USE IN FEEDLOT CATTLE
Feeding Value

The first units of co-products added to a ration are primarily used to replace protein from urea or natural protein sources in the ration. Subsequent additions of co-products to the ration replace corn and other grains as energy sources. Feedlot diets that use DGS at levels less than 15 to 20% of diet DM serve as a protein source for the animal. Conversely, when DGS is added above these levels, the beef animal utilizes the DGS as an energy source.

The feeding value of DGS and CGF is dependent on whether the co-products are fed wet or dry and the level of dietary inclusion. Although the feeding value of WCGF is better than corn (100 to 112% the feeding value of corn), the feeding value of DCGF is 88% of dry rolled corn (DRC) when fed at 25 to 30% of diet DM (Green et al., 1987; Ham et al., 1995).

The majority of the research on distillers grains as a feed source has been conducted on finishing cattle. Experiments evaluating the use of wet distillers co-products in ruminant diets are available (Buckner et al., 2007a; Corrigan et al., 2007b; DeHaan et al., 1982; Fanning et al., 1999; Farlin, 1981; Firkins et al., 1985; Larson et al., 1993; Luebbe et al., 2007; Trenkle, 1997a; Trenkle, 1997b; Vander Pol et al., 2004; Vander Pol et al., 2005a). Feeding WDGS results in better performance than DDGS (Table 3).

In studies with finishing cattle, the replacement of corn grain with WDGS consistently improved feed efficiency (Figure 3). Figure 4 summarizes University of Nebraska studies conducted on WDGS with feeding value expressed relative to corn.The feeding value of WDGS is consistently higher than corn. These studies suggest a 31 to 43% improvement in feed efficiency when WDGS replaces intermediate levels of DRC (15 to 40% of diet DM).The WDGS replaced corn in the diet.The feeding value at low levels (less than 15%) is approximately 145% the feeding value of corn. When higher levels of WDGS are used (greater than 40%), the feeding value was still greater than corn. Replacing DRC with WDGS results in a quadratic improvement in average daily gain (ADG) (Figure 5).The optimal biological response in ADG was at 30% WDGS inclusion.

Huls et al. (2008) evaluated modified distillers grains plus solubles (MDGS; 42 to 48% DM) at 0, 10, 20, 30, 40, and 50% of diet DM, which is potentially different than traditional WDGS (32 to 35% DM) because it is partially dried. Carcass adjusted final body weight (BW) and ADG responded quadratically (P < 0.01) as MDGS inclusion increased (Table 4). Cattle fed 20% MDGS produced the greatest ADG. Feed conversion improved linearly (P < 0.01) with optimum conversion seen when cattle were fed 50% MDGS. Calculated feeding value of MDGS relative to HMC/DRC was highest for 10% MDGS and decreased as MDGS treatment increased to 50% of diet DM (123 to 109% the feeding value of corn, respectively). Carcass weight and USDA calculated Yield Grade responded quadratically (P < 0.05) as MDGS inclusion increased in the diet with 20% MDGS cattle having the heaviest carcasses and greatest Yield Grade. Daily gain was greatest at 20 to 30% MDGS inclusion, and feed to gain (F:G) was lowest at 40 to 50% MDGS dietary inclusion.

Therefore, we would recommend feeding 20 to 40% of diet DM as modified wet distillers grains plus solubles to optimize performance. Buckner et al. (2007d) conducted a 145-day feedlot finishing study to evaluate 0, 10, 20, 30, and 40% dietary DM inclusion of DDGS in corn-based diets on steer performance. There was a quadratic response in performance. The 20% DDGS diet had the most improved performance when compared to a cornbased diet, with a feeding value of 126% the value of corn (Table 5). However, all DDGS levels had improved F:G and feeding value relative to the corn control diet. The biological optimum level of DDGS to feed with DRC and high moisture corn (HMC) is less than with WDGS.The biological optimum levels for the dry and wet DGS are 20 and 30-40%, respectively.

Experiments evaluating the use of WCGF replacing DRC or HMC in feedlot diets are available (Buckner et al., 2007a; Herold et al., 1998; Loza et al., 2007; Richards et al., 1995; Scott et al., 2003; Scot et al., 1997). Distinct differences exist for WCGF, even within companies, due to plant-to-plant variation. Stock et al. (1999) divided WCGF into two main categories, depending on the ratio of steep to bran. Based on differences in the amount of steep added,WCGF has 100 to 109% the feeding value of DRC when fed at levels of 20 to 60% of diet DM (Stock et al., 1999).The higher feeding value (and protein) is associated with increases in steep added in WCGF. Feeding WCGF results in better performance than DCGF (Ham et al., 1994). In studies with finishing cattle, the replacement of corn grain with WCGF consistently improved feed efficiency (Figure 6). Replacing DRC with higher feeding value WCGF in feedlot diets will linearly improve ADG (Figure 7).

The improved animal feeding performance from co-product feeds translates into improved quality grade for steers fed co-products compared to grain. (Bremer et al., 2007). Since the co-product diets have improved feeding values relative to corn, the cattle gain weight quicker than corn fed feedlot cattle. Therefore, these cattle require fewer days on feed to reach the same backfat and marbling endpoints. Co-products-fed cattle consuming intermediate levels (10 to 40% diet DM) of WDGS or WCGF for the same number of days on feed (DOF) as conventional corn fed cattle will be slightly fatter (Figures 8 and 9) and have more marbling than corn-fed cattle (Figures 10 and 11). The improved marbling is due to improved daily gains. Feeding diets that help cattle fatten more rapidly (i.e. co-products diets) will improve the Quality Grade of feedlot cattle.

In certain production situations, light weight (less than 750 lb) finishing cattle may need to be supplemented with UIP (bypass) protein to meet metabolizable protein (MP) requirements. Wet or dry DGS is an excellent source of UIP. The values obtained from feeding trials for UIP are shown in Table 6. Wet grains were compared to dry grains and the value of the protein was similar (Table 7). This suggests that the high escape protein value of DGS is due to the innate characteristics of the protein and not to drying or moisture content, and does not appear to be influenced by acid-detergent insoluble protein (ADIN), which is a common measure of heat damaged protein.

Dry distillers grains contain approximately 65% UIP (% of CP), consequently diets that include dried distillers grains fed as an energy source are commonly deficient in degradable intake protein (DIP) but contain excess MP. Cattle convert excess MP to urea, which is potentially recycled to the rumen and can serve as a source of DIP. Vander Pol et al. (2005b) fed DDGS to finishing cattle at either 10 or 20% of diet DM. No advantage was observed between cattle supplemented with urea, (DIP) or not, suggesting recycling was occurring in finishing diets supplemented with 10 or 20% DDGS. However, some numerical differences suggested a conservative approach would be to follow NRC (1996) guidelines for DIP supplementation if DGS are provided at less than 20% of diet DM.

For more information or to request additional copies of this manual, contact the Nebraska Corn Board at 1-800-632-6761 or e-mail k.brunkhorst@necorn.state.ne.us.

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For more information on the feeding of corn milling co-products to beef cattle
and information contained in this manual, contact:
Dr. Galen Erickson, University of Nebraska-Lincoln, Department of Animal Science Room C220, Lincoln, NE 68583-0908, 402-472-6402

Date published: August, 2007