A CHICK BIOASSAY APPROACH FOR DETERMINING THE BIOAVAILABLE CHOLINE CONCENTRATION IN NORMAL AND OVERHEATED SOYBEAN-MEAL, CANOLA-MEAL AND PEANUT MEAL

Our objectives were to use a soy protein isolate (SPI) diet containing 2-amino-2-methyl-1-propanol, an inhibitor of choline biosynthesis, to determine the bioavailable choline content of normal and overheated s oybean meal (SBM), canola meal (CM) and peanut meal (PM), In the first four experiments, it was determined that weight gain of chicks fed th e basal diet would respond linearly (P < 0.05) to graded levels of cry stalline choline and would not respond to betaine, and that when forti fied with adequate choline, no weight gain or feed intake response wou ld occur upon addition of 100 g/kg SBM, CM or PM to the basal diet. Fu rthermore, addition of crystalline amino acids simulating the amino ac id composition of 100 g/kg SBM did not alter the utilization of crysta lline choline, in Experiment 5, feeding graded doses of choline, SBM, CM or PM resulted in linear (P < 0.05) increases in weight gain. Multi ple linear regression analysis indicated bioavailable choline concentr ations of 1708, 1545 and 1203 mg/kg for SBM, CM and PM, respectively. In Experiment 6, no differences (P > 0.05) in bioavailable choline con centrations occurred between normal and overheated SBM, CM or PM, and the bioavailable choline concentration of normal SBM, CM and PM was 20 02, 1464 and 1320 mg/kg, respectively. Average bioavailable choline le vers were 83, 24 and 76% of analytically determined choline levels in SBM, CM and PM, respectively. Canola meal, although three times as ric h in total choline as SBM, has less bioavailable choline than SBM. A s ubstantial portion of choline in SBM, CM and PM is unavailable, and ov erheating does not appear to decrease the bioavailability of choline i n these products.