Grieshop, C. M., C. T. Kadzere, G. M. Clapper, E. A. Flickinger, L. L. Bauer, R. L. Frazier, and G. C. Fahey, Jr. 2003. Chemical and nutritional characteristics of United States soybeans and soybean meals. J. Agric. Food Chem. 51:7684-7691. Link to full text (.pdf)

Take-home message:

• Soybean meal produced in the northern U.S. (maturity zones 1 and 2) has lower crude protein concentration than soybean meal produced further south in the U.S.
• This difference could be due to:
  • Environmental conditions.
  • Genotypic variation.
  • Conditions employed at the processing plant.
• More variation occurred in total essential amino acids and total amino acid concentrations of soybean meal than of soybeans, perhaps because of variation in processing methods.
• Variation exists among soybean meals prepared in the U.S., but less than found in many feed ingredients.