Acute vitamin D2 (ergocalciferol) toxicosis in horses: case report and experimental studies
Harrington, D.D.
Journal of the American Veterinary Medical Association 180(8): 867-873
1982
ISSN/ISBN: 0003-1488 PMID: 6979534 Document Number: 184382
Acute accidental vitamin D2 (ergocalciferol) poisoning was diagnosed in a 6-month-old foal with extensive lesions of soft tissue mineralization. In an experimental study, three 18-month-old horses were given ergocalciferol orally at 9300, 22 200, or 47 200 IU/kg of body weight/day for 21 days. Clinical signs or lesions were not seen in horses given the low and intermediate doses, whereas the horse receiving the highest dose developed clinical signs and lesions similar to those noted in the foal. Signs included depression, loss of appetite, weakness, limb stiffness with impaired mobility, and cessation of growth or weight loss. Mineralization of various soft tissues, especially of the endocardium and wall of large blood vessels, occurred in the foal and the horse given the high dose. Persistent, hyperphosphataemia (7 to 13 mg of P/dl of serum) developed in each horse. The horse given the intermediate dose remained normocalcaemic. Horses given the low and high doses became hypercalcaemic (13.6 to 14.5 mg of Ca/dl of serum), but serum calcium concentrations varied from day to day and both horses were normocalcaemic at slaughter (12.4 to 12.7 mg of Ca/dl of serum). Distal metacarpal bone ash concentrations of calcium, phosphorus, and magnesium of the foal were (mg/g of bone ash) 400.5, 180.5, and 5.3, respectively. In the horses, treatment with ergocalciferol also had little effect on serum magnesium (1.88 to 2.18 mg/dl of serum) or distal metacarpal bone ash concentrations of calcium (352.5 to 362.5 mg/g of bone ash), phosphorus (182.5 to 184 mg/g of bone ash), or magnesium (5.48 to 6.02 mg/g of bone ash).