Variation in Soybean Meal Quality Measurements

Two experiments were conducted to evaluate the effects of low-oligosaccharide soybean meal (LO-SBM) on AMEn and amino acid (AA) digestibility from 28 to 32 d of age. Prior to experimentation, conventional soybean meal (CSBM) and LO-SBM were analyzed (see table):



Methods used by the soybean industry to estimate protein quality of soybean meal (SBM) include KOH solubility (KOHsol), protein dispersibility index (PDI), urease activity (UA), and trypsin inhibitor activity (TIA). In general, meals with KOHsol values between 78 and 85%, PDI values between 15% and 35%, and UA values between 0.00 and 0.10 mg/g are considered of acceptable quality. Similarly, TIA values of less than 2.5–4.0 mg/g are considered best. However, there is no agreement among the different institutions and publications with respect to the more suitable values for these variables in commercial SBM. The reasons for the wide range of values for these variables are not well understood. It is known that protein solubility and TIA changes with the methodology used would explain in part the high variability existing among laboratories. Also, length and environmental conditions during storage might influence protein solubility and thus, KOHsol and PDI values.

Spanish researchers reported observing that protein solubility of SBM samples from the USA or Latin America stored for 24, 48, and 80 wk under room conditions (12–15°C) had significantly lower PDI values than the original SBM. To confirm the observation, an experiment was conducted to determine the influence of length of storage on different parameters that define the protein quality of SBM. Eight samples (500 g) of SBM (55–56% CP on DM basis) were collected weekly during June–July 2010 directly from the crusher (USA). Samples were analyzed at arrival to the Spanish port and then, every 30 d of storage at 12 ± 2°C and 70 ± 3% humidity. Length of storage did not affect KOHsol, UA, or TIA values. However, PDI values decreased with time (21.8, 21.4, 20.1, 18.7, and 17.7% for 0, 30, 60, 90, and 120 d, respectively; P <= 0.001). Therefore, the research group concluded that care should be taken when comparing PDI values to evaluate the protein quality of SBM samples that have been stored for different lengths of time.

Sueirol, S. and co-workers. 2011. Influence of length of storage on parameters used to measure the quality of soybean meal. J. Anim. Sci. Vol. 89, E-Suppl. 1/J. Dairy Sci. Vol. 94, E-Suppl. 1; abstract 260, page 249.