ABSTRACT
Analyses of the rumen fluid of sheep fed on wheaten hay and on lucerne hay showed that characteristic changes take place in the composition of the mixture of volatile fatty acids in the rumen throughout the day.
The changes conform closely to those predicted from the composition of the mixture of fatty acids produced from the same two fodders in vitro. They support the view that propionic acid is relatively more rapidly absorbed than either acetic or butyric acid, and that the fermentation of these fodders in the rumen produces a mixture of the acids in which propionic acid forms a larger proportion than it does in the rumen fluid.
This latter claim has since been found only to be correct in certain circumstances. Under alkaline conditions absorption takes place to a varying degree, as found by Danielli et al. (1945). A number of factors have been shown to influence the extent of absorption when the rumen contents are alkaline Garrett, Gray & Rodda, 1949).
