A Wider Choice of Distillery Feeds


Until recently distillers’ grains came essentially in three forms: draff from a malt distillery; yeast-enhanced grains from a grain distillery; and dried, dark distillers’ grains which incorporated a proportion of the ‘solubles’ that remain after distillation (DDGS). All of them included higher concentrations of protein, oil, fibre and ash than the original grain, and over many years they all made significant contributions to the diets of beef and dairy cattle. Not all of those supplies are still available, but the volume and range of distillery feeds have been substantially increased by the availability of co-products from bioethanol production. Most of the bioethanol produced in Europe is derived from


By Robin Crawshaw Although processing lifts the crude protein content, DDGS protein


has lower concentrations of several amino acids – particularly lysine – and the digestibility of some amino acids by pigs is lower than that of the protein in the parent cereal; again this particularly applies to lysine. Thus, although some research studies have found that DDGS diets supported similar performance to that of control-fed pigs, others have concluded that it would be prudent to add 0.1% crystalline lysine to the diet for every 10% inclusion of DDGS. Although much of the distillers’ solubles (CDS) produced during


wheat or maize, though minor quantities are obtained from blends that include other cereals. Potatoes are also used as a raw material, as is the ‘thick juice’ that is an intermediate product of sugar beet processing. From an animal feed viewpoint, bioethanol production enriches the nutrient concentration of the non-alcoholic fractions that are separated in the process and which are typically re-combined as DDGS before being marketed as feed. Bioethanol processing tends to increase the crude protein content of maize and wheat threefold, and to yield maize and wheat co-products with protein concentrations of approximately 31 and 36% of the dry matter (%DM) respectively. The oil content is increased to a similar extent, which takes the concentration in wheat DDGS up to 6%, and to 12%DM in the maize co-product. Both of these effects have a positive impact on the gross energy


content of the feeds and this outweighs the slightly negative effect of an increase in ash content. Thus the GE of maize and wheat DDGS is typically boosted from 18-19 MJ/kg DM in the grain to 21-22.5 MJ/ kg DM in the co-product. However, these feeds are increasingly being fed to growing pigs and the higher fibre content has a negative effect on digestibility. In wheat, this factor outweighs the higher GE value, such that the DE of wheat DDGS is lower than that of the whole grain. This effect is not seen with maize where the trebling of an innately rich oil content compensates for the reduced digestibility, and the DE value of maize DDGS is similar to that of the grain. The increase in ash content brings a significant benefit in terms of the phosphorus supply for pigs, viz: bioethanol processing increases the P content of the grain threefold and doubles its digestibility. Irrespective of these modifications to the composition, it is well


to remember that these co-products have a cereal heritage, and their use in diets for growing pigs may well necessitate amino acid supplementation.


PAGE 50 NOVEMBER/DECEMBER 2020 FEED COMPOUNDER


the distillation stage is evaporated and then recombined with the solid co-product fraction, the volume of CDS does vary, and consequently surplus amounts are sold separately in the form of a syrup. This syrup is typically rich in protein and it has proved to be a palatable material that can be easily incorporated into a mixer wagon on-farm. Different commercial products are available in Europe but they tend to have a broadly similar composition, though their dry matter contents vary to some extent. In contrast to whisky distilleries, where traditional procedures and


processes are specified by law, bioethanol producers have a free hand to modify the process at any stage. And this opportunity has been taken up before, during and after the fermentation process. Thus, upstream processing of the grain has removed fractions that would not be fermented, and this has thereby increased the efficiency of the operation. Additional nitrogen and a number of micronutrients have been added to the fermentation vat in order to improve the growth and functioning of the yeast. And downstream processing has been employed to remove oil and sometimes fibre from the solid fraction that has emerged from the fermentation chamber. All these additional processes have an impact on the composition


of the co-products that will potentially be marketed as feed, and, notably, high protein and oil-depleted variants of DDGS have been marketed. However, the proliferation of alternative processes has added some confusion to the terminology. De-oiled, semi-de-oiled and reduced oil versions do appear to require some numerical definition, while multiple high protein versions have been produced with significantly different protein and energy characteristics. Other variants have been described as ‘modified’ or ‘enhanced’ which may provoke questions about the nature and extent of such modifications and enhancements. Physical processing of DDGS – by grinding or extrusion – has also been shown to affect nutritive value, and this raises questions about the physical form of other variants. These many versions of DDGS have particularly been derived from the processing


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