SOLUTES IN THE RUMEN OF THE SHEEP

Abstract

The osmolality and specific conductivity and the concentrations of sodium, potassium, ammonium, volatile fatty acids, total nitrogen, dry weight and ash were determined in the rumen liquor of sheep that had been without feed or water for 18 hr. The liquor was significantly hypotonic to blood plasma. The fasting levels of the rumen osmolality and specific conductivity, the dry weight content and the concentrations of sodium and potassium appeared to be characteristic of the individual animal. A series of experiments was carried out on two sheep to determine the changes in the rumen constituents following the giving, or prolonged withholding, of feed and water. The rumen contents remained hypotonic during a 3 days' fast. Injection of 1500 ml. water diluted the rumen contents and it took more than 10 hr. for normal conditions to be restored. When the animals were fed, the rumen contents rapidly became hypertonic, largely due to the ingestion of potassium salts and the production of volatile fatty acids; unexpectedly it was found that the ingestion of a dry ration containing NaCl did not greatly affect the concentration of sodium in the rumen contents. Even when the animals drank after eating, the subsequent decline in the concentration of the total rumen solutes was a gradual process. © 1965 The Physiological Society