There is no doubt. Dried distillers grains with solubles, or DDGS for brevity, have been a great money saver for most North American pork producers. Today, many producers use about 20-30% DDGS in finishing diets, whereas the inclusion rate reaches even 60% in some gestation diets. The problem is not if DDGS should be used, but rather, how much more can be used before problems start to appear. And, DDGS is not without its problems!
First comes nutrient variability due to slight differences in the production methods employed by the myriads of small and not so small ethanol producers. This is a problem easily solved when one buys from a fixed source, but it can be a headache when material is sourced from a variety of DDGS producers.
Here, we must recall that the nutrient composition of DDGS is about three times concentrated that of normal maize, minus of course the starch. Thus, protein, fibre, and lipids are the main nutrients provided by DDGS.
Another potential problem of DDGS as a feedstuff for pigs is its relatively low lysine digestibility. This is because as part of ethanol production and subsequent drying of DDGS, maize is exposed to rather high temperatures that cause Maillard reaction. This renders lysine (and other amino acids to a lesser extent) partially unavailable for the animal. This is not a problem that can be fixed at the feed mill!
One of the most recent problems, arising from the increasing inclusion rate of DDGS in finishing diets is soft carcass fat that makes processing of meat parts a rather tedious task. This appears to have been overcome by some packers as they adapted processes to handle carcasses at a cooler temperature. Soft carcass fat is a consequence of using too much maize because this ingredient is rich in unsaturated fatty acids. And, here we should keep in mind that most North American diets for pigs are based on maize as the main cereal so this problem becomes even more of a concern with a high inclusion level of DDGS.
Finally, it should be reminded that as nutrients concentrate in DDGS, so do mycotoxins. Thus, a mycotoxin monitoring system and a proper anti-mycotoxin agent should be part of a feeding program using high levels of DDGS. This is often forgotten causing quite a bit of trouble!
The most recent issue regarding DDGS in North America is how to increase their use or how to make more out of their use by including enzymes in pig diets. Here, there are two potential types of enzymes that could be of benefit; Carbohydrases and proteases. The first class of enzymes can break down the non-starch polysaccharides in maize. Research and practice however remain unclear, perhaps because the pig never had any problems digesting and using these 'soft' fibres compared to the more 'resistant' fibres in cereals like wheat and barley.
Proteases on the other hand appear more promising, especially since DDGS contain more protein than fibre, but here again pigs never had much trouble digesting maize protein, so results remain largely inconclusive. Certainly proteases cannot improve digestibility of amino acids destroyed during thermal processing, as discussed above. Still, there is more research going on, so this is something to be monitored.
So, what is to be done? First, a careful understanding between the packer and producer to identify at which level carcass quality starts to affect negatively profitability for both parts. Then, a source of DDGS of standard (and hopefully of high) quality to ensure pig performance should be secured. Finally, a nutrition program tailored to match animal needs to available ingredients should try to minimise nutrient wastage to ensure reduced feed cost and maximal profitability. Dried distillers grains with solubles remain a valuable ingredient, prized not only in North America but also in other countries where it is produced or imported. Understanding its shortcomings is the best way to enhance its beneficial use.