Dietary Calcium and Phosphorus Levels for Reproducing Sows

Thirty-six gilts were used to evaluate three dietary Ca/P levels over a three parity period on reproductive performance. Diets formulated to contain 14% protein with total Ca/P levels of .65/.50, .80/.60 or .90/.70%, respectively, were provided during both gestation and lactation. In each group, 10 gilts were bred and two remained unbred with diets fed at 1.8 kg/d during gestation and ad libitum during lactation. Nongravid gilts were fed 1.8 kg daily during the trial. Blood samples were collected at 60 and 100 d postcoitum and both blood and milk samples at 14 and 28 d postpartum. From each lactation and each sow group, three pigs were killed at birth and six pigs at 14 and 28 d postpartum. The rib was collected for bone ash analyses with the rib, humerus and femur collected from the progeny and examined for histopathologic lesions during the second parity. After three reproductive cycles, four sows and two unbred females/group were sacrificed and bone ash determined on femur, humerus, rib and vertebrae. The results indicated no significant difference in any sow reproductive of litter performance measurement during gestation or lactation or in milk Ca and P concentration. No histopathologic bone lesions were presented in the progeny. Sow bone ash values at the end of three reproductive cycles suggested that bone demineralization from lactating animals occurred, but not uniformly for all bones. The rib, vertebrae and humerus demineralized at a greater rate than the femur. Bone ash values for reproducing sows fed the .90/.70% Ca/p treatment for three parities were similar to those of nongravid females, which were similar for all treatment groups. The results suggested an average daily intake of 50 to 55 g Ca and 40 g P to maintain bone homeostasis in lactating sows.