Gastric emptying rate was calculated from dye dilution and was measured as the net flow over periods of 5 days through an electromagnetic probe inserted into a T-cannula, 5 cm beyond the pylorus in conscious hay-fed sheep. The net aboral flow was related to the motor activity of the antrum and duodenal bulb which was recorded via chronically fixed strain-gauge transducers. Nichrome wire electrodes were also implanted in order to quantify the electrical activity of the musculature associated with the abomasal outflow in sheep sustained on a liquid diet infused at fixed rates. 2. The abomasal outflow occurred as gushes of 2.1-9.2 ml associated with antroduodenal contractions during 90-95% of the recording time. In the sheep eating 0.7 kg/day hay, the daily outflow of chyme was 5.1 l which increased to 7.5 l of less viscous chyme when the sheep was fed 1 kg/day lucerne hay. During gastric infusion of 3.9 and 7.9 l of the liquid diet, the outflow was 5.7 and 8.3 l/day respectively of low-viscosity chyme propelled as gushes of 5.9-6.9 ml during 95% of the recording time. 3. Increasing the viscosity of the liquid diet with guar-gum caused a reduction in both antroduodenal motility and flow. Dilution of the liquid diet with saline doubled the flow as a result of an increase in the amplitude of the antral contractions. Circadian variations in outflow were also related to concomitant variations in antral motility. 4. It is concluded that the minute-to-minute flow rate of chyme through the pylorus could be satisfactorily measured at the duodenal bulb level and related to the motor activity of the antrum and duodenum. The rate of abomasal outflow depended primarily upon the strength of antral contractions, while the viscosity of the chyme also appeared capable of exerting a major influence on the outflow rate.
