University of Minnesota (U of M) researchers have found that in-creasing moisture content of dried distiller's grains with solubles (DDGS) from 9% to 12% clearly and significantly reduced the flowability of the feedstuff.
However, the researchers were unable to find agents to help make the DDGS flow through bulk storage containers and transport vehicles without bridging.
DDGS handling challenges have caused some pork producers to stop using the product in swine diets.
Minnesota researchers designed a study to determine if adding flowability agents could make the DDGS flow more smoothly under practical, commercial conditions. The experiment was conducted at a dry-grind ethanol plant built in 2005.
Two sets of treatments made up of different flowability agents and moisture levels were simultaneously evaluated. Four flowability treatments were studied. A control group contained non-treated DDGS.
A grain conditioner called DMX-7 from Delst, Inc., is purported to control moisture migration, thus improving flowability. The other two flowability agents, added in the form of a very fine powder, were calcium carbonate, included at 2%, and a clinoptilolite zeolite, used at 1.25%.
The four flowability treatments were added to DDGS with 9% moisture, expected to flow readily; and DDGS with 12% moisture, expected to present poor flowability.
The ethanol plant produced DDGS at the two moisture levels and placed it in separate stockpiles in their warehouse.
About 5,000 lb. of DDGS was augered into a portable, on-farm grinder mixer, bypassing the grinding hammers, and the appropriate flowability agent was added. The mixer was equipped with a single vertical screw in the mixing hopper and an electronic scale for weighing mixer contents. Treated lots of DDGS were weighed and loaded into one of eight individual compartments in an auger-equipped feed truck.
Researchers simulated the transport of DDGS that often occurs in the commercial feed industry by sending the truck on a 300-mile trip over a weekend. Bumps in the road and vibrations during travel, along with cooling of the DDGS, all increase the chance that the DDGS will bridge and not flow freely. The same truck and operator were used on four different days to complete the experiment.
Researchers found flow rate was clearly poorer for DDGS with 12% moisture, compared with 9% moisture DDGS (Figure 1).
Similarly, the subjective flowability score was significantly higher for the wetter DDGS, illustrated in Figure 2. This indicates it was more difficult for the operator to unload compartments containing DDGS with 12% moisture, compared with those containing the drier DDGS.
None of the flowability agents significantly altered DDGS flow rate compared to the control treatment, which used no flowability agents (Figure 3). While there were numerical flow rate differences for various treatments, the researchers concluded these differences were not consistent enough to expect them to occur routinely.
The flow rate of DDGS treated with DMX-7 was significantly lower than that of the zeolite-treated DDGS, but neither of these was different than the additive-free control group.
Similar to the flow rate, subjective flow score was not consistently changed by the addition of the flowability agents tested in this research study (Figure 4).
The Minnesota researchers note this is the first attempt to test additives for improving flow rate of DDGS. They speculate that different inclusion rates or altogether different flowability agents should be tested. Their research work will continue to investigate what characteristics of DDGS will help predict flowability problems under commercial conditions.
Researchers: Lee Johnston, University of Minnesota, Morris, MN; Jerry Shurson, University of Minnesota, St. Paul, MN; John Goihl, Agri-Nutrition Services, Inc., Shakopee, MN. Contact Johnston by phone (320) 589-1711.