The rapid expansion of the U.S. ethanol industry has made dried distillers grains with solubles (DDGS) readily available for livestock feed. One challenge associated with DDGS feeding relates to soft fat that occurs in pork carcasses when high levels of DDGS are included in swine diets.
Soft fat creates problems for processors when they slice bacon and for consumers that discriminate against pork products that have an oily or soft appearance. The soft fat results from the high levels of corn oil present in DDGS.
The high cost of fossil fuels has forced many ethanol plants to seek alternatives for drying distillers grains. One alternative used by some ethanol plants is to burn the solubles generated during ethanol production as fuel for their dryers. Burning the solubles to dry the wet distillers grains reduces the amount of natural gas needed in the drying process and results in a livestock feed called Low-Solubles Dried Distillers Grains (LS-DDG). LS-DDG has lower fat content than typical DDGS (7.95% vs. 8.87%).
To better understand and compare how pigs respond to LS-DDG vs. typical DDGS, an energy balance trial and a growth performance trial were conducted by University of Minnesota researchers.
In the energy balance trial, it was determined that metabolizable energy content of LS-DDG (1,342 kcal/lb. dry matter) is essentially equal to the DDGS (1,344 kcal/lb. dry matter) evaluated in this study. In addition, nitrogen digestibility (an indicator of protein digestibility) of diets containing high levels of LS-DDG was marginally better than diets with similar concentrations of typical DDGS.
Increasing dietary LS-DDG from 0 to 40% showed no decline in nitrogen digestibility, but increasing DDGS to 40% of the diet elicited a 2.2% drop in nitrogen digestibility. Therefore, LS-DDG can be included in diets for growing-finishing pigs without compromising energy density of the diet, and there may be some improvements in protein digestibility of LS-DDG-containing diets.
In the second experiment, diets contained 20% LS-DDG or 20% DDGS were compared to typical corn-soybean meal diets with no added ethanol by-products (Table 1).
No differences in growth rate or feed intake were found for pigs fed the experimental diets. The often-seen depression in dressing percentage was observed for LS-DDG- and DDGS-fed pigs. Carcass lean was higher for LS-DDG-fed pigs compared to those fed DDGS.
Belly firmness was measured by draping a belly over a suspended bar (see photo). A firm belly will not droop as much as a soft belly. Pigs fed LS-DDG had firmer bellies than the DDGS-fed pigs, but they were slightly softer than pigs fed the control diet. These differences in belly firmness are likely due to the lower iodine value of LS-DDG bellies compared with DDGS bellies.
Results of this investigation suggest that LS-DDG is a valuable feed ingredient for growing-finishing pigs. Use of LS-DDG should help reduce some of the less desirable carcass traits observed when high levels of DDGS are fed during the late finishing period. Financial support from the Agricultural Utilization Research Institute and donation of LS-DDG and DDGS from the Corn Plus ethanol plant in Winnebago, MN, made this research possible.
Researchers (all from the University of Minnesota): Lee Johnston and Jon Anderson, West Central Research and Outreach Center; Roberta Amara and Jerry Shurson, Department of Animal Science; and Sam Baidoo, Southern Research and Outreach Center. Contact Johnston by phone at (320) 589-1711 or e-mail [email protected].
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