There is an increase in global demand for sustainable protein sources. This article will discuss alternative by-products to replace soybean in pigs’ diets and their effects on growth performance and carcass and meat quality traits.
Factors including physical and chemical characteristics of alternative sources, the level of essential amino acids, the presence of anti-nutritional factors, and the conversion method into final products are essential to evaluate the potential replacements of soybean.
Alternative by-products used in pigs’ diets include:
Oilseed by-products (including meals, cakes, and expellers) are derived from oil-bearing plant species. Defatted by-products from linseed and sesame comprises high volumes of crude protein. Rapeseed meal obtained from the press cake remained after oil extraction contains 35% protein and high fibre content, sulphur-containing amino acids, and phosphorus. However, rapeseed meal consists of anti-nutritional factors such as glucosinolates, tannins, and phenols which limit its application in the swine diet to up to 15%. Although, the canola meal derived from a variety of rapeseed contains low content of erucic acid and glucosinolates making it a potential candidate for soybean replacement.
Minor local plants such as guar can be used as soybean substitutes. Guar meal is a by-product of guar gum production containing highly viscous non-starch polysaccharides such as galactomannan polysaccharide which enhances digesta viscosity, prevents gut enzymatic activities, and decreases nutrient digestibility.
Distillers’ dried grains with soluble are the main by-products from the ethanol industry produced by dry mill ethanol plants. Distillers’ dried grains with soluble are a proper source of protein (25-30% dry matter), fat, fibre, and energy for swine diet. In addition, they are significantly used in swine diets because of the encouraged use of renewable energy sources for production of biofuels. Furthermore, distillers’ dried grains with soluble have well-digested protein characteristics, low content of anti-nutritional substances, and high nutritional values. However, they are rich in unsaturated fatty acids which can negatively affect dietary intake and the oxidative stability of the by-product. Rice distillers’ by-product is another good source of crude protein; however, the high fibre content limits its use in pig diets.
The main processed animal proteins used in swine diets include:
Furthermore, liquid whey residues from the cheese industry can be used as dried ingredients. Fish silage has high protein content (39.01%), high protein digestibility (93.58%), and high biological value. However, due to high moisture content, high price and limited availability, its application in swine diets has been decreased.
Traditionally, soybean is the main source of protein in pig diet formulation; however, in recent years the application of soybean is limited due to rising prices, ethical issues, environmental impact, and competition for land use. Various by-products including oilseed by-products, local plants by-products, by-products from industrial processes, and processed animal protein by-products are among potential soybean substitutes. However, further research is required to assess their cost-effectiveness and effects on meat properties.
Soybean Replacement by Alternative Protein Sources in Pig Nutrition and Its Effect on Meat Quality – published on PubMed