Soybean meal: properties, composition and applications

Soybean meal is a product obtained by extracting vegetable oil from pre-treated soybean seeds using organic solvents. It is one of the most valuable and widely demanded sources of plant protein in global livestock farming. Due to its optimal amino acid profile, high protein digestibility and affordable price, soybean meal is recognised as a strategic component of compound feeds for all types of farm animals and poultry.

Chemical Composition and Nutritional Value

The nutritional value of soybean meal is determined by its high content of crude protein and a favourable set of essential amino acids. According to the requirements of GOST 12220-96, the mass fraction of crude protein calculated on an absolutely dry basis must be at least 45.0%, and the mass fraction of crude fibre in the defatted product — not more than 7.0%. The more recent standard GOST R 53799-2010 differentiates meal by category: basic (at least 42.0% protein), standard (at least 50.0%) and high-protein (at least 54.0%).

The crude fat content in soybean meal typically ranges from 0.5 to 4.0% depending on the extraction method and additional lipid enrichment. The total energy value is at least 1.18 feed units per kilogram of dry matter. Soybean meal is rich in B vitamins and vitamin E, and also contains potassium, phosphorus, calcium, iron, manganese and zinc.

In terms of biological value, soy protein is close to fish meal and surpasses most other plant meals in lysine content — the key limiting amino acid for pigs and poultry. The digestibility of amino acids in soybean meal in pigs exceeds 85–90%.

Regulatory Framework and Safety Indicators

Requirements for feed soybean meal in Russia and CIS countries are regulated by GOST 12220-96 "Feed soybean meal, toasted. Specifications" and GOST R 53799-2010. The standards establish requirements for organoleptic indicators (colour from light yellow to light brown, odour typical of soybean meal without foreign odours), mass fraction of moisture and volatile substances (8.5–10.0%), and ash insoluble in hydrochloric acid (not more than 1.5%).

A key safety indicator is urease activity — an enzyme that characterises the degree of heat treatment. For quality toasted meal, it must be in the range of 0.1–0.2 pH change units per 30 minutes. Too high urease activity indicates insufficient thermal treatment and the presence of anti-nutritional factors; too low — overheating and loss of lysine availability.

The standards also standardise the content of mycotoxins (aflatoxin B1 — not more than 0.025 mg/kg, T-2 toxin — not more than 0.1 mg/kg, zearalenone — not more than 1.0 mg/kg), toxic elements (lead — not more than 0.5 mg/kg, cadmium — not more than 0.1 mg/kg, mercury — not more than 0.02 mg/kg), nitrates (not more than 450 mg/kg) and nitrites (not more than 10 mg/kg). The residual amount of solvent (gasoline) must not exceed 0.1%.

Production Technology and Toasting

Soybean meal is obtained by prepressing-extraction or direct extraction schemes from pre-treated soybean seeds. During extraction, the bulk of the oil is removed, and protein is concentrated in the residue. However, raw soybean meal contains anti-nutritional substances — trypsin inhibitors, urease and other factors that block protein absorption and negatively affect animal digestion.

To eliminate these factors, soybean meal is subjected to toasting — moisture-heat treatment at temperature and humidity (15–25%) that inactivate trypsin inhibitors and denature anti-nutritional proteins, maximally increasing the nutritional value of the product. That is why in feeding monogastric animals (pigs and poultry), only toasted soybean meal is allowed.

Feeding Rates

Soybean meal is suitable for feeding all types of farm animals, but inclusion rates vary depending on the species, age and physiological state.

Cattle. Soybean meal can be added to the rations of cows and fattening cattle up to 2–2.5 kg per head per day. For adult animals and young stock over 12 months, the inclusion rate in feed mixtures can reach 20–25%. For dairy cows, soybean meal increases milk yield and improves milk quality.

Pigs. Soybean meal is the most preferred protein source for pigs due to its high digestibility and lysine content. Recommended inclusion rates in compound feeds are up to 15% for adult pigs and young stock, and up to 10–13% for fattening. When using meal in high doses, synthetic methionine and cyanocobalamin (vitamin B12) must be additionally introduced to balance the ration for sulfur-containing amino acids.

Poultry. For young poultry up to 8 weeks of age, the inclusion rate is up to 17%; for adult chickens, ducks, turkeys and geese — up to 15%. For broilers in the early rearing period, inclusion up to 25% is allowed, in the middle period — up to 15%, in the finishing period — up to 12%.

Sheep and Rabbits. Adult sheep and lambs up to 4 months can be fed up to 20%; young stock over 4 months and breeding rams — up to 10%. For rabbits, the inclusion rate depends on weight and is up to 10%.

Fish. In fish feeds, soybean meal can be used depending on the species — up to 35%.

Limitations and Safety

When using soybean meal, it is important to control urease activity to guarantee sufficient inactivation of trypsin inhibitor. Insufficiently toasted meal reduces protein digestibility and can cause digestive disorders in young animals. Overheated meal, on the contrary, loses lysine availability, which reduces its feed value.

During storage, soybean meal must be protected from moisture, as high humidity creates conditions for mould development and mycotoxin accumulation. The storage period of bulk meal is 4 months; in packaging — in accordance with the manufacturer's guarantees.

Conclusion

Soybean meal remains the main source of plant protein in global livestock farming due to its high nutritional value, optimal amino acid profile and economic efficiency. Compliance with toasting requirements, control of urease activity and balancing rations for methionine and vitamin B12 allow the potential of this component to be fully realised. Organising supplies of soybean meal, including selection of the category by protein content, quality confirmation and logistics, requires an individual approach.