Apparent ileal digestibility of amino acids by pigs is not affected by increasing dietary calcium from deficient to excess concentrations, but phosphorus digestibility is reduced

The objective was to test the hypothesis that the concentration of calcium (Ca) in diets affects apparent ileal digestibility (AID) of amino acids (AA) by pigs due to interactions between Ca, phosphorus (P), and AA. Six corn-soybean meal-based diets with Ca included at 50-175 % of the requirement were formulated. Dietary Ca was increased by increasing inclusion levels of calcium carbonate, whereas the concentration of P was constant among diets. Six growing barrows (initial body weight: 81.43 +/- 1.14 kg) were equipped with a T-cannula in the distal ileum and allotted to a 6 x 6 Latin square design with 6 diets. Ileal digesta were collected and analyzed for Ca, P, crude protein, and AA. The statistical model included diet as fixed variable and period and animal as random effects. Contrast coefficients were used to test linear and quadratic effects of increasing dietary Ca. The AID of dry matter was not affected by the level of Ca in the diets. The AID of Ca linearly (P < 0.001) increased, but the AID of P decreased in a quadratic manner (P = 0.022) with increasing Ca in diets. The AID of crude protein and all indispensable and dispensable AA was not affected by dietary Ca levels.