Effect of Mixing Whole Shelled and Steam Flaked Corn in Finishing Diets on Feedlot Performance and Site and Extent of Digestion in Beef Steers

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Abstract
Beef steers were fed 85% concentrate diets in which the corn portion was comprised of mixtures of whole shelled (W) and steam flaked (SF) corn in the following ratios (as fed basis): 100W:OSF, 75W:25SF, 50W:50SF, 25W:75SF and OW:100SF. In Exp. 1 (150 Hereford steers, 152 d on feed), cattle fed the 75W:25SF and 25W.-75SF gained faster (P<.05) than those fed the OW:100SF diet, while remaining treatments resulted in intermediate gains. Feed efficiency was not different among treatments but tended to be better for the 25W:75SF treatment. Fecal pH was generally lower and fecal starch content higher as W corn increased in the diet, but variation was evident throughout the feeding period. In Exp. 2 (230 mixed breed steers, 191 d on feed), cattle fed the 25W:75SF and OW:100SF diets gained faster (P<.05) than those fed the 100W:OSF and 75W:25SF diets. Gains on the 50W:50SF diet were different (P<.05) from those on the 100W:OSF diet. Although not significant, feed efficiency was improved with the 25W:75SF and OW:100SF diets compared with other diets. No significant differences were observed in carcass characteristics in either experiment. Exp. 3 was a 5 X 5 Latin square design digestion trial with rumen-cannulated steers. Ruminal dry matter and organic matter digestion (lignin ratio) were higher (P<.05) for the OW:100SF diet than for the 100W:OSF, 75W:25SF and 50W:50SF diets but not different from the 25W:75SF diet. Ruminal starch digestion was also higher (P<.05) for the OW:100SF diet than for the 100W:OSF and 75W:25SF diets, but not different from other diets. Total tract dry matter, organic matter and starch digestion (Cr2C>3 or lignin ratio) generally increased with increased proportions of SF corn in the diet. Total volatile fatty acids (mmol/liter) were higher (P<.05) for the 25W:75SF diet than for other diets. Rumen pH at 3 h postfeeding was lower (P<.05) with OW:100SF and 25W:75SF than with 100W:OSF and 75W:25SF diets. Results suggest W corn can be partially substituted for SF corn in beef cattle finishing diets. Copyright © 1982. American Society of Animal Science . Copyright 1982 by American Society of Animal Science.