Bioavailability of valine in spray-dried L-valine biomass is not different from that in crystalline L-valine when fed to weanling pigs

An experiment was conducted to test the hypothesis that Val from a spray dried L-Val fermentation biomass (Val-FB; 64.4% L-Val) has a bioavailability of 100% relative to Val from L-Val (98% L-Val) when fed to weanling pigs. A Val-deficient basal diet containing 0.63% standardized ileal digestible (SID) Val was formulated. Six additional diets were prepared by supplementing the basal diet with 0.08%, 0.17%, or 0.25% L-Val or 0.12%, 0.25%, or 0.37% Val-FB to create experimental diets from both Val sources that contained 0.71%, 0.79%, or 0.87% SID Val. Two hundred twenty-four weaned pigs (6.87 ? 0.64 kg initial BW) were allotted to a randomized complete block design with 7 diets, 4 pigs per pen, and 8 replicate pens per diet. Diets were fed for 20 d. At the conclusion of the experiment, a blood sample from 1 pig per pen was analyzed for blood urea nitrogen (BUN) and plasma free AA. A linear regression model was used to estimate the relative bioavailability (RBV) of Val in Val-FB relative to Val from L-Val. Results indicated that the final BW and ADG were greater (P 0.01) for pigs fed diets supplemented with Val-FB than pigs fed diets supplemented with L-Val. The ADFI decreased (linear, P 0.01), whereas G:F increased (linear, P 0.01) by increasing inclusion of both Val sources in the diets. Regardless of source of dietary Val, BUN values were reduced (linear and quadratic, P 0.01) as the concentration of Val in the diet increased. Pigs fed diets supplemented with L-Val had increased (linear and quadratic, P 0.05) concentrations of Val and Arg in plasma, and plasma concentrations of Ile, Leu, Lys, Ala, Cys, and Pro linearly increased (P 0.05). There was also an increase (linear, P 0.05) in plasma concentrations of Ile, Leu, Met, Ala, Asp, Cys, and Pro as Val-FB was added to the diets, and the concentration of Val in plasma increased (linear and quadratic, P 0.05). Using L-Val as the standard, the RBV of Val in Val-FB as determined by ADG, G:F, and final BW was 146%, 135%, and 143%, respectively, with 95% confidence intervals of 99% to 191%, 83% to 187%, and 70% to 217%, respectively. In conclusion, the linear regression estimated a RBV of at least 100% for Val in Val-FB relative to Val from L-Val, and pigs fed diet supplemented with Val-FB had greater final BW, ADG, and G:F than pigs fed diets supplemented with the same amount of Val from L-Val.