The use of a by-product from ethanol and biofuel production, distillers dried grains with solubles (DDGS), in poultry feed can have a detrimental effect on the quality of the feed pellets, writes ThePoultrySite senior editor, Chris Harris.
Although the addition of DDGS to feed is both feasible and possible, the nature of the distillers grains alters the nature of the feed.
Research at Kansas State University set out to determine the effects of DDGS on the pellet quality and the pelleting performance when it is used in corn-soy diets.
At the recent International Poultry Science Forum in Atlanta, Georgia, Adam Fahrenholz, one of the researchers at Kansas State University said the quality of the pellet containing DDGS was important not only to the extent that the quality of the feed was affected, but also the impacts on production and the efficiency of the feed.
He said that the research showed that there was a decrease in the quality of the pellet as the proportion of DDGS in the feed increased. However, he added that there was no significant change in practical feeding quality and no effect on energy consumption in the feed mill.
Three studies were conducted: one where the nutritional value of the diet was not considered and another where DDGS was added to the feed at different levels, but the nutritional balance of the diet remained the same. In the third study the pellets were re-ground.
The study ensured that all batching and mixing, processing, and subsequent testing was completed at the Department of Grain Science Feed Processing Center at Kansas State University.
Observations on the viability of using DDGS were based on pellet durability index (PDI), energy usage measured in kilowatt-hours per tonne (KWH/tonne), production rate, and bulk density.
In the pilot experiment, DDGS was added to a non-nutritionally balanced diet as a replacement for corn at levels of 10, 20, 30 or 40 per cent.
Mr Fahrenholz said that the study showed there were no observed significant differences in pellet quality across all levels of DDGS addition, but there were differences in production rate and bulk density.
He said that the DDGS has a lower basic density compared to the corn or even soymeal and the effect on the rate of production was noticeable even with the same rate of screw.
He added that the DDGS also had a problem with "bridging" and there was also a difficulty when it cane to filling the trucks because of the way the DDGS acted when it was handled. However, he said, technically, it would be possible to have pellets made of 100 per cent DDGS.
In a second experiment, DDGS was added to a formulated diet at levels 10, 20, 30 or 40 per cent, and each was compared to a control diet. In this experiment, all ingredients were varied to maintain nutritionally similar diets.
Mr Fahrenholz said that in this second experiment, there was a large difference in production rate although there was no significant difference in energy consumption between the different treatments.
The research also showed significant differences in pellet quality, throughput and bulk density.
In the final experiment, DDGS was pelleted and then reground and added at levels of 10, 20 or 30 per cent to a formulated diet.
These diets were then pelleted and compared to a control diet with no added DDGS and to diets with unprocessed DDGS added at the same levels.
At levels above 10 per cent, the diets containing unprocessed DDGS had significantly lower pellet quality than the control, while the diets containing pelleted and re-ground DDGS showed no significant difference from the control at any level.
Significant effects were also observed for production rate, energy consumption, and bulk density.
Mr Fahrenholz said the researchers concluded that the use of standard DDGS in pelleted feeds is certainly feasible, and although pellet quality may be significantly lower for feeds containing DDGS, the practical value is unlikely to be affected.
"The dried distillers grains with solubles have to be ground, either at the ethanol plant or at the feed mill," he said.
"The pelleted and re-ground DDGS improved the pellet quality and improved the production rate as well as reducing energy consumption.
"It also increased the pellet bulk density and improved the handling quality of the DDGS."
