Microbial Protein Synthesis in Steers Fed Processed Corn Rations

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Abstract
Four ruminally and abomasally cannulated Hereford steers were fed corn processed by one of four methods − dry rolling (DR), steam flaking (SF), propionic acid treated ensiled high moisture whole shelled (AHM) or ensiled ground high moisture shelled corn (GHM). The rations contained 43.8, 36.5, 59.3 and 96.9% of nitrogen as soluble nitrogen with DR, SF, AHM and GHM. Nitrogen intakes were 85.2, 76.1, 85.2 and 82.4 g/day while the abomasal nitrogen inflow was 77.1, 87.1, 85.2 and 105.3 g/day on the same treatments, respectively, indicating greatest recycling occurred with SF and AHM rations. Microbial nitrogen represented a greater percent (P<.10) of the abomasal nitrogen for the GHM ration than the AHM ration. But the microbial protein produced per 100 g dry matter digested (DMD) in the rumen indicated that energy from AHM was (P<.10) used most efficiently. A significant (P<.01) linear regression was observed between microbial protein synthesis/100 g rumen DMD and dilution rate per hour, indicating that turnover rate of rumen contents is an important factor in efficiency of microbial protein synthesis. Copyright © 1978. American Society of Animal Science . Copyright 1978 by American Society of Animal Science.