Chronic ingestion of high concentrations of cholecalciferol in cats

Objective - To determine whether ingestion of 63 times the recommended amount of vitamin D₃ (cholecalciferol) results in renal calcification or damage in cats. Animals - 20 four-month-old kittens, 17 queens, and 20 kittens born to these queens. Procedure - 4-month-old kittens and queens were given a purified diet with 846 μg of cholecalciferol/kg of diet (high vitamin D₃ diet) or 118 μg of cholecalciferol/kg of diet (control diet) for 18 months. Kittens born to queens were weaned onto the same diet given to dams. Results - There were no apparent adverse effects of the high vitamin D₃ diet. Plasma cholecalciferol and 25-hydroxycholecalciferol (25-OHD₃) concentrations of queens and 4-month-old kittens given the high vitamin D₃ diet significantly increased with time. At 6 months, plasma cholecalciferol concentrations in these kittens and queens were 140.0 ± 7.3 nmol/L and 423.6 ± 26.6 nmol/L, respectively (10 times initial values). Corresponding 25-OHD₃ concentration in queens was 587.5 ± 59.4 nmol/L (2.5-fold increase over initial values). At 3 months of age, kittens born to queens given the high vitamin D₃ diet had an increase in serum BUN and calcium concentrations and a decrease in RBC and serum total protein, albumin, and hemoglobin concentrations. By 18 months, these kittens had an increase in plasma cholecalciferol (276.0 ± 22.2 nmol/L) and 25-OHD₃ (1,071.9 ± 115.3 nmol/L) concentrations. However, all indices of renal function and the appearance of renal tissue on histologic evaluation were normal. Conclusions and Clinical Relevance - These results indicate that cats are resistant to cholecalciferol toxicosis when the diet is otherwise complete and balanced.