Gary E. Duke

Gastric digestion in some raptors

Abstract 1. 1. Gastric digestion of mice in falconiforms is apparently more thorough than it is in strigiforms because the proportion of the food consumed that reappears as a pellet is lower in the former than in the latter. 2. 2. This difference is principally due to a more thorough corrosion of the bones in the food by Falconiformes, i.e. there is a smaller proportion of bone in falconiform pellets. 3. 3. Falconiform gastric juice contains considerably more hydrogen ion than strigiform and this probably accounts for the greater bone corrosion by falconiforms. 4. 4. Gastric proteolytic activity is about equal before and after eating in both orders of raptors. 5. 5. The meal-to-pellet interval is also about equal between the two orders. 6. 6. The pH and proteolytic activity of the gastric juice of raptors were in general significantly bifferent from these values in domestic ducks and turkeys, but the values found for poultry agree with published data.

Meal to pellet intervals in 14 species of captive raptors.

Abstract 1. In owls, meal to pellet interval was directly related to meal weight and owls normally cast 1 pellet per meal; egestion of pellets in hawks apparently was associated with “lights-on” in the holding rooms regardless of quantity eaten and hawks normally egested less than 1 pellet per meal. 2. All of the smallest raptors digested meals and egested pellets more rapidly than the larger raptors. 3. The correlation between meal weight and pellet weight was only slightly better for owls than for hawks, but, because owl pellets contained more of the bones of their prey, they represented a greater proportion of the meal from which they originated.

Food intake, gastric secretion, and motility as affected by avian pancreatic polypeptide administered centrally in chickens

The effects of intracerebroventricular (ICV) injections of avian pancreatic polypeptide (APP) on food intake, gizzard motility, gastric secretion volume, pH, and pepsin concentration was investigated using 16-20-week-old Single-Comb White Leghorn hens. Birds were stereotaxically cannulated in the right lateral ventricle. In addition, a strain gauge was attached to the gizzard to measure motility and a polyethylene cannula was implanted into the caudoventral margin of the proventriculus to collect glandular secretions. All birds were fasted for 18 hr prior to the injection of APP. In Experiment 1 food was made available immediately following the injection of APP while in Experiment 2 food was withheld for an additional one hr post-injection. The ICV injection of APP significantly increased food intake but had no significant effect on gizzard motility, gastric secretion volume, pH, or pepsin concentration in birds given access to food immediately after injection. In birds which remained fasted after injection, pepsin concentration was decreased by APP injection, but gizzard motility, gastric secretion volume, and pH were not affected. Because ICV injections of APP significantly increased food intake and, in fasted birds, decreased pepsin concentration, it appears that APP is involved in the central nervous system control of food intake and pepsin secretion in the domestic fowl.

Colonic motility in domestic Turkeys

This study was performed to determine (1) if electrical slow waves could be recorded from the colon of turkeys, and (2) how ingesta moves into and through the colon despite colonic antiperistalsis. Electrical activity and contractile forces were monitored via implanted bipolar electrodes and strain gage transducers (SGT), respectively. Two types of slow waves, small (sSW) and large (lSW) were recorded simultaneously. The former were correlated with antiperistaltic contractions observed radiographically and with small contractions recorded with SGT, the latter were correlated with large contractions recorded via SGT. The sSW had higher frequencies distally than proximally while the frequency gradient for the lSW was just the opposite. The sSWs were believed to be involved in regulation of antiperistalsis while the lSW were believed to be involved in regulation of the large contractions which, on the basis of the lSW frequency gradient, appeared to be peristaltic and to be primarily responsible for aborad movement of colonic digesta. The small contractions were believed to be responsible for reflux of urine from the cloaca into the colon and ceca and for cecal filling.

Food consumption and energy, water, and nitrogen budgets in captive great-horned owls (Bubo virginianus).

Abstract 1. 1. The metabolizability of diets of laboratory white mice and 1-day-old domestic turkey poults by adult great-horned owls averaged about 67·9 and 71·2 per cent respectively. 2. 2. The metabolizable energies of these two diets were 4304 and 4151 cal/g respectively. 3. 3. The owls ate about 26·5 g/kg (dry weight) of each diet per day. 4. 4. The owls consumed an average of 4·4 per cent of their body weight in water per day. All water consumed was in their food. Sensible water losses amounted to slightly over 50 per cent of water consumed for both diets.

Gastroduodenal electrical activity in turkeys

Bipolar Ag/AgCl electrodes were implanted in the stomach and duodenum of 21 turkeys to study electrical activity in those organs. Intraluminal pressure changes were also monitored. For comparative purposes, electric slow waves were recorded from the ileum of one dog. Slow waves were not observed in the recordings from the stomach of turkeys. Although slow waves were recorded from the duodenum of turkeys, the waves were observed to wax and wane and were possibly not the major regulators of duodenal contractile activity. Several bursts of action potentials and several contractions usually occurred in the duodenum during one slow-wave cycle. Duodenal motility appeared to be totally coordinated with the gastric cycle. Impulses conducted over intrinsic nerves from a gastric pacemaker (15) were proposed as a possible mechanism for initiating and coordinating gastroduodenal motor activity.

The influence of the stomach on crop function and feeding behavior in domestic turkeys

We tested the hypotheses that motility of the crop and muscular stomach are coordinated and that the stomach exerts primary control over crop filling and emptying in domestic turkeys. Simultaneous recordings of motility of the crop, esophagus, and stomach with implanted strain gauge transducers and visual observations of food passage using image intensification radiography revealed an inverse relationship between the frequency of stomach and crop contractions. Artificially filling the stomach of a fasted turkey with a food slurry prior to feeding did not increase crop filling during the first morning meal, but it did inhibit crop emptying in fasted turkeys by markedly reducing the number of crop contractions. Artificially filling the crop of fasted turkeys prior to the first morning meal did not decrease the amount of feeding activity or the total amount of food consumed during that meal. It is suggested that meal termination is associated with the degree of inhibition of esophageal peristalsis.

Factors affecting meal to pellet intervals in great-horned owls (Bubo virginianus)☆

Abstract 1. 1. Owls fed mice at 0500 had a shorter meal to pellet interval (MPI) than those fed at 1500 regardless of the size of the meal. 2. 2. As meal sizes increased, MPI generally became longer. 3. 3. Greater amounts of proteinaceous (horse meat in mouse skins) or lipid (bovine fat in mouse skins) materials delayed pellet egestion while the absence of these materials or the presence of undigestible material (pellets in mouse skins) appeared to hasten pellet egestion.

Gastric motility in great horned owls (Bubo virginianus).

Abstract 1. 1. The mean amplitude of gastric pressure changes (4·3 mm Hg) was considerably greater than anticipated from previous reports. 2. 2. Three phases in the digestion of a meal were apparent from records of gastric pressure changes. The phases were termed the mechanical digestion phase, chemical digestion phase and pellet formation and egestion phase. Contraction frequency was greatest during the first phase while contraction amplitude was greatest during the third phase. The lengths of the phases varied with the quantity eaten by an owl. 3. 3. The gastroduodenal contraction sequence began in the glandular stomach, then the muscular stomach and lastly the duodenum. In the muscular stomach, contractions began adjacent to the gastric isthmus and proceeded around the circumference of the muscular stomach to the pylorus.

Food metabolizability and water balance in intact and cecectomized great-horned owls

Abstract 1. 1. In great-horned owls food metabolizability, food intake and body weight were not significantly affected by cecectomy. 2. 2. Following cecectomy, water ingestion increased.