Comparison of apparent ileal and total tract digestibility of calcium in calcium sources for pigs

Two experiments were conducted to compare apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of calcium (Ca) in pigs. In experiment 1, three semipurified diets with soybean meal, canola meal, or sunflower meal as the sole source of Ca were formulated. Eighteen cannulated pigs (initial BW = 66 ± 5 kg) were assigned in a randomized complete block design to three treatments and six replicates per treatment. Results indicated that for either Ca or phosphorus (P), the ATTD was not different from the AID in the three diets (Psite = 0.16 and 0.81, respectively). In experiment 2, diets with four Ca concentrations were formulated with calcium carbonate as the Ca source. Sixteen cannulated pigs (initial BW = 73 ± 4 kg) were assigned in a randomized complete block design to four treatments in two experimental periods. The results indicated that the ATTD of Ca was not different from the AID for all diets. Furthermore, the Ca digestibility was not affected by dietary treatments, but the P digestibility was linearly improved (P < 0.01) as dietary Ca and P concentrations increased. Thus, it is concluded that both AID and ATTD can be used to describe the digestibility of Ca for growing–finishing pigs.