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Variability in energy value, nutrient and trypsin inhibitor content of extruded full-fat soybeans due to genetics and agronomic conditions

Mejia-Abaunza, N., P. Lozano-Cruz, J. Cabanas-Ojeda, V. Lima Aragão Neto, M. Joseph, D. Patino, R. Vann and E. Oviedo-Rondon

Dry extruded full-fat soybean meal (FF) is used as a feed ingredient for poultry. Meal quality can vary due to processing, soybean variety, and production conditions. This study evaluated the proximate and predicted energy values, and trypsin inhibitor activity (TIA) of FF affected by soy genetics, location, and seasons in a factorial experiment. Two soybean varieties (SV), AG56X8 (X) and S62XT09 (Y) were planted in three North Carolina counties (A, B, C location) at two planting dates: double crop and full season. 12 treatments resulted from the 2x3x2 factorial arrangement. Soybeans were harvested as they reached maturity, dried to 8-8.5%, and dry-extruded between 148-154.5oC in a single screw extruder, Insta-Pro 2000R. Five samples were collected from raw soybeans and FF, ground in Retsch mill to 0.5 mm, and scanned in triplicate in NIRS. The spectra were analyzed using AminoNIR (EVONIK) calibration curves. The data was standardized to DM basis and analyzed using a three-way ANOVA with mean separation using Tukey’s test. Three-way interaction effects (P<0.001) were observed on nutrient composition. Soybean grown in full season with variety X in locations A and B produced FF with the highest crude protein (CP), compared with the double crop with the same SV in location C, which contained the lowest CP and highest ether extract (EE). However, there was a negative correlation between CP and EE. Higher crude fiber (CF) was observed in both SV in location C regardless of planting date and in SV X in the double crop at location C had the highest value. Both SVs had the highest AMEn in location B for the double crop. In this location, SV X had higher AMEn values in the full season. The AMEn was positively correlated to EE content. The SV X in locations A and B planted in full season contained the lowest TIA. Both SV in location C planted in double crop had the highest TIA values. The correlation (P<0.001) between raw soybean and FF in CP, EE, CF, and TIA were 0.86, 0.66, 0.65, and 0.58, respectively. The TIA in FF can be predicted (P<0.001) from its content in the raw soybeans (Y= -20.39+1.15X; R2 =0.34).

In conclusion, agronomic factors may influence nutrient content, TIA values, and controlling these factors may improve FF quality and re- duce variability.