Soybean meal (SBM) makes up approximately 40% of poultry diets. With recent increases in cost of this ingredient, evaluation of quality is critical. This study evaluated a total of 122 SBM samples collected from commercial feed mills, from nine different states, six different SBM suppliers, four different regions and included two separate harvest years (2019 and 2020). Samples were sent to two separate labs (University of Missouri agricultural experiment station chemical laboratories, and Eurofins) and analyzed for amino acids, digestibility factors, anti-nutritive factors and trypsin inhibitors. The model was a factorial in an 9 x 6 x 4 x 2 arrangement, consisting of nine states, six suppliers, four regions, and two harvest years where all samples were tested. The data was analyzed by ANOVA JMP PRO 15 (SAS Institute Inc, 2019) and means were separated by Tukey HSD with significance level set at P<0.05. Results showed state was significant (P<0.05) for trypsin inhibitor, protein dispersibility index (PDI), and protein solubility. While SBM supplier and region was significant for trypsin inhibitor and PDI only. For those parameters that were significant, northeastern region and states were of the highest (P<0.05) for trypsin inhibitor, PDI and protein solubility. The typical benchmark of urease activity to evaluate SBM quality was not significant for supplier, region or state. However, the coefficient of variation (CV) of urease activity ranged from 31% to 70%, further indicating this parameter to be too variable to utilize as an indicator of SBM quality. Total raffinose oligosaccharides (stachyose+raffinose+verbascose) was also analyzed and indicated a significant (P<0.05) difference for state, with samples from Mississippi being the lowest, supplier and region. Samples from the Midwest region had the highest (P<0.05) total oligosaccharides.
This study indicates the significant differences between supplier, the state in which that supplier resides and the region the soy comes from can play a role in the quality and nutritive factors.