Soybean is one of the most utilized crops in the world. It is highly utilized in various forms and industries, ranging from the food manufacturing industry to the livestock feed industry. Soybean is a leguminous crop that is very high in protein.

Soybean is a good source of protein in livestock diets; it has a good profile of essential amino acids needed for plant growth. Soybean contains crude protein of about 35 – 40%, which is relatively a high quantity and very palatable for livestock. As good as soybeans are, they contain anti-nutritional factors of Antinutrients

What are Anti-nutritional factors?

Antinutritional factors (ANFs) are compounds present in food items that tend to reduce the availability of nutrients present in the food item. Anti-nutritional factors are present in oil seeds, like soybeans, cotton, and groundnut.

The anti-nutritional factors in soybeans are quite surplus; they are toxic, stimulatory, and inhibitory. They are known to have detrimental effects on the digestibility and utilization of proteins. These compounds render the beneficial nutrients in soybeans unavailable.

When raw soybean is used in animal feed formulation, the anti-nutritional factors tend to reduce the quality of the protein present in the soybean, thereby reducing the quality and efficiency of the feed. For the best usage of soybean, it must be treated to eliminate the anti-nutritional factors present in it.

The Anti-nutritional factors in soybean are:

• Trypsin inhibitors
• Lectins
• Phytoestrogen
• Tannin
• Saponin
• Oligosaccharides
• Phytic acid

1. Trypsin inhibitors

Trypsin inhibitors are specific proteins present in raw soybeans; they inhibit protease enzymes present in the digestive tract of the animal. Protease enzymes are responsible for the breakdown and availability of proteins.

Raw soybeans, when used in animal diets, often cause stunted growth because the proteins in the soybean cannot be successfully absorbed in the small intestine of the animal due to the inability of the enzyme, Trypsin, to act on them.

2. Lectins

Lectins are also called haemagglutinins. They are also capable of inhibiting growth like trypsin inhibitors. Lectins are compounds that agglutinate red blood cells in monogastric animals; they also damage the lining of the digestive tract.

The main effect of lectins is the damage they cause to the digestive tract of the animal, mostly monogastric. This damage results in the low digestibility of nutrients and proper functioning of the digestive tract.

3. Phytoestrogen

I know you are familiar with estrogen, a common hormone found in female animals. Phytoestrogen mimics estrogen, they are usually found in minute concentration in raw soybeans; they have little or no effect on the performance of animals when fed.

4. Tannins

Tannins are phenolic compounds present in soybeans. They are also in little concentration which is not of significant importance in animal feed formulation.

5. Saponins

Soybean contains a small concentration of saponins. Saponin is a compound known for its ability to impart a bitter taste in soybeans and any feedstuff they are found. They are also of little or no effect on the performance of animals.

6. Oligosaccharide

Oligosaccharides are types of carbohydrates that cannot be digested by monogastric animals. In humans, they cause flatulence, which is the release of gases, as a result of the microorganisms in the large intestine feeding on them. Oligosaccharides are indigestible, hence, reducing the energy content to be supplied by soybean.

7. Phytic acids

Lastly, Phytic acids are present in all plants. Soybean contains about 1.5% of Phytic acids; they resist the digestion of phosphorus present in the soybean. This leads to the deficiency of the mineral if soybean is its primary source in that particular diet.

They also distort the absorption of other essential minerals like calcium, zinc, and iron; in the digestive tract. To curb the effect of these acids and aid the effective utilization and absorption of phosphorus and other essential minerals in the diet, an enzyme called Phytase is added to the diet. It neutralizes the effects of these acids and aids the availability of the minerals.

How To Eliminate Anti-Nutritional Factors In Soybean

Soybeans are essential in animal nutrition. It is a good source of protein with a good amino acid profile. The detrimental effects of these antinutrients often result in the poor utilization of soybeans by livestock.

However, these anti-nutritional factors can be eliminated before using soybean as a feed ingredient. There are different methods of eliminating antinutrients present in soybeans; these methods result in the production of full-fat soybean and soybean meal.

Primarily, these anti-nutritional factors are removed through heat application. Heat denatures antinutrients, therefore all the methods used in treating soybeans are through the application of heat through various means and concentrations. These methods are:

• Roasting
• Extrusion

1. Roasting

Roasting involves exposing the soybean to a high temperature for a short time. This can be achieved through several means such as passing the soybean through a heat source in a continuous flow system or through the traditional means of roasting groundnut.

The beans can also be suspended in a stream of hot air. After roasting, the soybean should be exposed to air for about 10 minutes to fully deactivate the antinutrients present in it.

2. Extrusion

Extrusion is a mechanized method of eliminating the anti-nutritional factors in soybeans. Extrusion involves the application of high pressure and temperature to soybean in a continuous screw system called a cooking extruder. The heat created through friction and pressure is used to eliminate the antinutrients present in the soybean.

Extrusion increases the quality of the soybean by increasing its surface area as the extrusion process disrupts the cell walls of the beans, thereby exposing the nutrients. Extrusion usually takes a short period compared to other methods.

Related: Common Anti-nutritional Factors in Animal Feed Ingredients

End Notes

Antinutrients are present in almost all known crops. As a livestock farmer or animal nutritionist, you must ensure soybeans are treated before being considered as a feed ingredient for livestock, particularly in chicken feed.

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