Two experiments were conducted to determine nitrogen-corrected true metabolizable energy (TMEn) and standardized amino acid (AA) digestibility in 4 new soybean (SB) lines varying in trypsin inhibitor. Two of the 4 SB (HBK-WF and HBK-PF) were developed by crossing a beta conglycinin alpha subunit mutant (allergen) SB and a KTi-3 mutant SB. The other 2 lines were a KTi-3 mutant (LG17), and a BBi mutant (ZB 168-1). All 4 samples of SB were autoclaved for 25 min to reduce antinutritional factors. Raw uncooked HBK-WF and HBK-PF SB contained 30 trypsin inhibitor units (TIU) per mg of sample. The raw LG17 and ZB168-1 SB contained 48 and 43 TIU/mg, respectively. Autoclaving reduced TIU of HBK-WF and HBK-PF to less than 1 TIU/mg and reduced TIU to 3 and 16 TIU/mg for LG-17 and ZB168-1, respectively. Two precision-fed rooster assays were conducted to determine TMEn in conventional roosters and standardized AA digestibility in cecectomized roosters. For both experiments, 20 individually caged White Leghorn roosters were fasted for 26 hours, then crop-intubated with 25 g of each autoclaved SB (5 roosters per sample) and excreta were collected 48 hours post-feeding. The excreta samples were analyzed for gross energy, AA, and nitrogen. Data were analyzed as a one-way ANOVA for a completely randomized design with each individually caged rooster as the experimental unit. Differences among treatment means were considered significant at (P < 0.05) using the least significant difference test. The TMEn values ranged from 2.761 to 3.069 kcal/g DM among the autoclaved SB. The TMEn was greater (P < 0.05) for HBK-PF than LG17 and ZB 168-1 SB, with HBK-WF being intermediate. Results from Experiment 2 showed that HBK-PF and HBK-WF SB had higher (P < 0.05) digestibility of AA than LG17 and ZB 168-1. Digestibility of AA in LG17 was also higher (P < 0.05) than in ZB 168-1. The results of this study indicated that reducing trypsin inhibitors in SB by genetic selection can increase TMEn and digestibility of AA in SB for poultry.
Rosales, S., P. Utterback, W. Kim, S. Kim, H. Krishnan and C. Parsons. 2025. Determination of TMEn, standardized amino acid digestibility and trypsin inhibitor activity in new reduced trypsin inhibitor varieties of soybeans. 2025 Poultry Science Association Annual Meeting, Abstract 468P