Distillers dried grains with solubles (DDGS) formulations were thought to be an inferior option for swine diets, but in recent years new processing techniques and improved quality control measures have created more consistent nutrient profiles to formulate cost-effective diets.
DDGS levels, health concerns
In some markets, DDGS inclusion rates are reaching 40% in gestation diets, 20% in lactation diets and 30 % or more in growing-finishing diets.
“Diets containing DDGS should be formulated on the basis of digestible amino acids and digestible phosphorus,” says Hans Stein, extension swine nutritionist, University of Illinois. “In general, 10% DDGS can replace approximately 4.25% soybean meal and 5.7 % corn if 0.1% crystalline lysine is included in the diet.”
According to Stein, DDGS can be included in nursery pig, growing-finishing pig and sow diets at the rate of 20% and at the rate of 40% for gestating sows.
“At these inclusion rates, excellent performance of pigs has been reported provided that diets were formulated on the basis of digestible amino acids,” Stein says. “Greater inclusion rates are possible, but may not always maximize pig performance.” Driven by ingredient costs, inclusion rates of 30% or greater in growing-finishing diets have become more commonplace.
But are pigs still performing optimally when DDGS are included at the higher end of the spectrum?
“We have field reports of producers experiencing a growth loss of 10 to 15 pounds during the growing-finishing period, or that the growth period when they increase DDGS levels is extended by about a week when high levels of DDGS are used,” says Dr Brad Lawrence, technical services manager for Novus International.
“There have also been reports of late-term abortions following administration of certain vaccines when high levels of DDGS are fed in gestation, as well as incidences of foot pad lesions during finishing. The most frequent reports are of an increased incidence of Mulberry Heart Disease symptoms in offspring from sows fed high DDGS diets.”
Why the challenge?
When pigs consume secondary oxidation products, feed intake can drop off, leading to additional concerns because nutrient needs are no longer being met. In three studies evaluating the feed intake and palatability impact of DDGS inclusion in diets of growing pigs, researchers from Kansas State University concluded that, regardless of source, feed intake is decreased when DDGS is included in the diets. Although it seems that the metabolizable energy content of DDGS is comparable to that of corn, feed consumption may affect pig performance, even when DDGS is included at low concentrations in diet formulations.
Feed intake reduction causes a decline in consumption of proper nutrients vital in helping growing pigs manage oxidative stress. Oxidative stress arises when production of harmful free radical compounds exceeds the body’s natural ability to detoxify them.
Changes in cellular fatty acid profiles
A pig is what it eats, or at least it is as far as fatty acid profiles are concerned. In fact, one of the most common challenges voiced by producers with respect to DDGS use is the increased attention to iodine value, an indicator of the unsaturated fat content, in the carcass.
Unsaturated fats are more prone to oxidation. The cell membranes from pigs fed 3% corn oil from a diet containing 30% DDGS are more prone to oxidative damage than cell membranes from pigs fed a typical corn-soy diet getting traditional choice white grease. When these cell membranes are damaged, there is an unseen cost in both energy and amino acids to repair or replace these cells. This repair process harms growth, decreases feed efficiency and raises production costs.
Managing vitamin E status
Vitamin E is critical for maintaining oxidative balance. Recent work with sows fed an unstabilized animal/vegetable fat blend showed that supplementation with an antioxidant, when fed at 0.5 pounds per ton, improved serum vitamin E status 25%.
It is believed that vitamin E, in conjunction with selenium, works to form the free radical first line of defense. Vitamin E status of the pig is also affected by supply of selenium for normal vitamin E “recycling.” A deficiency of vitamin E and selenium is often seen with Mulberry Heart Disease symptoms in suckling and weaned pigs, a condition that has been associated with feeding high levels of DDGS in some cases. Inclusion of DDGS at higher levels requires careful management of vitamin E status.
Organic selenium is used in the North American pork industry to improve the selenium status of offspring. It was thought that increased levels in milk resulted in subsequent increased selenium intake in the suckling pig and a building of selenium stores in tissues for the post-weaning period. Analysis of milk samples shows some evidence of reduced levels of selenium secreted in milk when feeding higher levels of DDGS.
Reducing risk of sulfur antagonists
Compared to the concentrations of sulfur in corn, that in DDGS, like many other nutrients, is magnified at least three-fold due to manufacturing. DDGS high in sulfur can result in decreased uptake and absorption of copper and selenium. Feeding a high-quality organic mineral supplement containing copper can provide a highly stable and available form of organic copper that stays intact through the low pH environment of the gut.
Selenium in organic forms is vital to keeping a pig’s system in oxidative balance. Selenium is a key mineral co-factor for glutathione peroxidase, which converts hydrogen peroxide to safe compounds for the body. Research with lactating sows has shown that supplementation with a selenium-enriched yeast at 0.3 ppm increases milk selenium by about 0.04 g/ml.
Mycotoxins risk magnified?
There is evidence that mycotoxins can be concentrated three times in DDGS compared to the grain itself. Recent studies have shown that consumption of aflatoxins could have a dramatic impact on liver oxidation markers as well as serum vitamin E status.
A dramatic increase in daily mycotoxin intake may occur when mycotoxins are concentrated in DDGS and then the distillers grains are included in the diet at 30-60%, presenting a significant oxidative challenge to the pig.
Many mycotoxins are biotransformed in the liver. Free radicals are produced when mycotoxins are consumed, that negatively affect oxidative balance. The work by Harper et al., (2009) found that use of a clay-based flow agent alone or use of a synthetic antioxidant blend could improve serum vitamin E status in the face of aflatoxin challenge.
This research confirms that even when a product is used that restores feed intake in the face of mycotoxins, enough mycotoxin can still be absorbed to potentially harm oxidative balance and potentially result in negative health consequences to the animal. The best mycotoxin management plan includes a product that minimizes mycotoxin absorption in conjunction with a synthetic antioxidant blend than can improve vitamin E status.
Continue careful monitoring
Production economics are driving increased DDGS use in all phases of pork production, pushing inclusion levels to their limits. The economic benefits of using DDGS when formulating pig diets should not be ignored. But the price to be paid for that lower input cost comes with the need for more careful management and necessary supplementation of the diet to avoid oxidative stress and reduced performance.
One of the main risks associated with feeding high levels of DDGS may be compromised oxidative balance affected by mycotoxins, potential oxidation products, alterations in the tissue fatty acid profile to more unsaturated fatty acids, and decreased selenium and copper status. Obtaining and maintaining oxidative balance requires a strategic approach to pig nutrition with the right tools to combat specific challenges associated with feeding conditions and diet ingredients.