Cineradiographic Studies of Gastric Motility in the Great Horned Owl (bubo Virginianus)

Gastric motility in the Great Horned Owl (Bubo virginianus) has been the subject of few previous studies. A gastroduodenal contraction sequence beginning with the glandular stomach (proventriculus), then the muscular stomach (gizzard), and lastly the duodenum was observed radiographically by Reed and Reed (1928) and Kostuch and Duke (1975). Contractions arise near the isthmus in the muscular stomach and move around the greater curvature to the pyloric area. Kostuch and Duke (1975) also studied intragastric pressures telemetrically and described three phases in the frequency and amplitude of gastric motility during the digestion of a meal. The apparent purpose of each phase was postulated but not determined experimentally. That these phases were initiated upon eating, or even upon seeing food, was demonstrated by Duke et al. (1976a) using strain gauge transducers implanted on the muscular stomach to monitor gastric motility. Gastric contractions which formed the gastric contents into a pellet were described from serial radiographs by Grimm and Whitehouse (1963) and via fluoroscopy by Reed and Reed (1928), but pellet egestion was not observed in these studies. Intense electrical and contractile events occurring in the esophagus, muscular stomach, and duodenum preceding and during pellet egestion have been detected by implanted electrodes and strain gauge transducers and recorded (Duke et al. 1976b). They were correlated with simultaneous radiographic observations of gastric motility. Other gastrointestinal motility studies of raptors were performed by Dedic (1930) on European Goshawks ( Accipiter gent&s) and Mangold (1911) on a Common Buzzard (Buteo buteo) . As much remains to be learned about gastric digestion in owls, we undertook to (1) further characterize the phases of digestive motility in the muscular stomach by another method, viz. cineradiography, (2) help determine the function of each phase by removing and examining gastric contents during these phases, and (3) observe pellet egestion and relate the gastric contraction pattern during the egestion process to patterns observed during other phases in digestive motility.