Soybeanmeal is used in food and animal feeds, principally as a protein supplement, but also as a source of metabolizable energy. Typically 1 bushel of soybeans yields 48 lbs. of soybean meal. Some, but not all, soybean meal is produced from the residue left after oil extraction. Removal of the oil, which is used mostly in food, but also for industrial oils, soaps and biodiesel, involves crushing and either pressing or solvent extraction. Some, but not all, soybean meal contains ground soybean hulls. Soybean meal is heat-treated during production, to denature the trypsin inhibitors of soybeans, which would otherwise interfere with protein digestion.
Globally, about 98 percent of soybean meal is used as animal feed. Of the US soybean production magnitude from 2010 through 2012, about 44 percent was exported as soybeans, and 53 percent was crushed in the US. Of the crushed tonnage, 19 percent was recovered as soybean oil and the remainder was recovered as soybean meal. Of the total US soybean tonnage produced, about 35 percent was fed to US livestock and poultry as soybean meal. Most of the remaining soybean meal produced in the US was exported. It has been estimated that, of soy meal fed to animals in the US, 48 percent is fed to poultry, 26 percent to swine, 12 percent to beef cattle, 9 percent to dairy cattle, 3 percent is used in fish feed and about 2 percent in pet food. Although this implies that the tonnage of soybean meal fed to other species is relatively minor, such use is not unimportant. For example, for rapidly growing lambs on low-protein feeds, soybean meal can be an important supplement to ensure adequate protein intake, and partly because of its palatability, soybean meal is often recommended for use in starter rations when creep feeding lambs.
Globally, about 2 percent of soybean meal is used for soy flour and other products for human consumption. Soy flour “provides the basis for some soy milks and vegetable protein”, and is marketed as full-fat, low-fat, defatted and lecithinated types.
Phytoestrogens
Most studies of phytoestrogens in soy have identified the isoflavonesgenistein and daidzein as its principal phytoestrogenic substances. For several soy flour samples analyzed by various persons using high-performance liquid chromatography, daidzein content ranged from 226 to 2100 micrograms per gram, and genistein content ranged from 478 to 1123 micrograms per gram. For four analyses of defatted soy meal, the concentrations were 616 and 753 micrograms per gram, respectively; for one analysis of soybean meal, concentrations were 706 and 1000 micrograms per gram, respectively. Although reproductive physiology of sheep is particularly sensitive to phytoestrogens, soybean meal supplementation of ewe lambs or ewes on pasture in some studies has been found to have no detrimental effect on reproductive performance.
