The bioavailability of lysine and phosphorus in distillers dried grains with solubles

Five experiments were conducted to determine Lys and P bioavailabilities of distillers dried grains with solubles (DDGS), which was derived from corn fermentation in a modern nonbeverage ethanol plant. In experiment 1, we used the precision-fed cecectomized rooster assay and estimated the true digestibility of Lys in DDGS to be 75%. In experiments 2, 3, 4, and 5 the relative bioavailabilities of Lys and P were assessed using slope-ratio chick growth experiments. In experiments 2 and 3, Lys-deficient basal diets containing 0.40 or 0.60% digestible Lys respectively, were formulated. A linear growth response (P < 0.05) was observed from the addition of 0.10 and 0.20% L-Lys from L-Lys center dot HCl and 10 and 20% DDGS to the basal diets. Body weight gain was regressed on Lys intake from L-Lys center dot HCl and DDGS, and the ratio of the slopes indicated the relative bioavailable Lys in DDGS. The values as a percentage of total Lys (0.83) in DDGS yielded availability estimates of 80% for experiment 2 and 100% for experiment 3. In experiments 4 and 5, a P-deficient basal diet containing 0.12% nonphytate P was formulated. A linear growth and tibia bone ash (%) response (P < 0.05) were observed from the addition of 0.05 and 0.10% P from K2HPO4 and 2 levels of DDGS (5 and 10% for experiment 4 and 7 and 14% for experiment 5). Tibia bone ash (%) was regressed on P intake from K2HPO4 and DDGS, and the ratio of slopes indicated the relative bioavailability of P in DDGS. The values as a percentage of total P (0.74%) in DDGS yielded availability estimates of 68% for experiment 4 and 54% for experiment 5.