Adding distillers’ grains with solubles to swine diets has gained momentum as a potential ingredient to reduce feed costs. Certainly with the increase in ethanol manufacturing, DDGS is much more readily available today.

Although the starch portion of corn is removed during fermentation, the resulting DDGS composition is a direct reflection of the corn. In general, the DDGS nutrient content contains three times the amount of protein, fat, fiber and minerals than the original corn. While the actual nutrient composition of corn and DDGS are vastly different, the energy value is recognized as being similar.

A major difference between corn and DDGS when formulating diets is that, while DDGS is higher in protein, the amino acid digestibility is lower. In fact, the actual lysine amount and its digestibility can decline in DDGS when heat damage has occurred from the drying process. Thereby, if the lysine-to-crude-protein ratio is 2.8 percent or greater, then the DDGS has an average or above average quality. If the ratio is lower than 2.8 percent, then the product has a reduced quality and is not recommended for swine diets.   

Along with selecting a high-quality source, higher levels of synthetic lysine are key to moderating the overall dietary crude protein. Since DDGS is a relatively poor lysine source compared with its overall crude protein level, it brings with it an abundance of other amino acids. Instead of dietary methionine or threonine limiting the synthetic lysine levels, tryptophan levels become the determining factor in diets containing greater than 10 percent DDGS.

DDGS levels in grow/finish diets typically range from 10 percent to 15 percent. This is consistent with most published data indicating that growth performance can be maintained when a high-quality DDGS source is used and diets are formulated on a digestible-amino-acid basis with high synthetic lysine levels. However, some producers with access to a consistent supply of high quality DDGS use levels as high as 30 percent. These producers also often have detailed performance records and/or commercial research facilities to document performance changes.

One consequence of feeding DDGS in grow/finish diets is a documented decline in carcass yield. On average, the expected decline is 0.4 percent to 0.5 percent for every 10 percent DDGS in the diet. The thought is that the decline is due to the extra fiber and protein in diets with DDGS; both can increase visceral weight. Take that effect into account when determining DDGS’ value, since a lighter carcass will mean a loss in revenue.

Dietary Economics

Corn and soybean meal prices are the main influences on the economics of using DDGS in grow/finish diets, as DDGS replaces both products. Also influencing the economics, but to a lesser degree, are the prices of synthetic lysine, supplemental phosphorus (monocalcium or dicalcium phosphate) and limestone. 

The synthetic lysine level that can be used increases as the DDGS level increases in the diet. The greatest economic advantage occurs when adding the first 10 percent DDGS to a corn/soybean-meal-based diet. The reason is that the greatest incremental increase in synthetic lysine use occurs when DDGS goes from 0 percent (~3 pounds per ton) to 10 percent (~5 pounds per ton), with only small additional increases at 20 percent (~6 pounds per ton) and 30 percent (~7 pounds per ton) DDGS due to other amino acids becoming limiting. These synthetic lysine levels directly affect the relative amount of soybean meal that you can replace in the diets. Thereby, the value of increasing the dietary DDGS level is not linear. Rather, the greatest economic benefit is for the first 10 percent, with smaller incremental increases to higher levels.

Along with DDGS having a higher phosphorus concentration compared to corn (again, by about three times) the availability is higher, as well. This reduces the need to supplement phosphorus. In fact, supplemental phosphorus decreases by ~50 percent with 10 percent DDGS added to a corn/soybean meal diet.  At 20 percent DDGS, only a small amount of supplemental phosphorus is needed for the grower stage and none for the mid- to late-finishing stages. So, the greatest savings relative to phosphorus supplementation occur up to about 20 percent, with little additional cost savings at higher levels. During the past few years, the supplemental phosphorus price has steadily increased, which increases DDGS’ economic advantage.

While limestone pricing has only a slight impact on DDGS economics, the dietary level increases with increasing DDGS amounts. Therefore, as the price of limestone increases, a negative effect on DDGS economics occurs, although it’s very minimal.

Software Tool

To quickly determine the economics of using DDGS in corn/soybean meal grow/finish diets, the Kansas State University Swine Nutrition Team has developed a spreadsheet. This calculator allows for economic calculations based on corn, soybean meal, monocalcium phosphate (21 percent P), L-lysine HCl, limestone and DDGS prices. 

Once ingredient prices are entered, changes in diet cost and approximate savings per pig are calculated at dietary DDGS levels of 10 percent, 20 percent and 30 percent. These values are based on diets formulated on a digestible-amino-acid (Standard Ileal Digestible) and available phosphorus basis, using a high-quality DDGS source. While diet formulations will vary when using DDGS, the diets used for this calculator provide an approximation for comparison. Also, the economic values assume that growth performance is not altered at the various DDGS levels. 

Along with diet and per-pig savings, it calculates a breakeven price for DDGS. Because ingredient changes are not in equal proportion for each 10 percent DDGS that’s added, the breakeven price for DDGS will almost always be higher for the first 10 percent addition compared to higher DDGS levels.

Yield Influences

With DDGS’ clear impact on carcass yield, the spreadsheet also provides a second calculation. It accounts for carcass weight, carcass price and the amount of yield decline you can expect for every 10 percent DDGS fed. You can select options ranging from a 0 percent to 0.6 percent decline in carcass yield. 

Since carcass weight will decline due to the yield reduction, it calculates a yield cost per pig. The approximate savings per pig is then determined by subtracting the yield cost per pig from the approximate savings from the feed cost alone. So, it calculates a new breakeven price considering the yield reduction. Figuring that into your DDGS economics, a lower breakeven price is established due to lost revenue from a lighter carcass sold.

While there are many options to consider when adding DDGS to your grow/finish diets, there also are more answers surfacing every day. The Kansas State Calculator helps you dig deeper and uncover more of the information you need to make sound decisions.