Impact of Clinoptilolite and Anionic Salts on Calcium Homeostasis, Parathyroid Hormone, and Related Metabolic Parameters in Periparturient Dairy Cows

This study compared the regulatory effects of dietary supplementation with natural clinoptilolite (CLN) versus a dietary cation-anion difference (DCAD) regimen on calcium homeostasis in dairy cows during the last 21 days prepartum. Results showed that cows in the DCAD group exhibited significantly higher blood ionized calcium (iCa) and parathyroid hormone (PTH) concentrations than those in the CLN group (p < 0.05). Serum PTH concentrations displayed a declining trend in both groups prepartum, which deviates from the classical theory of compensatory PTH secretion, suggesting that alternative compensatory pathways may be involved in the regulation of calcium homeostasis during the periparturient period in dairy cows. Monitoring of calcium homeostasis and related metabolic parameters following postpartum oral calcium bolus administration revealed that the incidence of subclinical hypocalcemia in the DCAD group was 26%, lower than the 62% observed in the CLN group. However, blood iCa concentrations returned to normal levels more rapidly in the CLN group. Additionally, CLN supplementation was associated with more stable blood pH and lower prepartum serum potassium concentrations (p < 0.05) that remained within the physiological range, which may contribute to improved tissue sensitivity to PTH.