The effect of different totals and ratios of dietary calcium and phosphorus on the performance and incidence of leg abnormalities of male and female broiler chickens.

A factorial experiment involving 1,404 day-old Shaver broiler chicks (702 of each sex) assessed the effects of total calcium (Ca) and available phosphorus (AP) and their ratio (Ca: AP) during the starter (0 to 21 days) and finisher (22 to 42 days) periods on general performance, tibia strength, tibia ash, Ca and P content of tibia ash, tibia dyschondroplasia, twisted legs, and total leg abnormalities. Nine starter and nine finisher diets were used with the percentage Ca and AP ranging from .98 to 1.47 and .39 to .67, respectively, for the starters and from 1.00 to 1.40 and .32 to .51, respectively, for finishers. In general, optimum weight gain, live body weight, feed conversion, tibia strength, tibia dry weight, and tibia ash were obtained when the highest Ca + P was fed, but lower Ca:AP ratios were also effective for some traits. Tibial dyschondroplasia (TD) and total leg abnormalities, however, were highest when these diets were fed. The results indicate that the ratio of Ca:AP in the diet is a determining factor in causing TD in broiler chickens. As the ratio of Ca:AP in the diets widened in response to increased Ca or decreased P, the incidence of TD and total leg abnormalities decreased (P less than .05).