Assessment of the quantity of biologically available choline in soybean meal.

Growth assays were conducted with 8-dayold crossbred chicks to evaluate the available choline in 44 and 49% protein soybean meals, and also in whole heat-treated soybeans. A choline-free (experimental basal d i e t ) p r e t e s t diet was imposed from day 5 to 8 posthatching to diminish choline stores. Soybean sources were added at 5 and 10% to the basal diet, and a choline response curve was generated using 0, 175, and 350 ppm choline contr ibuted from crystalline choline chloride. Slope-ratio and standard curve techniques were used to quantify the available choline content of each ingredient tested. Two sources of dehulled soybean meal were found to contain 1,614 and 2,026 ppm available choline, respectively. The latter sample was also evaluated in the presence of 2-amino-2-methyl-l-propanol, a specific inhibitor of choline biosynthesis, and a value of 2,024 ppm was obtained. The whole bean and 44% CP soybean meal were found to contain 1,844 and 1,664 ppm available choline, respectively. Using accepted table values (2,850, 2,743 and 2,420 ppm for dehulled, regular and whole bean, respectively) the availability of choline in the soybean products tested appears to range between 60 and 75%. (