Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/31/2001
Publication Date: 2/1/2002
Citation: Dew, P. F., Drager, C. D., Brown, M. S., Cole, N. A. Effect of Degree of Corn Processing on Site and Extent of Digestion by Beef Steers. American Society Of Animal Science Southern Section Meeting. J. Anim. Sci. 80(S2):23 No.89. 2002. Interpretive Summary:
Technical Abstract: Five crossbred beef steers (average BW 336 kg) with cannulas in the rumen and duodenum were used in a 5 x 3 Incomplete Latin square to evaluate the effect of degree of corn processing on site and extent of digestion. Corn was processed by dry rolling (DRC) or steam flaking (SF) to a bulk density of 0.36 or 0.28 kg/L (28 [SF28] and 22 [SF22] lbs/bu, respectively) before inclusion into 90% concentrate diets fed every 2 hr. Enzymatically available starch for DRC, SF28, and SF22, averaged 25, 60, and 74% of the starch, respectively. Ruminal fluid pH was not influenced (P=0.15) by degree of processing (5.71 +/- 0.15); however, duodenal pH responded quadratically (P=0.03; 2.58, 2.22, and 2.51 +/- 0.17). Ruminal and total tract starch digestibility increased quadratically (P<0.08); ruminal and total tract starch digestibility were greater (15 and 5%, respectively) for SF28 and SF22 than DRC. Site and extent of OM digestion resembled changes in starch digestion. Postruminal starch digestibility (% of entry) was 49 greater (P=0.01) for SF28 and SF22 than DRC. Ruminal feed N digestibility and microbial efficiency (g of microbial N/kg of OM truly fermented) was lower (P<0.08) for SF28 and SF22 than DRC. Total tract N digestibility, and ruminal and postruminal P digestibility were not influenced (P>0.24) by degree of processing. A consistent effect of degree of processing on total tract P digestion was not evident (quadratic, P=0.09). Total tract ADF digestibility decreased linearly with an increasing degree of processing (P=0.02), whereas total tract NDF digestibility decreased quadratically (P=0.07). Increasing the degree of corn processing increased the extent of ruminal and total tract OM and starch digestion, and decreased the extent of ruminal N digestion and microbial efficiency.