Protein is a critical nutrient in the diets of food-producing animals. It provides amino acids to tissues for cellular structure and function (e.g., muscle is about 20% protein) and can be used as an energy source. Thus, it is vital for maintenance, growth, and production by animals. Crude protein (CP) generally consists of 12 to 20% of the diets for food-producing animals, depending on age and productive stage of the animal, with 16% being a typical concentration. For ruminants, the protein is supplied via concentrates and forages, but for non-ruminants, the protein is primarily supplied by grains. Soybean products are by far the most abundant source of supplemental protein in diets for food animals in the US. Of the soybeans produced in the US, about 97% are processed for animal feed, biofuels and vegetable oil; 2.6% is directly used for animal feed; and 0.1% used directly for human food. The primary ingredient for supplemental protein in farm animal diets is soybean meal (SBM). The oil is extracted either by solvent or mechanically, with about 99% of the SBM available being from solvent extraction because the solvent process results in a higher recovery of the oil than mechanical extraction. Solvent extracted SBM will have about 1.5% residual oil versus 5 to 7% with mechanically extracted SBM. Solvent extracted SBM typically contains 48% (CP, as-fed basis) if the hulls are left out during processing or 44% CP if the hulls are added back into the meal. Soybean hulls can be purchased as a separate commodity, but they only contain about 14% CP. Mechanically processed SBM is priced higher because of the residual oil for energy and the higher level of rumen undegradable protein (RUP) in comparison to solvent extracted SBM.
There is growing interest in feeding full-fat soybeans (SB) to food animals, especially to lactating dairy cattle for the energy and protein. Typical SB contain about 48% of the fatty acids (FA) as linoleic acid (C18:2) and 25% as oleic acid (C18:1). In the new variety of high oleic acid Plenish SB, C18:2 is at about 6% and C18:1 at 74% (Bales and Lock, 2024). The lower level of unsaturation results in lower risks to disrupting ruminal fermentation. Heat treating both types of SB has interest to reduce the antinutritional properties and increase the level RUP in the SB, whereby more of the protein is degraded in the small intestine instead of in the rumen. Therefore, the goal is to adequately heat the SB to reduce the antinutritional properties but not overheat the protein source whereby the total tract digestibility of the protein is reduced. The heat processing (roasting) may be done at a feed plant or on-farm. In either case, the temperature used in the roasting, steeping time, and cooling mechanisms post-roasting are critical for optimal results. Thus, various options for assessment of protein quality in SBM and full-fat SB are described in Table 1. Several commercial laboratories offer these analytical methods.
Source : osu.edu