Dietary calcium and phosphorus levels for weanling swine

Two experiments were conducted, involving 440 weanling pigs, to determine the dietary Ca and P requirements from 7 to 20 kg body weight. All diets were formulated to 20% protein from corn and soybean meal; dicalcium phosphate and limestone were used as the inorganic mineral sources with the amounts varied to meet the total dietary concentration of either mineral evaluated. In the first experiment pigs were fed five dietary Ca treatment levels ranging from .50 to 1.30% in .20% increments, while dietary P was maintained at .70%. In the second experiment (a 2 X 5 factorial) dietary Ca was provided at either .70 or .90%, while P levels ranged from .50 to .90% in .10% increments. Blood samples were collected at approximately the midpoint and end if each experiment with bones collected for ash determination at the termination of the trial. In the first study dietary Ca level did not influence gain or feed intake but did increase the feed to gain ratio as Ca increased. Mineralization of the femur, rib and humerus bone plateaued at .80% dietary Ca. In the second experiment, dietary P influenced pig gain and feed intake with a plateau at the .60% dietary P level. Serum P also plateaued at dietary P levels of .60%. Linear regression breakpoint analyses of bone ash averaged .68% P. These results suggest that the total dietary Ca and P concentration necessary for weanling pigs to attain maximum bone ash from 7 to 20 kg body weight is .80 and .68%, respectively, with corn and soybean meal based diets; whereas .1% less P is needed to maximize performance traits. The young weanling pig's calculated available P requirement is approximately .35%.