Diet-induced pseudohypoparathyroidism: A hypocalcemia and milk fever risk factor.

Abstract

Subclinical hypocalcemia may affect half of all multiparous cows, and clinical hypocalcemia or milk fever affects approximately 5% of dairy cows each year. This disorder of calcium homeostasis can be induced by several dietary factors. Recent studies implicate high dietary potassium and high dietary cation-anion difference (DCAD) with increased risk of milk fever. The hypothesis tested in this study was that high-DCAD diets fed to prepartum cows reduce tissue sensitivity to parathyroid hormone (PTH), inducing a pseudohypoparathyroid state that diminishes calcium homeostatic responses. Multiparous Jersey cows were fed low- or high-DCAD diets in late gestation, creating a compensated metabolic alkalosis in the high-DCAD cows and a compensated metabolic acidosis in the low-DCAD cows. They then received synthetic PTH injections at 3-h intervals for 48 h. Parathyroid hormone is expected to cause an increase in plasma calcium by increasing renal production of 1,25-dihydroxyvitamin D and increasing bone calcium resorption. Plasma calcium concentration increased at a significantly lower rate in cows fed the high-DCAD diet. Cows fed the high-DCAD diet also produced significantly less 1,25-dihydroxyvitamin D in response to the PTH injections than cows fed the low-DCAD diet. Serum concentrations of the bone resorption marker carboxyterminal telopeptide of type I collagen were numerically lower in cows fed the high-DCAD diet but this difference was not statistically significant. These data provide direct evidence that high-DCAD diets reduce tissue sensitivity to PTH. The metabolic alkalosis associated with high-DCAD diets likely induces a state of pseudohypoparathyroidism in some dairy cows at the onset of lactation, resulting in hypocalcemia and milk fever.

• Authors: J P Goff, A Liesegang, R L Horst
• Journal: Journal of dairy science (J Dairy Sci) Vol. 97 Issue 3 Pg. 1520-8 (Mar 2014) ISSN: 1525-3198 [Electronic] United States
• PMID: 24418271 (Publication Type: Journal Article)
• Copyright: Copyright © 2014 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Chemical References

• Parathyroid Hormone
• Vitamin D
• 1,25-dihydroxyvitamin D
• Creatinine
• Cathepsin K
• Magnesium
• Calcium

Topics

• Animals
• Calcium (blood, urine)
• Cathepsin K (metabolism)
• Cattle
• Cattle Diseases (blood, etiology, pathology)
• Creatinine (urine)
• Diet (adverse effects, veterinary)
• Female
• Hypocalcemia (etiology, veterinary)
• Lactation
• Magnesium (blood, urine)
• Parathyroid Hormone (administration & dosage, blood)
• Parturient Paresis (blood, etiology, pathology)
• Pregnancy
• Pseudohypoparathyroidism (etiology, veterinary)
• Risk Factors
• Vitamin D (analogs & derivatives, blood)