Trypsin inhibitor (TI) is a significant antinutritional factor in soybean products, as elevated trypsin inhibitor activity (TIA) can hinder nutrient digestibility and contribute to gut health challenges in poultry by binding to trypsin and obstructing its digestive functions. Effectively managing TIA in soybean products and complete feed is crucial for optimizing growth and production in poultry. This study compares four analytical methods for measuring TIA, including two wet chemistry, a near-infrared (NIR) spectroscopy technique and Urease Index as indicator of under-processing of soybean products to aid nutritionists in interpreting results and correlating them with poultry performance. A total of 27 soybean samples were collected, comprising 13 mechanical-extracted soybean meal, 2 raw soybeans, and 12 solvent-extracted soybean meal samples sourced from the US and Canada. The samples were analyzed using two wet chemistry methods (AOCS Ba 12a-2020 and USDA-ARS rapid method) and NIR prediction (AMINONIR® RED, Evonik Operations GmbH). 21 out of the 27 samples underwent Urease Index analysis (pH increase). Multivariate analysis using JMP 17 was employed to assess correlations among the results from each method. The findings revealed strong correlations (P < 0.05) among NIR prediction, AOCS Ba 12a-2020, and the USDA-ARS rapid method, with R square values of 0.95 between NIR and both AOCS and USDA-ARS methods, and an R square of 0.99 between AOCS and USDA-ARS. In contrast, no significant correlations (P > 0.05) were observed between the Urease Index and the other analytical methods. These results suggest that NIR prediction via AMINONIR^® RED is a viable alternative for assessing TIA in soybean products, providing poultry producers with timely monitoring capabilities. Conversely, the Urease Index may not accurately represent TIA levels in soybean products.

Wen, J.,  S. Kim and H. Krishnan. 2025. Comparison of Analytical Methods for Measuring Trypsin Inhibitor Activity in Soybean Products. 2025 Poultry Science Association Annual Meeting, Abstract 454P