Swine & U

Much has changed over the last 20 years in the choices of feed ingredients available and the way swine diets are formulated. One of the most significant changes is the use of corn-derived dried distillers’ grains with solubles (DDGS) in diets for all phases of pork production.

In 1998, when the U.S. ethanol industry was in its infancy, about 1.3 million metric tons of DDGS were produced, and only about 52, 000 metric tons (4 percent) were fed to swine. Today, more than 37 million metric tons of DDGS are produced, of which more than 5 million metric tons (14 percent) are being fed to swine domestically and another 13 million metric tons (35 percent) are being exported for use — primarily in swine and poultry diets in Asia and Latin America.

This dramatic increase in DDGS use in swine diets has occurred for three reasons: Existence of an abundant supply of DDGS in major U.S. pork production states; DDGS have high nutritional and economic value relative to corn and soybean meal; and extensive research demonstrating that DDGS can be successfully used at high dietary inclusion rates — up to 30 percent — in all phases of production to achieve optimal performance.

Regarding metabolizable energy (ME) and net energy (NE) for swine, corn DDGS and corn contain, on average, similar ME and NE content. As a result, DDGS prices are generally highly correlated with corn prices in the feed ingredient market.

However, the energy content varies considerably among sources. One of the reasons for the high variability in energy content among DDGS sources is that the majority — more than 90 percent — of ethanol plants are extracting some of the corn oil prior to manufacturing DDGS. However, research has shown that the oil (crude fat) content of DDGS is a poor single predictor of ME and NE values for swine.

To manage this variability and provide accurate ME and NE estimates of the DDGS sources being used, University of Minnesota swine nutrition researchers (Urriola et al., 2014; and Wu et al., 2016b) have developed and validated prediction equations based on chemical composition.

Commercial companies also use similar prediction equations to help nutritionists and pork producers compare relative economic value and customized energy and nutrient loading values for feed formulation of various DDGS sources. These approaches minimize the risk of overestimating or underestimating energy, digestible amino acid levels and phosphorus content in DDGS as part of a precision swine feeding program.

Although the protein content of DDGS (27 percent) is more than three times greater than corn (8 percent), it is much less than for dehulled, solvent-

UniversityofMinnesota EXTENSION SWINE&U

extracted soybean meal (47 percent). This is one of the reasons

SWINE & U why the DDGS price is less

By Jerry Shurson influenced by soybean meal prices than by corn prices. More importantly, the lysine content relative to crude protein content in DDGS (2.97 percent) is about half the lysine: crude protein in soybean meal (6.2 percent)

Although the concentrations, balance and digestibility of amino acids in DDGS are inferior to those of soybean meal, DDGS can partially replace soybean meal in swine diets when adequate amounts of crystalline lysine, threonine and tryptophan are supplemented. However, like for energy, the amino acid content and digestibility vary substantially among DDGS sources.

Once again, University of Minnesota researchers (Zeng et al., 2017) have developed prediction equations to accurately estimate the standardized ileal digestibility amino acid content of DDGS sources for swine. This further supports precision swine feeding programs when using DDGS.

Another unique and economically valuable nutrition component of DDGS is its relatively high standardized total tract digestible (STTD) phosphorus content (0.47 percent) compared with corn (0.09 percent), soybean meal (0.34 percent), and other grain and grain byproduct sources. Phosphorus is the third most expensive nutritional component in swine diets after energy and amino acids.

As corn is fermented to produce ethanol and DDGS, the phosphorus content is not only concentrated, but much of it is converted to a more digestible form. As a result, substantial amounts of expensive inorganic phosphate supplements can be partially replaced in swine diets when DDGS is added. This not only reduces diet cost, but also reduces the amount of indigestible phosphorus being excreted in manure.

The STTD phosphorus content also varies among DDGS sources, and while prediction equations have been developed to estimate STTD of phosphorus in DDGS for swine, they are not sufficiently accurate. When formulating swine diets, the National Research Council estimate of 65 percent of STTD of phosphorus in DDGS should be applied to the total phosphorus content of DDGS.

Obtaining accurate estimates of energy and the digestible amino acid and phosphorus content of feed ingredients is one of the most important factors