Álvaro García
Distillers’ grains consist of all the nutrients left once the starch in cereal grains is fermented to produce ethanol. Since starch constitutes over 2/3 of the grain composition, once used-up, all remaining nutrients (i.e. protein, fat, fiber, etc.) concentrate at least three-fold. Ethanol in the past was obtained predominately for the production of alcoholic beverages.
More recently, the increased use of ethanol in gasoline blends have made this co-product increasingly available, and as a result the need to find channels for its utilization. Because of the high nutritive value of the remaining nutrients, feeding it to livestock is undoubtedly the most efficient way of using them. In addition, incorporating co-products into livestock feed, reduces the carbon footprint and leads to greater overall food security.
During the production of alcohol, starch is fermented by specific enzymes to ethanol which is then removed by distillation. The remaining wet mash is then centrifuged to separate the solids from the liquid. The latter undergoes evaporation removing more water and leaving the “solubles” which then go through another centrifugation to separate some of their oil.
Once the oil is separated variable amounts of the remaining solubles are added back to the solids separated during the first centrifugation. In the US the proportions of solids and solubles added back are regulated by law, a restriction that however does not occur in Europe. This results in variability in the composition of the distillers’ grains originated from different European distilleries that produce alcoholic beverages.
Although in the US corn is the predominant grain used for alcohol production resulting in a corn distillers’ grains co-product, other countries such as Canada, Germany, and the United Kingdom also use wheat as a source of fermentable starch. While the use of corn DDGS has been extensively studied in the US, there is not much research conducted with wheat DDGS.
Studies in Canada and Germany have shown that the inclusion of between 15 and 17% wheat DDGS in the diet did not negatively affect milk production. There had not been however studies with wheat DDGS produced in Europe until recently.
The opening of two biorefineries in the UK in 2010 and 2013 (annual combined capacity of 850,000 tons of wheat DDGS) sparked the interest to conduct some cattle feeding trials. As a result, a group of local researchers (Garnsworthy et al., 2020) conducted an experiment to measure the responses to wheat DDGS inclusion in diets of high-producing dairy cows.
The authors designed two experiments, testing two batches of wheat DDGS each from a different distillery at four feeding amounts fed to high producing dairy cows. Wheat DDGS replaced soybean and rapeseed meals in the diets. One of the wheat DDGS had lower solubles concentration, which decreased its metabolizable energy. Its inclusion had to be then under 20% of the diet dry matter (DM) to avoid reducing intake and milk production.
The other batch of wheat DDGS had higher solubles and higher metabolizable energy and could be added at 22.5% of the diet DM without affecting intake or production. All diets were balanced for metabolizable energy (ME) and protein (MP), and in experiment 2, for minimum starch and saturated fat.
- Experiment 1: 44 cows were fed diets containing wheat DDGS replacing soybean and rapeseed meals at 0, 0.8, 16.0 and 24.0% of the diet DM.
- Experiment 2: 40 cows were fed diets containing wheat DDGS replacing soybean and rapeseed meals at 0, 7.5, 15.0 and 22.5 g/kg of the diet DM.
Diets were formulated based on the following feedstuffs: grass silage, corn silage, wheat silage, wheat straw, wheat DDGS, soybean meal, rapeseed meal, rolled wheat, ground wheat, sugar beet pulp, protected fat, molasses, urea, vitamins and minerals.
Inclusion of wheat dried distillers’ grains with solubles and DM intake
In experiment 1 there were no effects on DM intake (29 kg/day) and milk yield (42.3 kg/day) with wheat DDGS inclusions of up to 16.0% of the diet DM. When fed at the rate of 24.0% however, both intake and production were lower than the control, probably a result of the low proportion of solubles and energy in this batch of wheat DDGS. There was no effect of wheat DDGS inclusion on milk components, but milk urea nitrogen was greater for wheat DDGS inclusion levels of 0 and 8.0% compared with 16.0 and 24.0%.
In experiment 2 DM intake (22.4 kg/day) and milk production (32.1 kg/day) were not affected by wheat DDGS inclusion up to 22.5%. The ME of wheat DDGS, determined in vivo was 12.1 MJ/kg DM (2.89 Mcal) in experiment 1, and 13.4 MJ/kg DM (3.2 Mcal) in experiment 2.
Importance of the origin of wheat dried distillers’ grains with solubles
Results of this experiment clearly show the importance of taking into consideration the origin of wheat DDGS when balancing diets for dairy cows. In countries where there is no regulation with regards to the amounts of solubles added back to the centrifuged mash, there can be significant differences in the energy content of wheat DDGS as a result of differences in oil concentration.
In the practice, and under farm conditions where cows are fed ad libitum these differences might not be that easy to detect, unless there is very close monitoring of feed intake. It was concluded however that the optimum inclusion level of wheat DDGS to be at least 22.5% DM in diets balanced for minimum starch and saturated fat as well as ME and MP. These values are very similar to the 20% corn DDGS suggested in earlier studies in the US.
Reference
Philip C. Garnsworthy, Michael Marsden, Jennifer R. Goodman and Neil Saunders. 2020. Inclusion of Wheat Dried Distillers’ Grains with Solubles from Bioethanol Plants in Diets for Dairy Cows. Animals, 11, 70.
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