Feed prices continue to rise since cereals can also be used for fuel production. Using biofuel co-products, particularly DDGS in swine feed may therefore be both an affordable as well as sustainable solution.
Over the last months, several reviews have been published about feeding co-products from biofuel industries to livestock including swine. These compilations included a review by FAO and Animal Frontiers (April 2013). Co-products from the biofuel industry vary widely in nutritional composition. Nonetheless, co-products from the biofuel industry provide additional feedstuffs that may enhance flexibility of swine feed formulation. The feed grain markets imply that for the foreseeable future co-products should be used by the pork industry to a much greater extent as feedstuffs in swine feeds. Risks, opportunities, and challenges for the inclusion of dried distiller’s grain plus solubles (DDGS) and crude glycerol in swine feeds are similar to other alternative feedstuffs, such as co-products from food industries for example millrun and canola meal.
Risk management: Energy
To feed pigs diets with an increased content of co-products presents a risk to maintain growth performance and carcass composition. However, some areas in the world have managed this risk to a great extent by using modern feed quality evaluation systems, at least systems that are more modern than used traditionally in North America. Co-products such as canola meal, millrun and DDGS generally have a higher protein and fibre content and lower starch content than grains. Therefore, less starch and more protein and fibre will be used to supply energy to support protein deposition. Better energy systems than digestible energy (DE) and metabolisable energy (ME) are required, because these two systems overestimate the amount of energy supplied by protein and fibre. The net energy (NE) system is such a system. Although the NE system has not been validated for extreme inclusion levels of co-products in swine diets, a large body of evidence of European and North American data suggest that the NE system is superior to the DE and ME system in dealing with large fluctuations in dietary content of macronutrients, especially protein. Two approaches are used to formulate feeds for energy that are high in co-products: formulate to equal NE and attempt to maintain performance, or float energy and let the pigs determine if voluntary feed intake and thus energy intake can be maintained. Both should reduce feed cost per unit of gain.
Risk management: Other
Apart from energy, dietary amino acids should be formulated using the standardised ileal digestible (SID) amino acid system, and the use of total and apparent digestible amino acids for feed formulation should be avoided entirely. Furthermore, phosphorus should be formulated as (standardised total tract) digestible or available phosphorus and not as total phosphorus. Some co-products such as DDGS have a high content of digestible phosphorus and this potential advantage would be ignored if the total phosphorus system is used to formulate swine feeds. Moreover, co-products present a risk because concentrations of mycotoxins or anti-nutritional factors can potentially be higher than in the original cereal grain. For example, vomitoxin or DON can survive the fermentation and drying process, and can thus be concentrated in DDGS in comparison to the feedstock grain.
Carcass and pork quality
Some co-products from cereal grains such as DDGS and oilseeds such as expeller-pressed canola meal contain 10 to 20% residual oil and larger quantities of fibre than the parent feedstock. Thus, feeding increasing dietary inclusion of DDGS will increase dietary fibre and poly-unsaturated fatty acid (PUFA) content that consequently will decrease dressing percentage and reduce fat hardness, respectively. Dietary fibre increases gut weight meaning that pigs should be marketed 1 to 2 kg heavier to ensure that target carcass weight will be reached. The high residual oil content of some co-products provides unsaturated fatty acids that soften pork fat. Dietary PUFA are directly deposited into carcass fat depots; therefore, co-products from flaxseed that are rich in omega-3 PUFA may also increase value-attributes of pork for the consumer. Negative impacts of feeding DDGS on dressing percentage or fat hardness might be reduced by implementing a withdrawal of DDGS prior to slaughter.
Variation in quality
Without question, co-products have a more variable nutrient profile than their feedstock, due to processing being an extra source of variation. For example, one of the main risks associated with the use of DDGS in swine diets is variability in quality, in particular for the first-limiting amino acid lysine due to drying using heat. The risk of protein damage by over- or extended heating or both is well understood and a wide range in lysine damage has been confirmed for DDGS. Apart from heat damage, oil extraction of oilseeds using a range of processing techniques (solvent-extraction, expeller-press, and cold press) causes a range of residual oil content and thus variability in energy value of the resulting meal or cake. The variation can be predicted using chemical analyses; however, near infrared reflectance spectroscopy calibrations must be developed so that the feed industry can mitigate this variability rapidly and effectively. The variation in quality can then be considered during feed formulation to reach diets with planned nutrient density and a predictable growth performance.
Risk management: Guidance
The risk of including an increasing amount of co-products into swine feeds might be managed better by including multiple co-products each at a lower inclusion level in swine diets than a large quantity of a single co-product. Unfortunately, research efforts have been mostly directed towards studying the impact of individual co-products, rather than studying the maximum inclusion level of a mix of co-products. Still, if one of the following feedstuffs, tallow, canola meal, phytase, and DDGS, and perhaps even extruded oilseeds, are currently missing from a producer’s feed formulations for grower-finisher pigs, their feed costs are likely too high. Then, opportunities to develop a more cost-effective feeding programme exist by using additional co-products.
To use local co-products effectively, information on the content of their constituents NE, SID amino acids, and digestible phosphorus is essential and should fit into used data bases for feed formulation. Throughout history, large data bases containing the nutritional quality of these constituents have been acquired for an array of feedstuffs including co-products, especially in Western Europe. This information has been brought to North America and has been used to formulate feeds. The review completed by the 2012 NRC committee ensures that this information together with feedstuff data from North American feedstuff samples is now readily available. Still, a learning curve will follow. For example, differences in macronutrient profile of co-products exist between continents, and foreign data bases should not be adopted without cross checking ingredient values, for example, using laboratory analyses. Correct NE content and ratios of SID lysine to NE will have to be implemented, whereas SID ratios of other amino acids to lysine were more easily implemented. Thus, even though the NE system can predict performance and carcass quality better than DE and ME systems, it does not mean that the NE system can be implemented without reasoned changes in feedstuff and macronutrient composition of formulated feeds.
Economics, societal acceptance and the environment are key components for the long-term sustainability of swine
production. Dietary inclusion of co-products and less reliance on feed grains are important. Feeding co-products provide challenges and opportunities. First, co-products add variability in macronutrient profile in the feedstuff matrix. Therefore, feed quality evaluation for energy, amino acids, and phosphorus content and their availability or digestibility is crucial, as is the system selected for evaluation. Second, co-products may contain chemical residues and mycotoxins that reduce voluntary feed intake and affect reproductive performance. Finally co-product use may reduce carcass characteristics and pork quality. In conclusion, feeding alternative feedstuffs may reduce feed costs per unit of pork produced, but also provides challenges to achieve cost-effective, predictable growth performance, animal health, environmental footprint, carcass characteristics and pork quality.
* Eduardo Beltranena is also associated with Alberta Agriculture and Rural Development.
DDGS in practice
The book Biofuel Co-products as Livestock Feed discusses and summarises current knowledge on these co-products. One chapter defines their use in pig diets. Bottom line is that various co-products can be used, their application may be related to the type of pigs – them being sows, weaners or finisher pigs. Chapter 10 by Shurson and others mainly discusses the pros and cons of the use of dried distillers grains with solubles (DDGS), a cereal byproduct of the distillation process. Main messages include:
• Maize DDGS is the predominant ethanol industry co-product available for use in swine diets in North America. To achieve acceptable performance, good quality maize DDGS can be added at levels up to 30% of diets in all phases of production, and up to 50% in gestating sow diets.
• Maize DDGS is primarily an energy source but also contributes significant amounts of digestible amino acids and available phosphorus to swine diets.
• Limited quantities and information is available on the nutritional value, optimal dietary inclusion rates and benefits and limitations of feeding other maize co-products from the ethanol industry.
• Glycerin is a co-product of the biodiesel industry, has an energy value greater than maize for swine and can be added at levels of up to 6% for weanling pigs, 9% for lactating sows and 15% for growing-finishing pigs toachieve acceptable performance.
• Opportunities exist to use particle size reduction, hydrothermal processing and enzymes to enhance energy and nutrient digestibility of distillers coproducts,but the application and potential benefits of these technologies are not well understood.
• Special consideration should be given to the methanol content of crude glycerin, and to the possible presence of mycotoxins in DDGS when using themin swine diets.
• Feeding diets containing increasing levels of DDGS to growing-finishing pigs reduces pork fat firmness, but reducing feeding levels, withdrawing it from the diet for a period of time before harvest and adding conjugated linoleic acid to the diet three to four weeks before harvest can minimise the negative effects of DDGS diets on pork fat quality.
Source: Pig Progress 29.4