Soybean meal is the inevitable vegetable protein source for poultry, and it is the most common, widely used feed ingredient. It has also become the world-wide standard against other protein sources for comparison. Protein content varies from 44 to 48% which depends on seed variety, oil extraction processing, and harvesting time. Its amino acid profile is excellent and highly digestible, which helps in cost-efficient feed formulation for animals or birds. In addition, it is also a rich source of potassium and isoflavones. Isoflavones have been implicated in enhancing immunity and improving growth performance and carcass traits.
Soybean processing
Soybean meal is a byproduct of soya oil industry; after cracking the seed, oil is extracted at 70°C using hexane. The hexane is then removed completely by evaporative cooling; otherwise, the residual hexane may cause liver problems in birds.
This highly valued feed ingredient contains many anti nutritional factors (ANF) which is one of the most important restrictions in the use of soybeans and their products in monogastric animal diets. The presence of these factors is also the main reason why different technological treatments are applied to soybeans or their products.
Anti-nutritional factors
Following are different ANFs which are easily destroyed with proper heat treatment (except mycotoxins). First five are intrinsic, while mycotoxins are formed because of high moisture content and improper storage of the soya seed or soya doc.
1. Trypsin inhibitors: The residual trypsin inhibitor in soybean products combines with the trypsin in the small intestine and forms an inactive complex thus reducing the availability of proteins by reducing the digestibility of specific amino acids. It induces pancreatic hypertrophy causing increased secretion of trypsin (loss of endogenous nitrogen). Independent of this, trypsin inhibitors have been correlated with the occurrence of “rapid feed passage” syndrome in broilers. The combined effect on the bird is a reduction in nitrogen retention, growth, and feed conversion.
2. Antigenic compounds: Glycinin and B conglycinin are the allergens present in soya beans, which may induce inflammatory responses in the intestines.
3. Agglutinin: It is a non-fiber carbohydrate-related glycoprotein. The structure is similar to lectins found in other leguminous plants but is more stable. It causes negative effects on animal’s intestinal health by influencing the intestinal structure, barrier function, mucosal immune system, and the balance of the intestinal flora.
4. Anti-vitamin factors against vitamins A, B2, and D3.
5. NSP and OS: Soybean meals contain approximately 30% carbohydrates (DM basis), of which only a small part is in the form of starch. A significant proportion (7-10%) comprises indigestible OS (e.g. raffinose, stachyose, verbascose). Up to 20% of dry matter is in the form of NSP such as arabinogalactans and galactomannans. See details.
Source: Email/GFMM
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