Growing Kittens Require Less Dietary Calcium than Current Allowances

We previously demonstrated that a purified diet containing 3.125 μg of cholecalciferol/kg was adequate to maintain plasma concentrations of 25-hydroxyvitamin D in growing kittens. With the use of this concentration of cholecalciferol, the response of growing kittens to varying levels of calcium in purified diets was measured. Five groups (treatments 1–5), each comprised of seven weaned kittens, were given diets containing 3.8, 5.0, 6.0, 7.2 or 8.1 g calcium/kg diet (Ca:P ratio of 1:1.25) from 9 to 18 wk of age. Two further groups of kittens (treatments 6 and 7) received similar diets containing 6.0 g Ca/kg diet, with Ca:P ratios of 1:1.55 and 1:2.61, respectively. No clinical signs of calcium deficiency were observed, i.e., growth rate, energy intake and plasma total calcium were not affected by the treatments. However, ionized calcium was significantly lower in kittens in treatment 7. Plasma phosphorus was lower in kittens in treatment 7 than in kittens in treatments 1, 2, 3 and 4, and there was a negative relationship between dietary and plasma phosphorus concentrations. Kittens in treatment 7 had a significantly higher alkaline phosphatase concentration in plasma than kittens in treatments 1, 2, 3 and 5. Kittens in treatment 1 had a lower percentage of bone minerals measured by dual-energy X-ray absorptiometry than kittens in treatments 2–6. These results indicate that the calcium requirement of growing kittens is not >6.0 g/kg diet, (calculated metabolizable energy ∼20 kJ/g) and that kittens are not very sensitive to inverse Ca:P ratios up to 1:1.55.