Biological values of phosphorus from various sources for young turkeys

Two experiments, each utilizing 540 turkeys, were conducted to determine the biological value of phosphorus from 13 different sources when compared with that from dicalcium phosphate (dihydrate, purified) as a standard. Each phosphorus source was added to a basal diet composed of 44% ground yellow corn and 52% dehulled soybean meal to supply .09, .18, .27, or .45% inorganic phosphorus. Each of 60 diets, which included duplicates of the standard source, was fed to a pen of 9 male poults from 1 day to 3 weeks of age in each experiment. Body weight and toe ash measurements of poults collected at 3 weeks of age were used in nonlinear (exponential) bioassays to obtain relative biological values of phosphorus from various sources. With the dicalcium phosphate standard set at 100%, the average relative biological values of three samples from each of commercial monocalcium phosphate (21% P), dicalcium phosphate (18.5% P), and defluorinated phosphate were 93, 81, and 70%, respectively. Four samples of experimental defluorinated phosphate averaged 75%. Differences of about 5% between values were required for statistical significance, indicating significant differences among these biological values of phosphorus from the various phosphate sources in diets of young turkeys.