Changes in intraruminal function of sheep when drinking saline water.

I. A study was made of the changes in electrolyte concentrations and ruminal function which resulted from the provision of 1.3 7; sodium chloride solutions instead of fresh water to sheep consuming roughage rations in chaffed and in ground pelleted forms. 2. Significantly higher osmotic pressures were observed in the rumen fluid of the sheep drinking saline water, the change being especially marked when the ration was ground and pelleted. 3. Of the individual electrolytes measured, chloride showed a larger rise in concentration than did sodium plus potassium and it appeared that the sodium and chloride ions in the ingested saline water were differentially removed from the rumen. 4. Provision of 1.3 yo NaCl solution in place of fresh water resulted in greater voluntary intakes of fluid and consequently in greater flows of fluid through the rumen. 5. Based upon measurements of deoxyribonucleic acid and polysaccharide, there appeared to be a tendency for the total microbial populations in the rumens of sheep drinking 1.3 yo NaCl solution to be smaller than for the sheep drinking fresh water. 6. The total metabolic activity of the rumen flora, measured calorimetrically, was not appreciably changed when saline water was drunk and the chaffed ration eaten, but was significantly reduced when the ration was ground and pelleted. 7 . Adaptation of the rumen microflora to high concentrations of NaCl was demonstrated in animals accustomed to drinking 1'3 76 NaCl solution.