Evaluation of 24 commercial lots of soybean meal of different origins indicates that both KOH protein solubility and trypsin inhibitor analyses are needed to determine soybean meal quality

   

A set of 24 solvent extracted commercial soybean meal (CSBM) samples, which corresponded to the same lots of CSBM used in the field, were evaluated. The CSBM were from different origins (Argentina, Bolivia, Paraguay, Trinidad & Tobago, U.S.). The objective herein was to evaluate the relationship between KOH protein solubility (KOHPS, a measurement of overprocessing) and trypsin inhibitor activity (TIA, a measurement of underprocessing and overprocessing) and to determine if their ranges of adequacy overlap. The 24 CSBM samples were analyzed for: 1) KOHPS (Ruiz et al. 2022 IPSF Abstract M105), 2) TIA by the new official AOCS enzymatic method (Ba 12a-2020) and a NIR method (Evonik AminoNir®), and 3) in vivo amino acid (AA) digestibility determined utilizing the precision-fed cecectomized rooster bioassay as described by Corray et al. (2018. Poult. Sci. 97:3987-3991). Correlations were conducted using PROC GLM in SAS (2013) and the significance value was determined at P < 0.05. The KOHPS values ranged from 88 to 52%, while TIA ex[1]pressed as TUI/mg ranged from 12.8 to 1.0 and TIA expressed as mg trypsin inhibited (TId)/g ranged from 4.9 to 0.6 (Evonik NIR method). There was a positive correlation (P < 0.05) between the AOCS enzymatic method and the Evonik NIR method. Lysine digestibility coefficients (dLYS) ranged from 0.9602 to 0.7018 and were positively correlated with KOHPS (P < 0.05). Ruiz et al. (2022 IPSF Abstract M106) previously reported that CSBM that was adequately processed (i.e. not overprocessed) exhibited 80 to 85% KOHPS, which correlated with 0.88 dLYS coefficient or greater. Samples that exhibited 80 to 85% KOHPS herein had variable TIA. Some of these samples contained 3.5 to 5.3 TUI/mg (2.5 to 3.0 mg TId/g) and the field assessment was satisfactory; however, some of these samples contained 6.4 to 12.8 TUI/mg (3.4 to 4.9 mg TId/g), which correlated with the observation in the field of rapid feed passage and poor zootechnical performance in broilers internationally. In conclusion, KOHPS and TIA adequacy ranges overlap and consequently both measurements are necessary to adequately determine the quality of CSBM of different origins.

Key Words: Soybean meal, Trypsin inhibitor activity, Amino acid digestibility, Rapid feed passage, Overprocessing.