July 18, 2006
US packers see decreased marbling with distillers grains feed
As US ethanol production from corn increases and cattle feeders use the rising supply of distillers grains in feed rations, packers are noticing a correlating decline in carcass marbling scores, trade and packer sources said.
However, it's not clear that using distillers grains is reducing carcass grades, and if it is a factor, the decline is small, nutritionists said. Some say it can increase marbling if its percentage of the ration is not too large.
"There is a trend for grade to be improved up to (about 30 percent of dry matter in the feed)," said Frank Goedeken, nutritionist for several feedlots, of Dodge City, Kansas. The added rate of gain brought on by using distillers grains means more fat is being deposited, and when cattle are sold at heavier rates, they're going to grade better.
Degradations in grading usually come from parts of the US that are close to the ethanol plants and the product is cheaper, Goedeken said. In western Kansas, the practice usually is to feed at about 10 percent of dry matter.
Available research points to distillers grains being only one of several factors such as genetics and grower practices that can reduce marbling scores. The only difference is that increased use of these products is a recent trend, and the ration change has taken place over a shorter period of time, making it more noticeable.
"We have seen a difference," said Joe Meng, vice president of animal science, health and welfare for Creekstone Farms Premium Beef LLC, Arkansas City, Kansas. And while long-term declines can't be pinned on distillers grains alone, "there's every reason to believe removing the starch from the corn affects marbling," he said.
When corn is used to make ethanol, the process leaves about a third of it, or about 18 pounds, as distillers grains, said Chris Reinhardt, extension feedlot specialist at Kansas State University, Manhattan, Kansas.
Distillers grains consist mostly of digestible fibre, protein and fat, the sources said.
Reinhardt, along with Larry Corah and Mark McCully of Certified Angus Beef, compiled about 13 published university studies on cattle feeding practices to see if they could find any general tendencies that would affect marbling, he said. What they found was that there is no single factor that affects marbling to any great degree.
Instead, several factors may have an additive effect on carcass grade, Reinhardt said. These included genetics, implants and age, along with various feeding practices like the use of distillers grains.
"People have taken it out of context," Reinhardt said. Each of the factors affecting marbling had a "minimal" effect, according to the studies.
In the case of distillers grains, there was "a slight depression in marbling, but only if it was fed at levels above 30 percent of the diet's dry matter," Reinhardt said. This is at the upper end of the 10 percent to 40 percent of dry matter that is commonly fed.