The USA's rapidly growing fuel ethanol industry produces large quantities of corn co-product feed ingredients like distillers dried grains with solubles (DDGS). Use of DDGS in swine feeds is expanding most rapidly, but its use is growing in poultry feeds, too, particularly for turkeys and layers in the Midwest. But ethanol production technology continues to advance and the industry now consists of a few large producers and a multitude of smaller operations, many vying through their various co-products for niches in the feed industry.
As a result, the ethanol boom is boosting diversity and specialization of corn co-product ingredients. Practicing nutritionists formulating monogastric diets have to pay particular attention to the new high-protein products, which have lower energy and phosphorus values. While typical ethanol-DDGS remains attractive for pigs and poultry, a closer look at high-protein DDGS, glutenol, and CPC in least-cost formulated swine diets suggests these ingredients may be more useful in ruminant diets.
Excellent results with 10% DDGS
Currently, North American pork producers are achieving excellent results with high-quality, gold-colored corn DDGS at inclusion rates of 10% in a range of diets. Based on studies at the University of Minnesota, the maximum recommended dietary inclusion rates of golden DDGS are: Gestation50%; lactation20%; post-weaning (with pigs weighing more than 7 kg or 15.4 lbs)25%; and, grow-finish20%. However, by formulating diets on a digestible amino acid basis and using other protein sources high in threonine, formulators can maintain growth rates on grow-finish diets with high-quality DDGS up to 30% inclusion. Moreover, adding golden DDGS plus phytase to swine diets can reduce phosphorus excretion dramatically. See ‘Corn by-product diversity and feed value to non-ruminants' (www.ddgs.umn.edu/mnc2005/Shurson-2005%20MNC8-11.pdf).
Now, however, new technology to enhance yields in dry-grind ethanol plants is changing the mix of co-products. New enzyme applications are increasing the crude protein (CP) content of DDGS, removing the germ or bran from corn prior to fermentation, and removing phosphorus prior to producing DDGS. These changes in ethanol processing also may have the effect of reducing the resulting co-products' nutritional and economic value in monogastric diets.
Cost of higher protein
As CP in DDGS increases, other nutrients must decrease in concentration. For example, one company's branded high-protein DDGS product has 34% more CP than the company's standard branded DDGS (see table Comparing DDGS products'). Much of this increase in CP content is at the expense of fat (59% reduction) and phosphorus (42% reduction). In fact, the relative proportion of nutrients in the high-protein DDGS is similar to that found in distillers dried grains (DDG). Although high-protein DDGS has less neutral detergent fiber (NDF), the reduction in fat content is likely to substantially reduce the energy value for swine and poultry.
Moreover, roughly 50% of the diet cost savings of using DDGS in swine diets results from lower levels of inorganic phosphorus supplementation. So, the much lower phosphorus content of high-protein DDGS may make it more difficult to achieve the same degree of diet cost savings as provided by ‘typical' DDGS.
Glutenol and CPC are two other corn co-products from modifications of dry-grind ethanol processing. They both have substantially higher CP content than typical DDGS, although lysine and other amino acids are not increased proportionately (see table Glutenol and CPC'). The high crude protein:lysine ratio may even reduce energy utilization in monogastrics because of the additional energy needed by the animal to remove excess nitrogen.
Least-cost formulating with DDGS
What is the relative nutritional and economic value of typical corn DDGS compared to other new distillers co-products?
To answer this question, a small group from the University of Minnesota and Agri-Nutrition Services, based in Minnesota, formulated typical swine grower diets on an ‘as fed' basis using assumptions detailed in ‘Corn by-product diversity' referenced above. For cost comparison, we used typical 2005 feed ingredient prices (see table Ingredient prices').
As a reference point for our hypothetical diets, we formulated a standard corn-soybean meal grower diet (called Diet 1) containing 3 lbs of synthetic lysine on a per-ton complete feed basis. Diet 2 was formulated to contain 10% typical DDGS (shown as Spec 1 in table Comparing') and 4.13 lbs of L-lysine HCl. Diet 3 was formulated with 10% Spec 1 DDGS to contain L-lysine HCL (5.78 lbs) plus L-threonine (0.65 lbs), because threonine is second limiting in corn-soybean meal-DDGS diets. We then formulated an additional dietDiet 4containing 10% high-quality, golden DDGS (shown as Spec 2). In this way, we were able to compare Diets 3 and 4 and thereby demonstrate the importance of knowing the source of DDGS, having accurate DDGS nutrient specifications, and understanding how nutrient specifications can affect the opportunity cost for DDGS.
Adding 10% of Spec 1 DDGS and a non-fixed amount of L-lysine HCl to a swine grower diet on a per-ton basis replaced 146 lbs of corn, 55 lbs of soybean meal, and 6 lbs of dicalcium phosphate. This inclusion rate of typical DDGS also increased the amount of choice white grease by 2 lbs, limestone by 3 lbs, and L-lysine HCl by about 1 lb in order to provide dietary ME, digestible lysine, calcium, and available phosphorus levels equivalent to the standard corn-soybean meal diet containing 3 lbs of L-lysine HCl (Diet 1).
Given the 2005 ingredient prices, therefore, adding 10% typical DDGS to a swine grower diet reduced diet cost by $2.34/ton. When 10% of this DDGS and a non-fixed amount of L-lysine HCl and L-threonine were added (Diet 3), diet cost reduced by an additional $1.55/ton.
Cautionary note: In practice, adding high levels of synthetic amino acids by this formulation approach may be risky until we have data showing that it can achieve satisfactory growth performance.
Nonetheless, using Spec 2 DDGS as in Diet 4 at the same price as Spec 1 DDGS, actually increases the diet cost $0.20/ton compared to Diet 3, which uses Spec 1 DDGS. Thus, in our analysis, Spec 2 DDGS is worth $78/ton and Spec 1 DDGS is worth $80/ton because of differences in lysine, sulfur amino acids, and threonine levels. Clearly, DDGS nutrient specifications can affect the ingredient's opportunity cost.
DDGS versus high-protein co-products
Using the same approach, we also compared the addition of 10% high-protein DDGS (shown as HP-DDGS in table Comparing') to Spec 2 DDGS in a swine grower diet. The HP-DDGS slightly reduced the amount of corn (- 20 lbs), soybean meal (- 5 lbs), L-threonine (- 0.4 lbs), and DL-methionine (- 0.14 lbs) per ton of complete feed. However, HP-DDGS also increased the amount of choice white grease (+ 24 lbs) and dicalcium phosphate (+ 3 lbs). Increased fat addition resulted from our lower estimation of the actual ME value of high-protein DDGS, stemming from its lower fat content compared to typical DDGS.
These formulation scenarios clearly show the importance of knowing the actual energy value of distillers co-products; it has a substantial impact on their feeding and economic value in swine diets. Processes that reduce the fat content of DDGS and other co-products significantly reduce the energy value which makes them less viable in least-cost formulations. Also, the lower phosphorus content of the high-protein DDGS adversely affects its economic value. Phosphorus is the third most expensive nutrient added to corn-soy swine diets and more dicalcium phosphate or other phosphorus from another source would be added to meet requirements.
Based on our analysis, using the price for DDGS at $80/ton and the nutrient content assumptions for high-protein DDGS, one could afford to pay only $51/ton for HP-DDGS for swine diets.
Both CPC and glutenol are even higher in CP content than high-protein DDGS. Given our estimated energy value for these co-products and their poor protein quality (low lysine content), least-cost formulation for swine diets results in only minimal reductions in corn and soybean meal use compared to adding the same level of typical DDGS. In fact, an additional 0.7-0.8 lbs of L-lysine HCl per ton of complete feed needs to be added to the diets containing these products in order to achieve the desired level of digestible lysine. The slightly higher phosphorus content of CPC compared to DDGS is an economic advantage. But this advantage does not exist for glutenol. Using the 2005 ingredient prices, our estimates show CPC in swine diets valued at $61.60/ton and glutenol at $63.40/ton. These economic values are substantially less than for typical DDGS.
For all distillers corn co-products, metabolizable energy content, amino acid levels and digestibilities, and available phosphorus content are the primary factors that influence their suitability for use in swine and poultry diets. These factors directly influence the economic value of DDGS and related co-products in their increasingly diverse forms. Based on our assumptions for energy value, the high-protein DDGS, CPC, and glutenol co-products have much higher value for ruminants because of the higher levels of nitrogen as CP and lower levels of fat and phosphorus.