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Digestion of finishing diets containing modified distillers grains plus solubles and condensed distillers solubles with and without oil extraction
Ethanol plants are currently removing a portion of corn oil, via centrifugation, from condensed distillers solubles (CDS) resulting in reduced fat distillers byproducts. Our objective was to determine the effect of reduced oil content on digestibility and rumen pH. Six ruminally fistulated steers (BW = 449 ± 20 kg) were utilized in a 5×5 Latin Square designed, 112-d metabolism study. Diets consisted of de-oiled and normal CDS fed at 27% inclusion, de-oiled and normal modified distillers grains plus solubles (MDGS) fed at 40% inclusion, and a corn-based control (CON). All diets contained a 1:1 blend of high-moisture and dry-rolled corn, 12% corn silage and 5% supplement. The fat content was 8.7% for de-oiled CDS, 15.4% for normal CDS, 9.2% for de-oiled MDGS, and 12.3% for normal MDGS. Therefore, dietary fat was 5.2% for de-oiled CDS, 7.0% for normal CDS, 5.9% for de-oiled MDGS, and 7.2% for normal MDGS compared to 4.0% for CON. Period length was 21 d which consisted of 16 d adaptation and 5 d fecal collection. Titanium dioxide was dosed intraruminally on d 10 to 20 as a marker to determine digestibility. Ruminal pH was measured continuously from d 17 to 21 with submersible, wireless pH probes. An oil concentration by byproduct type interaction was observed for fat intake (P = 0.07) and total tract fat digestibility (P = 0.03). Fat intake was the greatest for normal MDGS, intermediate for de-oiled CDS and normal MDGS, and the least for de-oiled CDS. Total tract fat digestibility was greater for normal CDS, intermediate for de-oiled and normal MDGS, and the least for de-oiled CDS. Greater oil concentration increased total tract fat digestibility for CDS (P = 0.02) but not for MDGS (P = 0.68). Treatment had no effect on DMI, OMI, and DM digestibilities (P > 0.27). No treatment difference was observed for total tract NDF digestibility (P = 0.11). There were no differences between feeding de-oiled and normal CDS for average pH (P = 0.74); however, feeding normal MDGS resulted in greater rumen pH than de-oiled MDGS (P = 0.06). Steers fed CDS or CON spent more time and area with a pH below 5.6 than steers fed MDGS (P < 0.02). Removing a portion of corn oil from CDS resulted in decreased fat digestibility in diets containing CDS, however this decrease was not observed in diets containing MDGS.
Keywords:
Centrifugation, De-oiled byproducts, Digestibility