was increased by 4.71％(P＜0.01) and 8.02％(P＜0.05) at 14 d and 21 d postpartum.(3)The body weights among the 3 groups were not significantly different(P＞0.05) during 1-14 d.At the final experimental period, the body weights were also significantly different (P＜0.01) among 3 groups at this stage(groups C ＞ B ＞A).(4) The triglyceride(TG) was not vary obviously different(P＞0.05) 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％ (P＜0.01) and 6.30％(P＜0.01) at 7 d after parturition,3.94％(P＜0.01) and 6.01％(P＜0.01) 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.
perinatalenergydry matter intakemilk yieldbody weightHolstein cowsblood index
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