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The effect of pH on the relative proportions of ruminal volatile fatty acids in sheep sustained by intragastric infusions

Published online by Cambridge University Press:  27 March 2009

N. A. Macleod ,
E. R. Ørskov  and
T. Atkinson
N. A. Macleod
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
E. R. Ørskov
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
T. Atkinson
Affiliation:
Rowett Research Institute, Bucksburn, Aberdeen, AB2 9SB
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Summary

Rumen pH was varied and controlled over the range 5·2–7·1 by manipulating the infusions of buffer solution to the rumen and by using an automated system of recording pH. The total concentrations of volatile fatty acids (VFA) in the rumen were not altered by changes in pH but there were changes in the relative proportions of VFA. As the pH of rumen liquor fell, the proportion of acetic acid increased, and the proportions of propionic and butyric acids decreased relative to their respective proportions in the infusate. At rumen pH of about 7·2 the molar proportions found were similar to the molar proportions infused while at pH 5·3 the molar proportion for acetic acid in the rumen was 100 mmol/mol higher than in the infusate. There was no apparent relationship between osmotic pressure and differences between VFA proportions in the infusates and in the rumen liquor.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 103 , Issue 2 , October 1984 , pp. 459 - 462
Copyright
Copyright © Cambridge University Press 1984

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References

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