By Cheryl Anderson
DTN Staff Reporter
Researchers at Iowa State University recently conducted a feeding trial to examine whether smaller ground corn particle size could optimize starch digestibility and prevent the chance of acidosis in feedlot cattle fed a diet containing moderate amounts of wet distillers grains with solubles.
According to Erika Lundy, beef extension program specialist at the Iowa Beef Center at Iowa State University, the research (Influence of Corn Particle Size on Steer Performance and Carcass Characteristics When Fed Diets with Moderate Inclusions of Wet Distillers Grains plus Solubles) was an effort to examine two theories. First, researchers wanted to see whether feeding distillers grains can help moderate rumen pH, and secondly, if feeding a smaller corn particle size could result in an increase in cattle performance.
Another concern was the occurrence of acidosis, caused by a drop in the rumen pH, which causes the pH to become more acidic, Lundy explained. Many times acidosis will happen after cattle have excess or rapid exposure to corn, so the smaller the corn particle size, the quicker it is fermented in the rumen.
"If we take the corn kernel and grind it down, we're increasing the surface area," she said. "So then the microbes in the rumen can have access to the starch quicker and they break it down faster. That's what drives the decrease in the pH in the rumen."
Wet distillers grains are commonly fed in Midwestern feedlots, especially those located in close proximity to ethanol plants. The price of wet distillers is much cheaper than dry.
Lundy said that some previous research has shown that feeding wet distillers or even wet corn gluten feed can help moderate rumen pH and lessen the concern of acidosis. Since most of the starch from corn is removed during the ethanol fermentation process, the resulting distillers grains have little starch. So replacing a portion of the corn with WDGS further reduces the starch in feedlot diets.
Lundy explained that sub-acute acidosis can result in decreased performance, something that is always a concern for producers. If there is a continuous acidosis challenge, bigger decreases in performance can occur, even as high as 15%, she said.
"In that case we'll feed higher levels of hay and try to avoid the acidosis through better management to help reduce the risk of lost performance and ultimately lost dollars," Lundy said.
Severe acidosis can lead to such complications as liver abscesses or founder, she said, adding that preventing acidosis in diets is much easier and less costly than treatment.
FEEDING TRIAL
The trial used 500 stocker steers which were fed either a coarsely cracked corn control diet or a finely ground corn diet, both with 35% WDGS. Lundy said that the corn in the control diet was about 2,400 microns, just slightly lower than the industry standard. The finely ground corn was about 500 microns, with was fairly small compared to the industry norm.
"We fed 35% distillers grains because that was the industry standard at the time of the study," she said. "Our thought was that because distillers are low in starch, we can hopefully help moderate the rumen pH and keep it above the acidic conditions that would decrease performance."
In the end, the results of the experiment were contrary to the researchers' original hypothesis. The fine grinding of the corn did not improve feed conversion, but actually reduced dry matter intake and average daily gain compared to the coarsely cracked corn in the WDGS diets.
"We think that was because the cattle that were fed the fine corn treatment did have some subacute acidosis problems," Lundy said. "We didn't visually see any signs of acidosis, but based on the numbers we got of their performance, we think they did have some challenges."
The researchers found that although previous research showed that the rapid fermentation of finely ground corn contributed to acidosis in high grain diets, the reduction in DMI outweighed the benefits of greater starch digestibility because it limited performance.
Lundy said that the research team believes that their original theory could still be viable if they had had a little greater particle size for the fine-ground corn diet.
"We were really pushing the limits on that 500 micron fine-ground corn diet," she said. "I think if we would repeat the study with a larger particle size, it would be more effective."
She added that the team hopes to do some follow-up studies along that line, but is waiting on funding.
She said that the important thing learned after the trial was that the cattle fed the fine-ground corn definitely had an improved starch digestibility compared to the control diet.
"A lot of our producers are unaware of some of the performance they are giving up by not having their corn particle size ground fine enough," Lundy said. "But it becomes a challenge walking that tight line of how to optimize starch digestibility and not affect performance because of acidosis."
More detail on Lundy's research can be found on the official paper: http://bit.ly/…
Other researchers on the project were: Evan Vermeer-Midwest PMS, and Beth E. Doran, Daniel D. Loy and Stephanie L. Hansen, all of Iowa State University.
Cheryl Anderson can be reached at cheryl.anderson@dtn.com.
(AG/CZ)
© Copyright 2015 DTN/The Progressive Farmer. All rights reserved.