Soybeans remain the most efficient source of oil, and the animal industry continues to enjoy soybeans as a primary source of protein in the form of soybean meal — the by-product of oil extraction. Nevertheless, diets for young pigs and calves, and even broilers, cannot fully utilize normal soybean meal as it contains a plethora of anti-nutritional factors that are not completely eliminated. More concentrated forms of soybean protein are available, derived either from whole soybeans or from further processing of soybean meal. Besides that, it merits understanding their method of production and market position in order to fully comprehend the soy protein industry and the uses of these ingredients.
Soy protein concentrate
Soy protein concentrate (SPC) is the most common soy protein used in diets for young animals. It contains about 65 percent crude protein and is derived from water/ethanol extraction from white soybean flakes. As such, it is very low in heat-stable and heat-sensitive anti-nutritional factors. In fact, the water extraction process reduces the antigenicity of soy proteins, a problem associated with digestive immune hypersensitivity distinct from that caused by anti-nutritional factors. It is considered the reference protein source in terms of pricing for other vegetable purified proteins, such as wheat gluten, pea protein and potato protein. In market terms, SPC is considered today a commodity.
Soy protein isolate
Soy protein isolate (SPI) is an even more concentrated form of soy protein, containing about 80 percent crude protein, but it does not include the water extraction process. As such, the antigenicity problems persist, even though the presence of anti-nutritional factors is virtually zero. This ingredient is used extensively in human nutritional supplements, a fact that keeps its price quite elevated — on a protein basis. Nevertheless, substantial quantities of lesser quality SPI are widely available and frequently flood certain markets. High quality SPI is ideal for milk replacers for newly born pigs and ruminants and can replace other more expensive protein sources. In market terms, SPI is a rather rare ingredient.
Fermented soybean meal
Unlike SPC and SPI, fermented soybean meal (FSM) is derived using soybean meal instead of whole soybeans. It has a lower protein concentration (about 55 percent) and a higher level of anti-nutritional factors, especially non-starch polysaccharides. The latter are frequently associated with diarrhea in young animals, when included above a certain level in their diets. Fermentation is achieved using yeast that consumes carbohydrates and converts plant protein into yeast protein — presumably of higher quality. If done correctly, FSM can replace normal fishmeal, as evidenced by certain preliminary trials. In market terms, FSM is considered today an emerging product that is still brand-specific, as the technology of its production differs among manufacturers.
Microbial soybean meal
Instead of fermenting soybean meal with yeast, it is also possible to do the same using a microbial culture. Microbes are already used in our industry to produce medicines, amino acids and other specific compounds. The specific technology that uses soybean meal is proprietary knowledge. The resulting product is similar to fermented soybean meal (55 percent crude protein), although it appears lower in anti-nutritional factors — depending on the fermentation process followed for FSM. As both ingredients are derived from soybean meal, they are richer in non-starch polysaccharides and still pose the risk of antigenicity compared to soy protein concentrate. In market terms, microbial soybean meal (MSB) is a unique product that competes with fermented soybean meal in price, usage and efficacy. Both ingredients are suitable replacements for normal fishmeal.
Research has demonstrated a direct relationship of trypsin inhibitor activity daily intake to animal performance.
Trypsin inhibitor activity, or TIA (mg/kg) is the internationally accepted index analysis that determines the quality of any soy product in regards to anti-nutritional factors. Although the latter encompass a great number of dissimilar compounds, TIA has been shown to be a good representative of all. In fact, well-documented research has demonstrated a direct relationship of TIA daily intake to animal performance (see figure). As such, it is possible to use products of different TIA concentration at different dietary inclusion levels without affecting animal performance. Tests that measure protein quality are also important, as they are for soybean meal used in diets for older animals, but these tests do not tell anything about anti-nutritional factors.
In most cases, testing SPC and SPI for TIA is enough to make a business decision regarding the overall quality of these ingredients. In contrast, FSM and MSB require protein and TIA tests to assess their overall quality.