Abstract: [Objective] To analyze the effect of feeding calcium supplementation on preventing postpartum hypocalcemia in dairy cows.[Method] 60 dairy cows with similar parity were selected and divided into 3 groups,each group had 10 first-born cows and 10 parturient cows,respectively. The group taking only 20 L warm water was set as the control group. Group Z1 was fed traditional calcium supplementation,and group Z2 was fed optimized calcium supplementation,and the preventive effects of different treatments on postpartum hypocalcemia was compared.[Result] （1）Perinatal blood ionic calcium content of first-born cows：There was no significant differences in blood ionic calcium content at 7 days before and 7 days after delivery （P>0.05）.Compared with the control group and group Z1,the fluctuation range of blood ionic calcium in group Z2 was smaller at 0 h,12 h and 7 d postpartum,and the difference among all groups was significant（P<0.05）.（2）Blood ionic calcium content of parturient cows：the variation range of perinatal blood ionic calcium of parturient cows was the same as that of first-born cattle,and the fluctuation range of blood ionic calcium in group Z2 at 0 h,12 h and 7 d postpartum was lower than that in the other two groups,and the difference among all groups was significant（P<0.05）.（3）Incidence of subclinical hypocalcemia：compared with the incidence of subclinical hypocalcemia at 0 h and 0~24 h after delivery,Z2 group<Z1 group<control group（P<0.05）.[Conclusion] Feeding Calcium supplementation can reduce the incidence of postpartum hypocalcemia in dairy cows,and the optimized calcium supplementation has better effect.

Key words: postpartum hypocalcemia, calcium supplementation, blood ionic calcium