Bioavailability of Tryptophan in Soybean Meal

The bioavailability of tryptophan in soybean meal was determined in four-week old ducks using a slope-ratio assay and carcass retention of dietary tryptophan. A diet was formulated that contained 1.13 grams of tryptophan and adequate levels of all other amino acids. Dietary supplemental tryptophan from either L-tryptophan or soybean meal linearly increased weight gain and gain-to-feed ratios. The data indicted that using weight gain and gain-to-feed ratios gave a tryptophan bioavailability value for soybean meal of 94 and 92 percent, respectively. Linear regression of tryptophan deposition in the carcass on tryptophan intake showed a 21 percent efficiency of carcass tryptophan retention above maintenance.

Adeola, O. 1998. Bioavailability of tryptophan in soybean meal and tryptophan retention in the carcasses of four-week-old ducks. Poultry Sci. 77(9):1312-1319.