Using Soy to Feed Fish

Soybeans are one of the world’s best non-fish sources of essential omega-3 fatty acids, healthy proteins, and unsaturated fats.

High-quality soy protein is fed to farmed fish and shellfish to support growth and healthy development.

Soybean meal, soy protein concentrates, soybean oil, and other vegetable proteins and oils, can replace from one-third to one-half of the fishmeal in feeds for many farmed species, reducing the need for wild-caught fish for fishmeal.

Soybean meal costs significantly less than most animal meals, including fish meal. Reducing feed cost is critical to improving efficiency and maintaining sustainability in aquaculture operations. Because the nutrient requirements of farmed fish and shellfish are so complex, each feed ratio is formulated based on the individual species’ needs. Most farm-raised fish and shellfish can easily digest soymeal, which helps the fish more efficiently transform ingested protein into body weight.

Soy: The Sustainable Alternative

U.S. soybeans increase the affordability and sustainability of the world’s supply of healthy, farm-raised seafood, and specially formulated soy-based feeds are rich in the proteins and nutrients that support healthy and efficient fish growth while producing less waste.

Regal Springs’ tilapia farm in Honduras is a good example of a modern aquaculture success story. The fish are raised from hatch to harvest with sustainable soy-based feed, and then processed with every part of the fish utilized with no waste. This is the first farm to be certified sustainable by the Aquaculture Stewardship Council, meeting stringent standards for healthful fish, environmental impact, and community support.

The U.S. soy industry promotes environmentally friendly aquaculture production techniques around the world. Unlike wild resources for fishmeal, the soy industry can scale up to sustain the growth of global aquaculture.

Soybean Meal

Newly harvested, high-quality soybeans are the first step in soy product processing. The soybeans go through a series of cleaning, cracking, and dehulling processes followed by oil extraction for cooking, biodiesel and other uses. The residue, consisting of defatted white soy flakes, is then toasted and ground to produce the soybean meal that has become a staple in animal feeds worldwide.
 

Soybean meal
Soybean meal.

Dehulled soybean meal, with a protein content of 47%-48%, can be the primary protein ingredient in most freshwater omnivorous fish diets and a significant component of the protein composition in many marine fish and shrimp diets. Dehulled soybean meal can be routinely incorporated into all-plant protein, freshwater fish feeds at 50%-55% inclusion rates. In marine fish and shrimp diets the high nutrient density of the feeds typically limits dehulled soybean meal inclusion to a maximum rate of 30%-35%. Inclusion rates are lower for some marine species that have demonstrated an allergic response to soybean meal.

Soy Protein Concentrate

Soy protein concentrate (SPC) is made by treating the white soy flakes produced for soybean meal to aqueous alcohol extraction. The extraction process removes the soluble carbohydrate and significantly lowers the levels of lectins, trypsin inhibitors, glycinin, B-conglycinin, saponins, and oligosaccharides which are considered to be anti-nutritional factors (ANF) in regular soybean meal and also documented to have negative effects in some fish species such as gastrointestinal disturbances, intestinal damage, and increased disease susceptibility. The resulting traditional soy protein concentrate is then thermally processed to further reduce ANFs and produce low-antigen, feed-grade SPC.
 

Soy protein concentrate
Soy protein concentrate.

Low-antigen SPC has nutritional qualities that make it ideal for use in nutrient-dense aquafeeds for marine fish species, marine shrimp, and for fry and fingerling feeds for both freshwater and marine fish.

Research has also identified higher energy and nitrogen digestibility for SPC over soybean meal included in feed for fish.

Fermentation and other production technologies are also used to produce various forms of SPC.

Soy Oil

Soy oil is typically processed using a solvent extraction process. Direct solvent extraction, referred to as “full” pressing or prepress-solvent extraction, can separate oil from soybeans and is the most widely used method. However, mechanical extraction is often preferred by small extraction plants to remove the oil from soybeans.
 

Soy oil
Soy oil.

Soy oil is one of several lipid sources used in aquafeeds today. Soy oil is often blended with fish oil to provide a suitable combination of lipid and fatty acids and as a means to limit the requirement for fish oil that is in limited supply.

New soy oil products are being researched that may one day provide the fatty acid needs that are now met by fish oil.

Soy Lecithin

Soy lecithin is a by-product of soybean processing produced by further manufacturing of crude soy oil. Lecithin is the gummy material contained in crude vegetable oils and removed by a degumming process.

Soybeans are by far the most important source of commercial lecithin, and lecithin is the most important by-product of the soy oil processing industry because of its many applications in foods and industrial products. Soy lecithin is an excellent source of phospholipids, or phosphatides for aquafeeds. Phospholipids are the molecules that make up cell membranes.

The three main phosphatides in commercial soy lecithin are phosphatidyl choline (also called “pure” or “chemical” lecithin to distinguish it from the natural mixture), phosphatidyl ethanolamine (popularly called “cephalin”), and phosphatidyl inositols (also called inositol phosphatides). Commercial soy lecithin also typically contains roughly 30%-35% unrefined soy oil. Because it is readily available from plentiful soybean crops all over the world, it is the most economical and simplest type of lecithin to mass manufacture.

Soy Hulls

Soybean hulls are a byproduct of soybean processing for soybean oil and soybean meal. During processing, soybeans are rolled or cracked to break the whole bean into smaller pieces and the hulls are separated by an air stream. Hulls are usually toasted to destroy their urease activity and ground to the desirable particle size.
 

Soy hulls
Soy hulls separated from rolled or cracked whole carp feed soybeans are used as a fiber source in grass carp feeds.

The soybean hull is high in fiber (73%) and low in protein (9.4%). The protein is highly degradable while the cell wall is low in lignin and highly digestible.

Soy hulls are very palatable and are typically used to increase bulk in rations of fine texture. Soy hulls are not typically used in aquaculture feeds, but they are a good source of digestible fiber and have been found to be an effective fiber source for use in grass carp feeds.

Back to Aquaculture Home