Chemical composition and nutritional quality of soybean meals prepared by extruder/expeller processing for use in poultry diets.

This research examined variation in chemical composition and nutrient quality of soybeans (SBs) and soybean meals (SBMs) produced at seven commercial extruder/expeller plants in the United States (experiment 1), as well as differences in amino acid digestibilities when roosters were fed SBMs extruded at 121, 135, 150, or 160 degrees C at a U.S. pilot processing plant (experiment 2). In experiment 1, limited variation existed in the composition of SBs arriving at the plants, whereas substantial differences were noted in amino acid composition and protein quality of the resultant SBMs. In experiment 2, the SBMs extruded at 121 and 135 degrees C were underprocessed as noted by high urease activities and lower amino acid digestibilities. Soybean meals extruded at 150 and 160 degrees C resulted in higher amino acid digestibilities and lower urease activities, indicating adequate processing. Large variation exists in the nutritional quality of extruder/expeller SBMs currently in the marketplace. Optimal processing temperatures should be >135 degrees C, and temperatures as high as 165 degrees C do not result in overprocessing.

Chemical and nutritional characteristics of United States soybeans and soybean meals.

Two experiments were conducted to determine U.S. soybean meal (SBM) variation. In experiment 1, SBM from 55 U.S. processors was evaluated. Significant (P < 0.05) but numerically small differences were detected in dry matter (DM) and organic matter (OM) concentrations. Crude protein (CP) concentrations (51.6-54.6%) were higher (P < 0.05) in SBM produced in the southern U.S. Lipid and total dietary fiber concentrations also differed (P < 0.05). The protein dispersibility index was affected (P < 0.05) by the source of SBM. In experiment 2, soybeans and resultant SBMs were obtained from 10 U.S. processing plants. Soybean DM, OM, and CP concentrations differed (P < 0.05). Soybean meal varied (P < 0.05) in CP (48.2-56.2%), acid-hydrolyzed fat (3.3-9.2%), total dietary fiber (17.0-20.7%), and lysine concentrations. Soybean meal carbohydrate composition was also affected by processing conditions. These results indicate a significant variation in chemical and nutritional characteristics of U.S. SBM from different sources.