Effect of drying distillers grains on nutrient metabolism

Oct 7, 2011
by DTN

Wet distillers grains (WDG) are a cost-effective feedstuff for cattle producers living close enough to ethanol plants as wet distillers is sold at a much lower cost than its dry counterpart.

But recent research shows WDG have more benefits than just cost savings, according to Galen Erickson, beef feedlot extension specialist at the University of Nebraska-Lincoln (UN-L).

Researchers at UN-L are finding that wet distillers may improve cattle performance as well as lower greenhouse emissions.

Erickson and Terry Klopfenstein, professor at the UN-L Department of Animal Science, recently completed a study comparing the nutrient metabolism of WDG in beef cattle vs. dry distillers grains (DDG).

The idea for the study originated from early research on distillers grains that indicated WDG seemed to improve performance in cattle more than DDG.

“Wet distillers grains led to better performance than dry. Modified is intermediate between the two,” Erickson said. “The metabolism study was a way to get a feel for why that occurs.”

Part of that increase in performance may have to do with the increased energy value in WDG. Erickson said WDG has 130 percent to 135 percent of the energy value of corn, while dry has only about 112 percent of the energy value of corn.

For the study, Erickson and fellow researchers compared cattle on four diets: a corn-based control diet, WDG plus solubles, modified distillers grains (MDG) plus solubles, and DDG plus solubles. In the latter three diets, distillers grains were fed at 40 percent of the dry matter.

At the end of the trial, researchers found no differences in dry matter intake or dry matter, organic matter or fat digestibility. Erickson said the team was a little disappointed there was not more difference in digestibility. The hypothesis is that fiber digestibility may be the key.

“If we look at digestibilities, there was a trend for wet to be higher on fiber digestion than dry,” he said.

Since then, Erickson said there has been a follow-up study. Although not all data have been analyzed, he shared that there was a fairly large difference between the digestion of wet and dry. He said he is convinced that WDG has the best digestibility, but added that more trials are needed to statistically prove that difference.

The cattle in the study consuming the three distillers diets also had a greater intake of neutral detergent fiber compared to the corn diet because distillers grains have more fiber than corn, he said.

Another finding was that the cattle fed DDG had a greater pH than those on the other three diets.

“This tells me the digestion was slower and probably less than the other three, another indication that the fiber digestion in the rumen was less,” Erickson said.

He explained that when cattle consume feed, bacteria produce volatile fatty acids. If the cows digest more feed, the bacteria produce more acid. The higher pH for the cattle fed distillers is another indication that digestion was less or slower than the other diets.

In a separate performance study, cattle consuming distillers-based diets gained slightly more than 4 pounds per day, regardless of which type of distillers grains they consumed, but they had to eat more feed on the DDG to get the same gain. Cattle on the DDG diet had a conversion rate of 6.7 pounds of feed per pound of gain, Erickson said.

The cattle on the MDG diet ate a little less and gained the same, for a conversion rate of 6.3 pounds of feed per pound of gain. Those consuming WDG ate even less to get the same gain, at a conversion rate of 6.1.

“This is a perfect energy response,” Erickson explained.

“This illustrates that feeding distillers improves performance regardless of what type, but for finishing cattle, wet is better than dry. Modified is halfway in the middle,” he said.

Cattle fed the three distillers-based diets outperformed cattle fed the corn-based con trol diet, which had a gain of only 3.6 pounds per day and a conversion of 6.9.

Using wet distillers in cattle diets is beneficial for both producers and ethanol plants, Erickson said.

“If you can feed wet, especially in states like Nebraska, that is a big plus,” he said.

Erickson said there is more research planned in this area, especially using greater numbers of cattle. While the team has seen the difference in performance between DDG and WDG, they now want to look further into why that response is happening. — Cheryl Anderson, DTN