Vitamin D3 toxicosis is usually an iatrogenic condition associated with excessive single or repeated parenteral or oral doses of vitamin D3. Clinical signs include anorexia, weight loss, and acetonemia. Excessive doses can lead to tachycardia, lameness, recumbency, and death. Diagnosis is based on history and clinical signs. No effective treatments are available.
Iatrogenically induced calcinosis, in the form of vitamin D3 toxicosis, is a condition that is occasionally reported in cattle and is very similar to enzootic calcinosis.
Parenteral administration of large doses of nonactivated vitamin D3 (cholecalciferol) 10–14 days before the predicted calving date is considered an effective strategy to prevent periparturient hypocalcemia (milk fever) in dairy cows; however, the narrow margin between therapeutic and toxic doses means that vitamin D3 toxicosis can occur.
Commonly, vitamin D3 toxicosis is due to the repeated injection of therapeutic doses in cows that did not calve within 2 weeks after the initial treatment and thus are considered at increased risk of developing periparturient hypocalcemia.
Clinical Findings of Vitamin D Toxicosis in Cattle
Animals with vitamin D3 intoxication become anorectic, show weight loss, and develop acetonemia within 2–3 weeks after the overdose. Tachycardia, shallow breathing, and lameness, followed by weakness, recumbency, and even death can occur in animals with vitamin D3 toxicosis.
Lesions of Vitamin D Toxicosis
Lesions of vitamin D3 toxicosis are consistent with the soft tissue calcification in enzootic calcinosis.
Diagnosis of Vitamin D Toxicosis in Cattle
History of exposure
Clinical signs
Diagnosis of vitamin D3 toxicosis is usually based on a history of repeated vitamin D3 injections, in combination with the clinical signs mentioned above.
Affected animals tend to show hyperphosphatemia, mildly to moderately elevated blood calcium concentrations, and increased renal calcium and phosphorus excretion.
25(OH)-D3 can be measured in serum during or shortly after ongoing vitamin D3 intoxication.
Treatment and Control of Vitamin D Toxicosis in Cattle
No available treatment
No practical treatment for vitamin D3 toxicosis is currently available. Education of producers concerning the risks and toxic dose of parenterally administered vitamin D3 will help avoid accidental overdoses.
Key Points
Vitamin D3 toxicosis is usually an iatrogenic problem.
Increased and prolonged absorption of calcium and phosphorus beyond requirements results in soft tissue mineralization.
No specific treatment is available.
For More Information
Littledike ET, Horst RL. Vitamin D3 toxicity in dairy cows. J Dairy Sci. 1982;65(5):749-759.
