Swine nutritionists are scrambling to keep up with nutrient profiles.

One of the hot topics concerning dried distiller's grains with solubles (DDGS) these days involves carcass fat quality, says a University of Minnesota animal scientist.

DDGS is a good energy source for pigs, but it has its limitations, Jerry Shurson told participants of the recent Minnesota Nutrition Conference. Shurson is an expert on DDGS, having studied the by-product of ethanol production for eight years.

DDGS is the dried residue remaining after the starch fraction of corn is fermented with selected yeasts and enzymes to produce ethanol and carbon dioxide. After complete fermentation, the alcohol is removed by distillation and the remaining fermentation residues are dried.

“Nutritionists and producers want to feed more than the typical 10% level of DDGS for greater cost savings, but little research has been done to evaluate the effects on growth performance and carcass quality in grow-finish pigs,” notes Shurson.

There are three DDGS issues the swine nutritionist and his Minnesota colleagues are currently investigating:

  • Impact on pork fat/quality, especially in pork bound for Japan;

  • How to deal with variability of by-products between plants; and

  • The circumstances under which intake drops as DDGS levels increase.

Several studies of these issues regarding DDGS have just been completed and two more studies are underway.

Ten Percent Level on Pork Fat

One field study, funded by Land O'Lakes/Purina Feed, evaluated the impact of feeding conventional corn-soybean meal diets, with or without 10% DDGS, on pork fat quality.

The study was conducted in two, typical 1,000-head commercial finishing barns in southern Minnesota. Both were stocked with Monsanto genetics.

Feed was formulated and provided by Land O'Lakes/Purina Feed. One producer fed typical diets; the second fed 10% DDGS. A seven-phase, mixed feeding program was fed and the last finisher diet contained 4.5 g./ton of Paylean (Elanco Animal Health).

Diets within each phase contained similar nutrient levels. All rations contained the same level of choice white grease as a fat source, ranging from 1.25 to 3.75%, depending on the diet phase.

Pigs were slaughtered at Hormel Foods in Austin, MN, and a sample from each group was evaluated for carcass traits. Mid-belly samples were taken and a visual color score was determined by a group of panelists using the National Pork Board's Japanese pork fat color standards.

Complete fatty acid profiles were also conducted on belly samples. Iodine value and mean melting point were calculated using fatty acid data from each sample.

As shown in Table 1, pigs fed the 10% DDGS grew as well, consumed less feed and had better feed conversion and lower feed cost/lb. of gain than pigs fed the corn-soy diet without DDGS.

At slaughter, there were no differences in carcass weight, backfat or percentage of ham, loin and belly relative to total carcass weight (Table 2). In addition, there were no differences in loin depth or percentage of lean muscle in the carcasses between the two groups.

These results are in agreement with performance and carcass composition results in initial studies at Minnesota, Shurson says, and show 10% levels of DDGS have no negative effects on growth or carcass of grow-finish pigs.

When belly fat was evaluated, there was no difference in color score based on the Japanese pork fat quality standards, nor were there any differences in the melting point of the fat (Table 3).

However, bellies from pigs fed the 10% DDGS had a higher iodine value than pigs fed diets without DDGS. Iodine was still below a suggested maximum threshold of 70.

“Iodine value is a ratio of unsaturated fatty acids to saturated fatty acids. Since it is a ratio, it has no units. Think of it like feed/gain,” explains Shurson.

Carcass Iodine Values

Iodine value is used as criteria for measuring pork fat quality. A maximum iodine value of 70, established by the Danish Meat Research Institute is considered standard in Europe. In addition, European dietary specifications generally include a maximum dietary level of 1.6% linoleic acid for finisher pigs.

Similar thresholds have not been established for pork produced in the United States, explains Shurson. It has been suggested that an iodine value limit for pork fat be set at 74, and dietary linoleic acid levels be set at a maximum of 2.1% of the diet, because pigs fed a corn-soybean meal diet with no added fat could exceed an iodine value of 70, he says.

“Some packers don't want to go over an iodine value of 72, some 70,” Shurson continues. “The question becomes, if iodine value indicates pork fat quality, what number should we use? If 72 is the target, our data shows we can feed 30% DDGS.”

Soft fat is the number one factor for downgrading and reducing price for pork bound for Japan, Shurson says. He adds there is no evidence that feeding 10% DDGS will hurt the quality and acceptability of U.S. pork destined for the Japanese market.

Other Feed Value Concerns

Shurson and his colleagues recently completed a sow lactation study, where diets contained up to 30% DDGS. They found the dietary DDGS level had no significant effect on average daily feed intake.

In studies where feed intake has been affected, Shurson says it is unclear whether mycotoxins were involved or other quality problems existed, such as overheating of the DDGS, which could contribute to reduced feed intake.

They have identified other limitations to feeding DDGS:

  • A slight reduction in dry matter digestibility, which means slightly more manure.

  • An increase in nitrogen excretion. However, phosphorus excretion may be reduced.

  • Low particle size from some ethanol plants, which can cause problems with flowability.

  • Ability to pellet DDGS is a concern, particularly to integrators in the southeast, who use pelleted sow feed.

  • Quality variability and a perceived risk of mycotoxins.

New Processes Yield Less-Valuable Product

“From ethanol conferences I've attended, it appears plants are moving toward fractionalization,” says Shurson. He explains that due to high natural gas prices and the challenges of getting rid of the syrup or solubles that are produced, Minnesota ethanol plants have modified their processes to burn the solubles as a fuel source for the plant, and subsequently, are producing dried distiller's grains (DDG), a less valuable product.

Other upper Midwestern ethanol plants are using various fractionation processes to remove the germ, bran and perhaps other components of the corn kernel before going into the fermenter to increase efficiency of ethanol production. Along with fractionalization, changes in enzymes and heat used in the process are also altering the nutrient composition and digestibility of distiller's by-products.

“These are new ingredients we've never seen before. Some will be good for the pig and some not,” Shurson points out. “The challenge will be identifying high-quality, consistent sources of DDGS and evaluating the feeding value of new fractionated by-products as they enter the market. We'll have to hustle to keep up.”

The Minnesota swine nutritionist offers several strategies to help deal with variability in nutrient content and quality among DDGS sources:

  • Identify sources that have implemented a comprehensive DDGS quality assurance program, preferably ISO 9000 and HAACP certified;

  • Limit the number of sources used;

  • Question generic nutrient specification values provided by the supplier when formulating diets;

  • Request current, complete nutrient profiles from sources being considered. The University of Minnesota has nutrient profile information for several DDGS sources on its DDGS Web site: www.ddgs.umn.edu.

  • Request evidence of consistent quality and nutrient content from each source.

Studies will continue looking at feeding higher levels of DDGS and the effect on carcass traits and intake. Shurson has partnered with Hormel Foods to study the effect of DDGS on fat quality. Results should be available by the end of the year. They also hope to establish net energy values.

“The ethanol industry is here to stay,” says Shurson. “We are going to have piles of the stuff for all species of livestock. We need to figure out how to make it work without compromising performance, cost or quality.”

Table 1. Performance, Feed Usage and Feed Cost of Grow-Finish Pigs Fed Diets Containing 0% or 10% Dried Distiller's Grains with Solubles (DDGS)
Item 0% DDGS 10% DDGS
Average daily gain, lb. 1.81 1.84
Average daily feed intake, lb. 4.94 4.62
Feed/Gain 2.73 2.54
Pounds feed/head 570 554
Feed cost/lb. gain, $ 0.17 0.16
Table 2. Carcass Characteristics of Grow-Finish Pigs Fed Diets Containing 0% or 10% Dried Distiller's Grains with Solubles (DDGS)
Item 0% DDGS 10% DDGS
Carcass weight, lb. 212 210
Last rib backfat, in. 1.09 1.11
Tenth rib backfat, in. 1.01 0.99
Ham, % 11.74 11.74
Loin, % 7.93 7.91
Belly, % 10.51 10.41
Loin depth, in. 2.72 2.72
Carcass lean, % 56.36 56.47
Table 3. Mid-Belly Fat Quality Characteristics of Carcasses from Grow-Finish Pigs Fed Diets Containing 0 or 10% Distiller's Dried Grains with Solubles (DDGS)
Measurement 0% DDGS 10% DDGS
Japanese fat color score 1.76 1.81
Mean melting point, °C. 29.3 (84.7°F) 28.7 (83.7°F)
Iodine value 66.7 68.3
Oleic acid (18:1), % 47.39 45.12
Linoleic acid (18:2), % 11.94 13.98
Saturated fatty acids, % 33.99 34.26
Monounsaturated fatty acids 51.78 49.47
Polyunsaturated fatty acids 14.02 16.11
Total omega-3 fatty acids 0.98 0.96
Total omega-6 fatty acids 13.02 15.14
Omega 6:omega 3 ratio 13.28 15.78

DDGS Quality Assurance an Issue

Bankers and investors in ethanol plants realize that 10 to 15% of their revenue stream is from sales of distiller's by-products, says Jerry Shurson, University of Minnesota swine nutritionist.

He believes plants are looking for by-products marketers who are more customer sensitive and willing to develop production systems that ensure more consistent, high-quality by-products.

At least one major ethanol plant is implementing a DDGS Quality Assurance Program to improve consistency, quality and transparency of their by-products, according to Shurson. However, many are still unconcerned or unaware of the importance of product quality.

There are no distiller's by-product quality standards in the ethanol industry. Instead, many are moving toward branding their by-products to differentiate ingredients, he says.

As ethanol plants pop up around the country, producers know they must compete with the industry for corn. Based on ethanol prices and production costs (September 2006), many modern ethanol plants can afford to pay as much as $7 to $8/bu. of corn to break even, adds Shurson.

“It's understandable why pork producers are getting nervous about their current and future feed costs,” he notes. “Our challenge is to identify high-quality, consistent sources and evaluate the feeding value of their by-products.”