The transition period, from 21d before to 21d after calving, is viewed as a critical stage in reproductive cycle of dairy cows and influences their subsequent production performance, fertility and health. To test the hypothesis that subclinical hypocalcemia (SCH) may impair the metabolic adaptation to this period and relate to Ca homeostatic dysfunction, production performance, serum metabolic profile and calcium-regulating hormones of transition cows with different post-parturient blood Ca status were monitored from July to November 2018. Of 30 observed Holstein dairy cows, 8 which had serum Ca concentration ranging between 1.38 and 2.0 mmol/L at 24h after parturition were classified into the subclinical hypocalcemic group (LC). Normocalcemic cows were pair matched with LC ones on the basis of their initial BW and BCS (NC, 2.0<Ca<2.5 mmol/L, n=8). Body weight, BCS, milk yield, colostral and milk composition, Ca and immunoglobulin G during transition period were recorded. Blood samples were collected on -7, 1, 7, 14 and 21d relative to calving for determination of serum metabolites and calcium-regulating hormones. LC cows showed significantly lower milk production (P<0.05) during transition stage with no difference in colostral and milk composition. Cows in LC group also had significantly lower postpartum serum Ca, total protein, globulin and cholesterol concentrations than NC cows (P<0.05), while reverse was true for NEFA and BHBA. Moreover, perinatal serum Ca concentration revealed significantly negative correlations with NEFA and BHBA, and positive correlation with cholesterol and triglycerides (P<0.05). Despite no difference in blood PTH and calcitonin at 24h postpartum, significantly lower 1.25(OH)₂D was recorded in LC group (P<0.05). Our results suggest that SCH has a detrimental impact on lactation performance and post-parturient low blood Ca status is associated with energy metabolism of transition dairy cows, resulting in aggravation of lipid mobilization. These also provide evidence that suppressed 1,25(OH)₂D biosynthesis, instead of PTH, is involved in the endocrine pathogenesis of hypocalcemia.

To Cite This Article: Zhang X, Wang Z, Shah AM, Hassan MF, Peng Q, Hu R, Zou H, Wang C, Xue B, Wang L and Jiang Y, 2020. Production performance, metabolic profile and calcium-regulating hormones of transition dairy cows with different blood calcium status after parturition. Pak Vet J, 40(1): 19-24. http://dx.doi.org/10.29261/pakvetj/2019.085