Summary of the Value of Distillers Grains Plus Solubles for Feedlot Cattle

Authors: Rebecca L. McDermott, Research Technician and Graduate Student; Jim C. MacDonald, Professor; Galen E. Erickson, Professor, Animal Science, Lincoln. 

Summary with Implications

An analysis of over 6,100 head of finishing cattle across 50 experiments was conducted to determine the feeding value of full-fat and de-oiled distillers grains. This analysis was limited to studies where dry-rolled corn, high-moisture corn, or a combination of the two corn processing methods were displaced by 15% or more distillers grains. Dry distillers grains plus solubles (DDGS), modified distillers grains plus solubles (MDGS), and wet distillers grains plus solubles (WDGS) were evaluated as either full-fat or de-oiled. The feeding value of distillers grains was assessed relative to a corn-based control diet containing no distillers. Results indicate that removing fat from distillers grains reduces its feeding value by 8 percentage units, from 120.7% to 112.8%, across all distillers types. Additionally, feeding WDGS results in improved feed conversions compared to MDGS which is improved compared to DDGS.

Introduction

Corn-based ethanol production, particularly through the dry-milling process, is a vital value-added process for Nebraska and other corn producing regions. While recent innovations have introduced some changes, the core process of ethanol production from corn remains relatively straightforward. First, corn grain is ground, and then water and heat are added. Starch is converted to sugar enzymatically, and then the sugar is fermented to ethanol and CO2 by yeast. 

Once fermentation is complete, the ethanol is separated through distillation. The remaining byproduct is processed further by moisture evaporation, centrifugation, and sometimes drying, resulting in two co-products: distillers grains and distillers solubles. Distillers grains plus solubles (DGS), is a widely used livestock feed, especially for growing and finishing beef cattle, where it provides both energy and protein. Historically valued as a protein source due to limited quantities, DGS gained prominence in the early 2000s with the expansion of the ethanol industry, shifting its role towards displacing dietary energy, primarily from corn. Recent changes in processing have further influenced the composition and feeding value of DGS. In the traditional process, about 30% of the corn grain- mainly the non-starch components like protein, fiber, oil, and minerals- was concentrated in DGS, increasing these nutrients threefold. As a result, the DGS contained approximately 30-33% protein, 33-36% fiber (neutral detergent fiber), and 12-13% fat. Beginning in 2012, ethanol plants began extracting a portion of the corn oil during processing, reducing the fat content to 8-9%, which raised concerns about its impact on feeding value for cattle. Thus, the objective of this analysis was to evaluate the feeding value of full-fat and de-oiled distillers grains relative to a corn-based control diet, and to quantify their effects on intake (DMI) and gain (ADG).

Procedure

This dataset included a total of 50 experiments conducted at the University of Nebraska where distillers grains plus solubles (DGS) were fed to finishing cattle. The analysis was limited to studies that displaced dry-rolled corn, high-moisture corn, or a combination of the two corn processing methods with 15% or more DGS. These experiments were conducted over a 30-year span, from 1993 to 2023, and included over 6,100 head of cattle. Of the 50 experiments, 11 fed dry distillers plus solubles (DDGS), 12 fed modified distillers plus solubles (MDGS), and 38 fed wet distillers grains plus solubles (WDGS; Table 1). The DGS in these studies were either full-fat or had reduced fat content due to partial oil removal. Only studies conducted after 2012 fed reduced-fat distillers, however, many of those studies also included full-fat DGS in the same experiment. In each case, the feeding value of DGS was compared to a corn-based control diet that contained no distillers grains. The percent change in DMI and ADG was calculated by taking the difference between the DMI or ADG values for the DGS and control diets, divided by the control fed cattle’s DMI or ADG. Feeding value was calculated based on feed efficiency: specifically, the difference in gain: feed ratio between the DGS and control diets, divided by the control fed cattle’s gain: feed, and then divided by the inclusion rate of distillers grains since that was the only variable changed. In most studies, DGS replaced corn grain and supplemental protein was provided as urea.

Data were analyzed using the MIXED procedure of SAS with distillers type (DDGS, MDGS, or WDGS), fat content (full fat or de-oiled), and the interaction between distillers type and fat content included in the model.

Results

Distillers grains type had a significant impact on percent change in dry matter intake (DMI) compared to the corn control (P < 0.01; Table 2), whereas fat content did not have a significant effect (P = 0.13). Feeding DDGS and MDGS increased DMI by 6.0 and 3.4%, respectively, relative to the control (P < 0.01), while feeding WDGS had no impact on DMI (P = 0.65). There was a tendency for an interaction between DGS type and fat content for improvements in ADG (P = 0.09). Feeding full-fat DDGS and WDGS resulted in a greater improvement in ADG compared to their de-oiled forms. However, for MDGS the de-oiled form had a slightly greater improvement in ADG compared to its full fat form. This could be due to a greater increase in DMI for cattle fed the de-oiled form (5.22%) compared to the full-fat form (1.60%). Regardless of DGS type or fat content, feeding DGS improved ADG by approximately 8% compared to the corn control. 

Feeding DDGS has a feeding value of 113.4% of corn when full-fat, but only 103.4% when fed as de-oiled. For MDGS, the feeding value is 119.5% with full-fat and 114.7% when de-oiled. Feeding WDGS results in the highest feeding value, with 129.3% for full-fat and 120.4% when de-oiled. On average, removing fat from DGS lowered the feeding value by about 8 percentage units - from 120.7% to 112.8%. Despite a reduction in feeding value associated with fat removal, de-oiled DGS still improves ADG compared to a corn control and remains an excellent protein and energy source for finishing cattle. Consistent with many experiments, these data also support the idea that feeding DGS in the wet forms results in better feedlot performance (improved feed conversions) compared to partially dried (MDGS) and complete drying (DDGS). 

This summary also highlights that changes in the feeding value of DGS over time can be partly attributed to fat removal, however other factors may have changed as well. All DGS included in this analysis were from the traditional dry milling ethanol process.

While time is a confounding part of this summary, fat removal does likely explain the change in feeding value observed over the past decade as compared to the traditional feeding value of DGS in feedlot diets. 

Conclusions

For finishing cattle, WDGS provide the greatest feeding value, followed by MDGS and then DDGS. While fat removal from DGS, beginning around 2012, has lowered the feeding value by an average of 8 percentage units, de-oiled DGS remain a high-quality feed ingredient by improving gains compared to corn-based control diets.

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