[Emptying of the abomasum in adult ruminants]

In the adult ruminant, abomasal emptying is a permanent phenomenon depending upon meal volume. Intradian rhythm involving the motor pattern of the duodenum and circadian rhythm of unknown origin modulate the transpyloric flow rate. The fundic tone, antro-duodenal coordination and pyloric resistance regulate gastric outflow. The break-like function of the pyloric resistance involves chyme viscosity. Transpyloric flow rate is controlled by a hierarchy of extrinsic and intrinsic mechanisms triggered at the duodenal level. The vagus permanently inhibits the motility of the abomasum. A similar relationship is observed between the pyloric sphincter and duodenal motility. Removal of the pyloric ring leads to an increased food intake.