Soybean meal (SBM) is produced using a solvent extraction process to remove the soybean oil; however, several other soybean products can be created by further processing of SBM or soybean. This research study compares nine different soybean protein ingredients that were processed from soybeans or SBM. These soybean products include two extruded soybean products (EX), two soybean products produced by thermos-mechanical (TM)
treatment; two products produced by bioconversion using fermentation or enzymes (BC), and two products produced using ethanol-water extraction (EW) of soybean meal.
These nine soybean products were tested in cornstarch-based diets together with an N-free diet for a total of ten diets. Ten ileal-cannulated barrows weighing about 30kg were fed the ten diets for six 9-d periods. The soybean protein products were analyzed and a metabolism study conducted. Study results were statistically analyzed.
The 9 soybean products contained 35.6% to 66.4% CP, 0.9% to 21.6% ether extract, and 4.4% to 8.0% acid detergent fiber. The EW soybean products were higher in CP, whereas the 2 EX soybean products were lower in CP), but higher in ether extract. Chemically available lysine ranged from 92.6% to 100% of total lysine, indicating that relatively minor lysine damage occurred during processing methods.
The apparent total tract digestibility (ATTD) of energy was lower (P < 0.05) for soybean products with greater ether extract and ADF content than SBM, and varied among soybean products. The standardized ileal digestibility (SID) did not differ (P > 0.05) among soybean products for most AA, except for lower SID of Arg, Ile, Leu, Lys, Phe, and Tyr (P < 0.05) for EX2 and BC1 compared to the other soybean products. The DE and predicted NE value did not differ (P > 0.05) among soybean products. The greater SID AA content (P < 0.05) in EW, BC, and TM1 soybean products compared to SBM was mainly a result of greater total AA content due to removal of other macronutrients.
In conclusion, extrusion of soybean creates soybean products with a greater energy value but lower SID AA compared to SBM. Further processing of SBM creates soybean products with greater CP and AA content compared to SBM. Thus, new technologies are available to further process SBM or soybean and will create high-value ingredients that can be included in swine rations, especially for young pigs with high nutritional requirements.
What can we learn from this study? Soybean and SBM can be further processed into value-added products, but the composition of these soybean products is variable and to make maximum use of these further-processed soybean products in swine rations accurate characterization of the digestible amino acid profile and energy value are required.