Abstract: [Objective] This experiment aimed to study the preventive and therapeutic effects of the new calcium supplement pills on postpartum hypocalcemia in dairy cows. [Method] Thirty-four healthy multiparous dairy cows of more than two litters were selected and randomly divided into two groups,with 17 cows in each group. The cows in the experimental group （EG group） were given the new calcium supplement pills,while the cows in the control group （CG group） were given the commonly used calcium supplement. Tail-root venous blood samples were collected at four time points （0 hours postpartum,2 hours after the first administration of calcium supplement,12 hours after the first administration of calcium supplement,and 2~4 hours after the second administration of calcium supplement） to determine the content of blood mineral elements,blood gas indicators,and blood biochemical indicators. The average milk production and the incidence of metabolic diseases within 30 days postpartum were also recorded. [Result] The results showed that：1）After administration of two calcium supplements,the postpartum blood ionic calcium （iCa） content of all dairy cows at the four time points increased. Moreover,after the two administration of calcium supplements in the EG group,the increase in blood calcium was significantly better than that in the CG group. 12 hours after the first administration,the iCa content in the EG group was significantly higher than that in the CG group （P<0.05）. Two - four hours after the second administration of calcium supplements,the contents of sodium ions （Na⁺） and potassium ions （K⁺） in the blood of all dairy cows were significantly higher than those at 0 hours postpartum （P<0.05）. 2） The blood acid-base balance index of dairy cows in the EG group was significantly higher than that in the CG group 12 hours after the first administration of calcium supplement （P<0.05）. The comparison results of blood gas indicators at different time points showed that 12 hours after the first administration of calcium supplement and 2~4 hours after the second administration of calcium supplement in the EG group of dairy cows,the blood acid-base balance index and bicarbonate （HCO₃^-） in the blood were significantly higher than those at 0 hours after delivery and 2 hours after the first administration of calcium supplement （P<0.05）. The total carbon dioxide （TCO₂） content in the blood of dairy cows in the EG group 12 hours after the first administration of calcium supplement and 2~4 hours after the second administration of calcium supplement was significantly higher than that in the EG group 0 hours after delivery （P<0.05）. 3） After postpartum administration of two calcium supplements to dairy cows,the contents of blood glucose （Glu）,hematocrit （Hct）,and hemoglobin （Hb） in both the EG group and the CG group showed a downward trend. Moreover,in the CG group,2~4 hours after the second administration of calcium supplements,the contents of hematocrit （Hct）,blood glucose（Glu）,and hemoglobin （Hb） were significantly lower than those at 0 hours postpartum （P<0.05）. 4） The average milk production of dairy cows in the EG group was significantly higher than that in the CG group （P<0.05）,and the incidence of postpartum diseases in EG dairy cows was lower than that in the CG group. [Conclusion] To sum up,postpartum administration of the new calcium supplement pills to dairy cows can rapidly increase blood calcium concentration and reduce the incidence of postpartum hypocalcemia. Compared with the postpartum calcium rods commonly used in domestic pastures at present,its effect of increasing blood calcium is more significant. This pill helps maintain electrolyte,acid-base balance and energy metabolism homeostasis,thereby reducing the negative impact of calving stress on the production performance of dairy cows and providing a new option for the management of perinatal hypocalcemia in dairy cows.

Key words: calcium supplement pill, dairy cows, hypocalcemia, blood calcium concentration