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DDGS as feed ingredient
On the european market are available DDGS sorting from the industrial transformation basically of corn or wheat: geographically, their origin is related to the countries that have started in a more extensive way the industrial production of ethanol for fuel use (i.e.: Austria, Germany, and some eastern Countries, intra or extra UE).
DDGS are nothing more than the concentration of what remains of a cereal once that its starch part has been removed, to be fermented for producing ethanol:
This means that in the DDGS there is a concentration of about three times higher for all the nutrients that were in the cereal of origin and that were not starch.1.
From the cereal, starch (equal roughly to 65-70%) is extracted
2.
From the extracted starch, ethanol is produced by fermentation (about 50% of the starch becomes ethanol, the rest being lost as gas). Therefore from 1 kg of cereal, about 300-350 gr. of ethanol are obtained.
3.
The 30-35% of meal remaining after the extraction of the starch are the basis of the DDGS
Proteins are about 9% in corn, and 11% in wheat: protein content of corn-DDGS is about 28/30%, while in wheat-DDGS is around 33/35%.
Fat is about 4% in corn, and 2/2,5% in wheat, oil content of corn-DDGS is over 10%, being lower for the wheat one.
The same is for fiber. So, everything OK?
Not exactly, for three reasons:
· The first being that in the DDGS do concentrate also substances that are not exciting for nutritional use, mainly mycotoxins and non starch polysaccharides (NSP)
· The second lying in the fact that the nutritional value of the crude proteins of DDGS is highly variable, depending on the thermal stress to which the feedstuff is submitted along the industrial processes, that are not standardized , and
· The third being the high concentration of vegetable oils in the DDGS, with obvious implications in the carcass quality concern.
How to face to the three major problems of DDGS
The mycotoxin risk in DDGS is high, also keeping in mind that if a batch of cereal somewhere is found to be of relatively poor quality for feed or food use, it is most probable that will be sent to the fuel chain, before to be wasted… so controls on this side would have to be reinforced at the feedmill level, and in the most critical of the cases the inclusion in the feed of a good quality mycotoxin binder can become obligatory…obviously the cost of the binder being paid from a reduction of the cost of the DDGS of non perfect quality standard!
As per general, when a supplier of DDGS is found to be critical on the mycotoxin side on a repetitive basis, it has to be abandoned: the first requirements of our animals (and also our interest) is that we do not poison them via the feed!
The NSP concentration is critical mainly when wheat-DDGS are used, but cannot be excluded when corn in cereal of origin: the xylane/ßglucan content will be found multiplied by three in the DDGS, with serious impairment of the viscosity parameters in the gut. When large doses of wheat-DDGS are used without corrections, the feces of the pigs are so sticky that also the less accurate of the farmers will note it in few days. The correction is simple, consisting in the inclusion in the feed of a valuable xylanase/ßglucanase/cellulase enzyme complex, that will boost the nutritional value of DDGS, counteracting their effect of the intestinal viscosity. As more as the supplier will be able to show that the commercial product is “fitted” to DDGS, as better it will be.
On the enzyme side, it has to be recorded that DDGS usually have a very good phosphorus content (0,8-1,0%), that strengthens the justification for the inclusion in the feed of a phytase, as it is a standard now in EC. The sulfur and NaCl content of DDGS, a little higher than the normal, have to be kept in account only when very large doses (over 25% of the feed) are used.
Regarding the heat stress on protein, a general and simple principle is to look at the color of the DDGS: as darker they are, as less digestible will be their proteins and aminoacids. The more their color is close to the one of the cereal of origin, as more they will perform well under the protein point of view. Keep this in mind, before to start with expensive digestibility trials.
Finally, the relationship between the unsaturation degree of the deposit fats in the carcass and the level of the same in the feed is clearly established: therefore, there is no other chance, if the PUFA level in the fat carcass is a target, than to keep out the DDGS from the feeds in the finishing phase.
To get a good quality deposit fat, no more than 1,75% of C18:2 (linoleic acid, the marker) has to be present in the feed; this means a very strong limitation in the percentage of DDGS that can be used, as they have a C18:2 content of 5-6% minimum.
An enormous quantity of research is available for DDGS in the bibliography, as in some countries enormous quantities of this byproduct need to be exploited in the feed chain: a reasonable and prudent use will keep in account the specific quality parameters of the available source, the quality parameters of the animal product that is aimed to build, and the current cost/ton of the DDGS dynamically compared with the traditional and well known feedstuffs.
