Effects of calcium propionate on milk performance and serum metabolome of dairy cows in early lactation

Calcium propionate is a source of energy and calcium for alleviating negative energy balance and hypocalcemia. The objective of this study was to investigate changes in milk composition and serum metabolites associated with calcium propionate fed to postpartum dairy cows for 5 weeks. Thirty-two multiparous Holstein cows after calving were randomly allocated to control (CON), low calcium propionate (LCaP), medium calcium propionate (MCaP) and high calcium propionate (HCaP) groups. The dairy cows in the four groups were given oral drench with 0, 200, 350, 500 g/d calcium propionate per cow, respectively, from calving to d 35 in early lactation. Milk yield increased quadratically with increasing amounts of calcium propionate; being the greatest in the MCaP group. Supplementation with calcium propionate did not affect milk composition of dairy cows in early lactation. Serum glucose, insulin, glucagon, β-hydroxybutyrate, calcium, magnesium, calcitonin and calcitriol were not affected by calcium propionate supplementation. Serum non-esterified fatty acid tended to decrease linearly and parathyroid hormone increased quadratically with treatment. Serum alanine aminotransferase concentration was the lowest in the MCaP group and aspartate aminotransferase was the highest in the HCaP group among the four groups. Compared with the CON group, serum alkaline phosphatase activity decreased linearly and quadratically with the increasing calcium propionate supplementation. Supplementation with increasing amounts of calcium propionate quadratically decreased the activity of serum total antioxidant capacity, glutathione peroxidase, superoxide dismutase and catalase, however, quadratically increased concentration of malondialdehyde. Calcium propionate affected serum metabolites were mainly involved in bile acid metabolism from the metabolomic results. The 350 g/d calcium propionate feeding level could significantly improve milk performance but decrease antioxidant capacity of dairy cows as well. The effects of calcium propionate on milk performance and serum metabolites in early lactation cows was related to the regulation of serum bile acids metabolism.