Alternative byproducts to replace soya bean in pig nutrition

Estimated reading time: 5 minutes

  • This article discusses alternative byproducts to replace soya bean in pigs’ diets and their effects on growth performance and carcass and meat quality traits.
  • Alternative byproducts used in pigs’ diets include oilseed, local plant, byproducts from industrial processes and processed animal protein.  
  • Oilseed byproducts (including meals, cakes and expellers) are derived from oil-bearing plants.
  • Minor local plants such as guar can be used as soya bean substitutes.
  • Total replacement of soya bean with rapeseed meal affects the chemical composition of different pork cuts, reducing the fat content of shoulder and steak while increasing the fat content of ham and belly; however, total soya bean replacement with rapeseed had no effect on pork stability during storage.

There is an increase in global demand for sustainable protein sources. This article discusses alternative byproducts to replace soya bean in pigs’ diets and their effects on growth performance and carcass and meat quality traits.

Factors including physical and chemical characteristics of alternative sources, level of essential amino acids, presence of anti-nutritional factors, and the conversion method into final products are essential to evaluate the potential replacement of soya bean.

Alternative byproducts used in pigs’ diets include:

  • Oilseed byproducts.
  • Local plant byproducts.
  • Byproducts from industrial processes.
  • Processed animal protein byproducts.

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Oilseed byproducts

Oilseed byproducts (including meals, cakes and expellers) are derived from oil-bearing plants. Defatted by-products from linseed and sesame contain high volumes of crude protein. Rapeseed meal obtained from the pressed cake remaining after oil extraction contains 35% protein and high fibre, 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 a low erucic acid content and glucosinolates, making it a potential candidate for soya bean replacement.

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Local plant byproducts

Minor local plants such as guar can be used as soya bean substitutes. Guar meal is a byproduct of guar gum production which contains highly viscous non-starch polysaccharides such as galactomannan polysaccharide, which enhances digesta viscosity, prevents gut enzymatic activities, and decreases nutrient digestibility.

Industrial process byproducts

Distillers’ dried grains with soluble are the main byproducts from the ethanol industry produced by dry-mill ethanol plants. Distillers’ dried grains with soluble are a proper source of protein (25 to 30% dry matter), fat, fibre, and energy for the swine diet. In addition, they are used significantly in swine diets because of the encouraged use of renewable energy sources for the production of biofuels.

Furthermore, distillers’ dried grains with soluble have well-digested protein characteristics, a 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 byproduct. Rice distillers’ byproduct is another good source of crude protein; however, the high fibre content limits its use in pig diets.

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Animal protein byproducts

The main processed animal proteins used in pig diets include:

  • Meat and bonemeal.
  • Blood products.
  • Inedible meat.
  • Waste animal tissue and fat.
  • Feather meal.
  • Poultry byproduct meals.
  • Fishmeal byproducts.

Furthermore, liquid whey residues from the cheese industry can be used as dried ingredients. Fish silage has a high protein content (39,01%), protein digestibility (93,58%) and biological value. However, due to its high moisture content, high price and limited availability, its application in swine diets has been decreased.

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Growth and carcass traits

Rapeseed meal inclusion in pig diets decreases feed intake due to the presence of glucosinolate, which reduces palatability. Different inclusion levels of rapeseed meal in the growing and finishing periods have no significant effects on average daily gain (ADG) and feed conversion ratio (FCR), demonstrating the flexibility of using this protein source alone or together with other sources.

Furthermore, rapeseed meal can be added to other legumes to replace soya bean; however, it is required to add synthetic amino acids to the mixture to balance the nutritional quality. However, there are contrasting results regarding the impact of rapeseed meal on growth performance due to differences in the glucosinolate concentrations in each variety of rapeseed.

In addition, rapeseed meal contains high amounts of anti-nutritional factors in the variety used; however, rapeseed meal inclusion has no impact on carcass traits including dressing percentage, backfat thickness, lean content, weight, carcass yield and composition of cuts.

Guar meal inclusion in pig diets decreases average daily feed intake, ADG and FCR. Defatted rice bran has negative effects on performance with an increase in feed intake and a decrease in ADG and FCR; however, it has no impact on the quality of the carcass. Supplementing fishmeal decreases daily feed intake and weight gain and FCR. In addition, fishmeal inclusion reduces backfat thickness, loin depth and fat depth.

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Effects on meat quality traits

Total replacement of soya bean with rapeseed meal affects the chemical composition of different pork cuts, reducing the fat content of shoulder and steak while increasing the fat content of ham and belly; however, total soya bean replacement with rapeseed had no effect on pork stability during storage.

Corn (maize) distiller’s dried grain with soluble has a high content of unsaturated fatty acids which negatively impact meat quality and decreases the protein content. Fava bean as a partial replacement for soya bean increases meat tenderness, juiciness and palatability; however, the flavour is not affected. The inclusion of yellow lupin in the diet causes lower odour, taste and juiciness scores. Corn distiller’s dried grain enhances the tenderness and juiciness of meat, and fishmeal silage decreases the hardness and overall acceptability of meat.

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Concluding remarks

Traditionally, soya bean is the main source of protein in pig diet formulation. However, in recent years the application of soya bean has been limited due to rising prices, ethical issues, environmental impact and competition for land use.

Various byproducts, including oilseed byproducts, local plant byproducts, byproducts from industrial processes and processed animal protein are among the potential soya bean substitutes. However, further research is required to assess cost-effectiveness and effects on meat properties. – Samaneh Azarpajouh, All About Feed

Article courtesy of All About Feed. Visit www.allaboutfeed.com for more information.

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