WOOSTER, OHIO — Distillers grains were not common feedstuffs 10 years ago. But today they’re routinely included in cattle-finishing diets at levels that can boost beef quality grades, according to a Certified Angus Beef LLC news release.

When "wet distillers grains plus solubles" (W.D.G.S.) are fed at moderate levels, marbling scores increase, said Chris Calkins, meat scientist, University of Nebraska. "It tends to be a quadratic effect," he added. "If you do not feed any distillers grains, you get a given level of marbling. As [W.D.G.S.] in the diet increases, we see an increase in marbling score up until about 30% to 40%; beyond that the benefits to marbling tend to disappear."

Last summer at national animal science meetings, Mr. Calkins presented a meta-analysis of studies looking at W.D.G.S. feed effects. Larry Corah and Mark McCully of Certified Angus Beef LCC (C.A.B.) cited that presentation in a recent research review of factors responsible for a spike in beef quality grades. Through July 2009, 60.1% of cattle in the nation’s harvest mix were grading U.S.D.A. Choice, a 7.5-percentage-point leap in just two years.

Representing an abrupt departure from the 30-year decline in grades, the recent turnaround may be partly explained by judicious use of W.D.G.S. "marbling increases, but if you get the levels too high it starts to trail off," Mr. Calkins said.

The data he presented showed a marbling score of 518 for animals fed no W.D.G.S. The score increased 14 to 15 points, up to 533, for animals fed W.D.G.S. at 20% to 30% on a dry-matter (D.M.) basis. "That seems to support earlier findings that at inclusions above that 30% to 40%, distillers can actually hurt quality grade," Mr. Corah said. "Fortunately, a large majority of feedlots are using the byproducts at a fairly low rate."

According to a 2007 survey, it was estimated most feedlots used W.D.G.S. at 16.5% of diets, but that has likely jumped in recent years due to availability. The marbling score increase is probably related to fat content of the feedstuffs, Mr. Calkins said. "When you make ethanol from corn, you’ve basically driven off about two-thirds of the components," he says, noting that both ethanol and CO₂ are produced from the starch that comprises two-thirds of corn grain. "So everything else is concentrated by about three-fold. That includes the fat content."

He added this higher-fat diet promotes marbling development. Theoretically, it can increase external fat as well, but Mr. Calkins said that’s a fairly small shift. "I don’t think there’s a big worry for producers in terms of cutability issues with using wet distillers grains," he added.

W.D.G.S. also seems to increase D.M. intake, especially in starter rations. One Nebraska study shows nearly a 30% increase. "It’s a highly effective feedstuff in terms of increasing average daily gain and dry matter intake," Mr. Calkins said.

The only drawback to feeding W.D.G.S. from a meat-quality standpoint seems to be the increase in polyunsaturated fats. They can cause discoloration and off-flavor more quickly than other fats when exposed to oxygen. "That’s dose-dependent," he said. "In other words, the more distillers we feed, the bigger issue it can become."

Feeding W.D.G.S. at 20% to 30% should pose fewer challenges for retail beef than those higher percentages. However, at any level the problems can be easily managed by supplementing diets with vitamin E, Mr. Calkins said.

Although the W.D.G.S. effect on marbling score seems slight, Mr. Corah estimates it accounts for around 5 percentage points of the grade increase. That’s based on applying the shift to packing data, where many cattle grades sit on the line between Choice and Select or low- and premium Choice.

"That’s going to increase the proportion of cattle that could conceivably qualify for the [Certified Angus Beef] brand," Mr. Calkins said.