RESUMO
Two experiments were conducted to evaluate the effects of calcium (Ca) levels in weanling pigs (Landrace × Yorkshire × Duroc). In experiment 1, one hundred and eighty weanling pigs were randomly allotted to one of the three treatments. The treatments were low (Ca 0.60% in phase 1 and 0.50% in phase 2), standard (Ca 0.72% in phase 1 and 0.66% in phase 2), and high (Ca 0.84% in phase 1 and 0.72% in phase 2). In experiment 2, hundred and forty weanling pigs were randomly assigned to one of four treatments differing in Ca levels (high and low) and sources (CaCl2 and CaCO3) in a 2 × 2 factorial arrangement. There were 10 pigs per replicate in both experiments, with 6 replicates in each treatment, and they were conducted in two phases (phase 1, days 0-14; phase 2, days 15-28). In experiment 1, body weight (BW), average daily gain (ADG), and growth to feed ratio (G/F) increased as the Ca level decreased (p < 0.05). P digestibility was higher in the low-Ca diet group than in the high-Ca diet group (p <0.05). In experiment 2, the final BW, ADG, and G/F increased in the CaCl2 diet group compared with the case in the CaCO3 diet group (p < 0.05). The digestibility of crude protein (CP), Ca, and P was higher in the CaCl2 diet group than in the CaCO3 diet group (p < 0.05). Cl- levels were higher in the CaCl2 diet group than in the CaCO3 diet group (p < 0.05). The bicarbonate (HCO3 -), base excess (BE), and electrolyte balance (EB) levels were lower in the CaCl2 diet group than in the CaCO3 diet group (p < 0.05). Hematocrit increased as the Ca level decreased (p < 0.05). The HCO3 - interacted with the Ca sources and thus, affected the Ca levels (p < 0.05). Bone ash, Ca, and P were downregulated in the low-Ca diet group compared with the case in the high-Ca diet group. Overall, the low dietary Ca supplementation led to greater growth performance. Furthermore, CaCl2 appeared to be a better Ca source than CaCO3 because of the greater digestibility of CP, Ca, and P, and improved EB.