Effect of calcium and phosphorus on the incidence of leg abnormalities in growing broilers

Experiments were conducted to determine the effect of various dietary levels of Ca and P on growth and leg abnormalities in broiler cockerels fed corn and soybean meal diets varying in Ca and P content. Experiment 1 was a 2 x 4 factorial arrangement utilizing .77 and .97% Ca and .33, .38, .43, and .48% available (non-phytate) P (AP). The higher level of Ca reduced the growth rate of chicks fed low levels of AP. Neither Ca nor AP affected the incidence of crooked legs or dyschondroplasia. Increasing AP to .43% increased (P less than .05) the percentage of bone ash and bone weight. In Experiment 2, chicks were reared for 3 wk on diets containing either .40 or .50% AP. From 3 to 6 wk of age, the chicks were fed diets containing from .25 to .50% AP. The Ca:AP ratios were 2:1 in all diets. The level of AP in diets fed to 3 wk of age had no influence on chick growth, the incidence of crooked legs, or dyschondroplasia in either the starting or growing period. In Experiment 3, the chicks were reared in environmental chambers and from 3 to 6 wk of age and exposed to either constant temperature (27 C) and relative humidity (RH) (50%) or cyclic temperature (27 to 38 C) and RH (80 to 50%). The chicks were fed diets containing either .30% AP and .60% CA or .45% AP and .90% Ca from 3 to 6 wk of age. Cyclic temperature and higher RH depressed growth (P less than .05) but had no effect on the incidence of weak legs or dyschondroplasia.