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National Hog Farmer is the source for hog production, management and market news
July 18, 2019
By Jorge Y. Perez-Palencia, Tofuko A. Woyengo and Crystal L. Levesque, South Dakota State University Department of Animal Science
Aspects associated with nutrition and feeding management of pigs are the target of countless research given its importance to profitability for the pig industry. Within the nutritional strategies to reduce costs, alternative ingredients and co-products from the ethanol and biofuel industries are increasingly used in diets for pigs (Zijlstra and Beltranena, 2013). These ingredients contain important levels of protein, minerals, fiber and other nutrients. However, the high content of fiber in the form of structural carbohydrates, and antinutritional factors, which limit the ability of the pig to utilize the energy in these ingredients, affect the digestibility of other nutrients and consequently pig performance (Urriola et al., 2013; Molist et al., 2014).
Much promising research has been conducted during recent years evaluating strategies that improve the nutritional value of these co-products, including the use of various processing techniques and enzymes supplementation. However, a consensus is needed to know the effectiveness of these technologies and identify possible factors associated with their use.
The objective of this review is to summarize recent research in which feed processing methods and exogenous enzymes were applied to improve nutritional value of high-fiber feed ingredients for growing pigs.
High-fiber feed ingredients
Corn, wheat, barley, oat, sorghum and rye are the most well-known grains used as energy sources in pig diets. However, agroindustrial byproducts from cereal grain processing and coproducts from the ethanol and biofuel industries are becoming increasingly available and represent an opportunity for livestock production. The most widely utilized co-product in pig diets is distillers dried grains with solubles which is the primary coproduct from ethanol production and the coproduct with the greatest understanding of how to optimize its use without compromising performance or carcass quality. Coproducts from wheat flour milling industry, such as the wheat bran, contain higher dietary fiber than wheat but an important concentration of nutrients. Canola meal is a coproduct derived after oil extraction processing and has become an attractive feedstuff for pigs due to their increased availability. Other interesting coproducts such as high-protein canola meal and cold-pressed canola cake have emerged (Seneviratne et al, 2011; She et al, 2017). Coproducts from the copra and palm kernel industries (copra meal, copra expellers, palm kernel meal and palm kernel expellers), the rice industry (rice bran and brown rice), rapeseed meal, camelina meal and cold-pressed camelina cake (Stein et al, 2015; Adhikari et al, 2016a; Bournazel et al, 2018; Woyengo et al, 2018) are increasing in availability. Strategies to improve utilization of the inherent fiber content and limit concentration of other antinutritional factors will be important to fully optimize use of these coproducts in swine diets.
Feed processing can be used to improve nutrient digestibility and pig performance. Through these technologies, the cellulose and hemicellulose fractions are partly solubilized and antinutritional factors are eliminated (Kerr and Shurson, 2013). Within the main forms of processing, changes in grinding procedures, expansion, extrusion, pelleting, use of enzymes and chemical treatments have been researched and discussed in non-ruminant’s nutrition (Rojas and Stein, 2017).
Extrusion consists of the combination of high pressure with high temperatures, which results in the increase of energy and nutrient digestibility in cereal grains (Hancock and Behnke, 2001). According to the articles found, extrusion had positive effects on nutrients digestibility of cold-pressed soybean cake but did not improve digestibility of hemp hulls (Woyengo et al, 2016; Kin et al, 2018). Furthermore, the hydrothermal acid treatment (acid extrusion) had minimal effects on corn DDGS (Vries et al, 2014). The fermentation of high-fiber ingredients before use in the diets can promote hydrolysis of fiber and improve the use of nutrients. Moreover, steeping feedstuffs in combination with exogenous fiber-degrading enzymes may have an increased effect in improving feeding value of fibrous ingredients in liquid feeding systems. However, not all studies reported positive results of these processing method (Jakobsen et al, 2015; Rho et al, 2018a; Rho et al, 2018b). According to Rho et al. (2018b), fermentation is a complex process where factors such as temperature, dose and type of enzyme, substrate and duration of fermentation can cause variations in results.
Other common processing methods that have been poorly studied in high-fiber ingredients for pigs have an interesting potential to improve the nutritive value of fibrous feedstuffs. For example, pelleting combines heat, moisture and pressure for agglomerate small feed particles after grinding and seems to have important effects on nutrients digestibility as evidenced by Yang et al. (2017). The processing conditions (a nonheated and heated barrel at slow and fast screw speed) during cold-pressed canola cake production also may have some effect on chemical characteristics and nutritional quality of the final product (Seneviratne et al, 2011).
The use of exogenous enzymes in pig diets is a nutritional strategy widely used and seeks to improve nutrient digestion, especially when fibrous ingredients are used because these ingredients have high concentrations of β-glucans and arabinoxylans. The most commonly used enzymes are β-glucanases, xylanases and phytase; these enzymes are used individually or in the form of multi-enzyme complexes also called enzyme blends (Emiola et al, 2009; Willamil et al, 2012; Woyengo et al, 2018).
The inclusion of phytase in diets containing high fiber feed ingredients may improve calcium and phosphorus digestibility, reduce the excretion of these nutrients and allows adjusting the inclusion of mineral sources in the formulations. The effectiveness of exogenous phytase to improve the digestibility of phosphorus and calcium and reduce the concentration of phosphorus in feces has been clearly demonstrated when included between 500 and 2,500 FTU/kg diet. Superdosing phytase (>2,000 FTU/kg) in first phases of nursery pig diets is increasingly used as a means to enhance young pig performance. Xylanase inclusion (4,000 to 24,000 units/kg feed) improved nutritional value of high fiber feed ingredients in 50% of the studies, while β-mannanase (800 IU) had no important effects on nutrient digestibility variables. The blends of enzymes had different effects depending on the type of cereal present in the diet but in most cases, nutrient digestibility was improved. Factors associated with the characteristics of the product, type of enzymes used in the combinations, dose and feed ingredients can be cause of the variations found.
Alternative ingredients and coproducts of high-fiber content are increasingly produced and have a great potential to be used in diets for pigs. However, factors that limit their use need to be considered and strategies that improve the nutritional value of these ingredients should be appropriately used in order to obtain beneficial effects on animal health and performance.
Processing methods and use of exogenous enzymes are current strategies applied to improve nutritional value of high-fiber feed ingredients for growing pigs. Extrusion, fermentation and pelleting appear to be effective in most situations. In comparison to the processing methods, the application of exogenous enzymes has more consistent results in the literature, phytase and xylanase being the most widely used enzymes with important benefits on nutrient digestibility, mainly promoting higher calcium and phosphorus digestibility. The use of more than one enzyme in the form of blends or multi-enzyme complex is effective in improving nutrient digestibility, but factors such as the type of enzymes, dose and the variation between different high-fiber ingredients need to be better investigated.
A list of papers published within the last 10 years assessing feed processing methods of high fiber ingredients for pigs, as well as, research investigating the impact of exogenous enzymes to enhance nutritional value of high-fiber ingredients in pig diets is shown in Table 2.
Sources: Jorge Y. Perez-Palencia, Tofuko A. Woyengo and Crystal L. Levesque, South Dakota State University, who are solely responsible for the information provided, and wholly own the information. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.
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