Effect on Rumen Volatile Fatty Acids and Rumen Microbial Dissimilation of Glucose-C14 of Corn Meal when Fed Exclusively and in Combination with Hay or Certain Additives

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Abstract
Comparisons were made of the effect of feeding various rations to Holstein heifers upon the rumen volatile fatty acids (VFA) and the dissimilation of C14 glucose by incubated rumen contents. Compared to a ration of alfalfa hay and corn (1:1), a ration of ground corn or ground corn and minerals resulted in a marked decrease and increase in the molar proportions of rumen acetate and propionate, respectively. A ration of flaked (steamed) corn and minerals accentuated these changes and, in addition, decreased the molar proportion of butyrate and increased the molar proportion of C6 and higher acids markedly. Addition of linseed meal to the latter ration increased butyrate at the expense of propionate. Dissimilation of C14-labeled glucose by incubated rumen contents demonstrated that the rations which induced a marked change in the molar proportions of rumen VFA also induced a marked change in rumen microbial metabolism.