The measurement of production rates of volatile fatty acids in the caecum of the conscious rabbit.

1. The decrease in specific radioactivity of individual volatile fatty acids (VFA) after a single injection of tracer was monitored. The results obtained indicated the occurrence of a first-order process. 2. Regression analysis indicated the high flux of VFA through the caecal pool, equivalent to 30% of the maintenance energy requirement of the animal. 3. Interconversion of VFA was monitored, and results indicated substantial synthesis of butyric acid from acetic acid. 4. Results were obtained from animals on two dietary regimens, and these were compared with results reported for the other species.