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.