SOYBEAN MEAL UTILIZATION
By Species
Total soybean meal use in the U.S. is estimated to be 27 million
tons in 1996-7 (44). Soybean meal accounts for more than 92% of the
total oilseed meal usage in animal and poultry feeds (45). Soybean meal
is the most economical quality protein available to the feed manufacturer,
thus, soybean meals dominant role.
Approximately 85% of the soybean meal in the U.S. is fed to non-ruminants (Figure 1). The available amino acid levels in soybean meal complements those of cereal grains in meeting the nutrient requirements of poultry and swine. There is a wealth of information available that in nutritionally balanced diets, performance of non-ruminants is not improved by adding animal protein. The amino acid patterns of soybean products are balanced without excess or major deficiencies.
Essentially all poultry rations formulated in the U.S. make maximum use of soybean meal. Some animal protein may be used, especially if phosphorus ingredients are expensive. Cottonseed and peanut meals are used only if their cost per unit protein is significantly lower than soybean meal. Probably no other protein source has been so thoroughly researched as soy protein. Soybean meal is the standard to which all other protein sources are compared. The acceptance and reputation of soybean meal are widely known. There has been a lot of research has been completed trying to replace some of the soybean meal in various rations with minor protein sources (46). The results of these studies only confirm the dominate role of soybean meal and prove the replacement of soybean meal is justified only when the cost definitely favors the minor protein source.
In dairy rations, soybean meal is highly palatable and digestible, and it assists the dairyman in obtaining the highest milk yield possible from his herd. In beef cattle rations, soybean meal is one of the most respected oilseed meals. However, soybean meal must compete with urea and by-product meals and high fiber oilseed meals in ruminant markets. Where a high-quality protein source is essential, the economics of supply and demand usually favor those crude protein sources not suitable for use in poultry and swine feeds.
Soybean protein products may be used in dairy calf milk replacers with acceptable results (42-44). Research has demonstrated that soy protein products have a definite role in young calf nutrition.
Large quantities of soybean meal are used in the formulation of pet foods. Simple corn and soybean meal diets formulated for dogs perform equally to the complex diets using high levels of animal protein (50). Recent research at the University of Illinois (51), demonstrated that soybean meal replacement of poultry meal resulted in higher digestibilities of protein and starch at the ileum. They found the oligosaccharides content of the meal did not effect nutrient digestibilities. The use of soybean meal has obvious economic advantages for pet foods.
In recent years, there has been a rapid expansion of soybean meal use in aquaculture. Soy protein has one of the best amino acid profiles of all of the oilseed proteins in meeting the essential amino acid requirement of fish (52-55). Methionine and cystine have generally been identified as the most limiting. Commercial channel catfish are large users of soybean meal because their requirement for the sulfur amino acids are relatively low and soybean protein is a balanced source of amino acids in meeting the amino acid requirement of this species. Several studies have shown that heating destroys the trypsin inhibitors and improves the utilization of soybean meal (43,52). With the short supply and high prices for fish meal, it is anticipated that greater amounts of soybean meal will be used in aquaculture diets.
Research by Farley and co-workers (56) determined the digestibility of soybean meal in four mature pony geldings that were fitted with ileal cannulas. They reported that the total tract digestion of nitrogen was 95.7% and true digestion of nitrogen reaching the large intestine was 89.8%. The data indicates that the protein in soybean meal is almost completely digested in the equine digestive track. Approximately 75% of the protein was digested prececally when the nitrogen intake was less than approximately 125 mg/kg of body weight per feeding.
