Dietary calcium and phosphorus levels for growing swine from 18 to 57 kilograms body weight.

A randomized complete block design experiment was conducted using 408 crossbred pigs to evaluate the effects of six dietary Ca/P levels for growing swine (18 to 57 kg). Total dietary P levels ranged from .40 to .90% in .1% intervals with Ca concurrently increased at a 1.3:1 ratio in a 16% protein corn-soybean meal diet. Dicalcium phosphate and limestone were the source of inorganic Ca and P. For the overall trial, daily gain and feed intake improved as dietary Ca/P increased to an approximate level of .65/.50%. An inverse relationship occurred between serum Ca and P, with serum Ca declining and P increasing at the lower mineral levels. Femur, humerus, rib, metatarsal and metacarpal ash content increased quadratically (P less than .01) as dietary Ca/P increased with suggested dietary breakpoint inflections of .90% Ca and .70% P at 40 kg, and at .72/.55% levels at 57 kg body weight. Percentage ash of the head portion of the bone was lower than the shaft section. Bone shaft thickness and bending moments for metatarsals and metacarpals increased as dietary Ca/P levels increased, with higher values and higher dietary inflection points at 57 than at 40 kg body weight. Bone length was not influenced by dietary Ca/P level, but fat-free dried bone weight was, resulting in higher total bone ash and organic weight as Ca/P level increased.