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In a multicentre trial, 13 cannulated horses were treated orally once daily with a paste that delivered omeprazole at a dose of 4 and 5 mg/kg bwt in a 2-period crossover design to evaluate steady state gastric acid suppression. In each period, basal (unstimulated) and pentagastrin-stimulated gastric output were evaluated at 5-8 h after 5 doses, at 13-16 h after 10 doses, and at 21-24 h after 15 doses. Baseline data for gastric acid secretion were collected once for each horse in the month prior to initiation of omeprazole treatment. The inhibition of gastric acid secretion relative to baseline values, following treatment with omeprazole, were calculated and expressed as per cent. Pharmacokinetic data were also collected in this trial. At 4 mg/kg bwt, the oral paste formulation of omeprazole inhibited both basal and pentagastrin-stimulated gastric acid secretion by 99% at 5-8 h after treatment and by 83% (basal) and 90% (pentagastrin-stimulated) at 21-24 h. Inhibition following the administration of omeprazole at a dose of 5 mg/kg bwt was not significantly greater than when given at 4 mg/kg bwt. The results from this study could possibly lead to the development of an effective and practical antisecretory treatment of ulcer disease in horses.

The antisecretory activity of omeprazole on gastric acid when administered i.v., intragastrically or per os, was evaluated in 2 female and 3 castrated male horses. Each horse had been prepared with a chronic indwelling gastric cannula. A single i.v. administration of omeprazole (1.5 mg/kg bwt) was effective in abolishing basal and pentagastrin (PG)-stimulated acid secretion. Once daily, nasogastric administration of omeprazole in acid-stable granules for 5 days inhibited acid secretion in a dose-dependent manner: 57% (1.5 mg/kg bwt) and 98% (5.0 mg/kg bwt) reduction of PG-stimulated acid secretion. The degree of inhibition was maintained over a 19 day treatment period with once daily dosing. A prototype oral paste formulation containing either acid-stable omeprazole granules or uncoated omeprazole powder was equipotent when compared to a similar dosage of acid-stable omeprazole granules administered by nasogastric tube. A dose-dependent inhibition was seen with the oral paste formulation containing omeprazole powder: 55% (1.5 mg/kg bwt) and 77% (3.0 mg/kg bwt) reduction of PG-stimulated acid secretion after 5 days. Therefore, a paste formulation of omeprazole powder may offer an effective, easily administered, once daily acid inhibitory treatment for gastric ulcer disease in horses.

This article represents an attempt to provide an overview of the current knowledge of equine gastroduodenal secretory and motor activity, with respect to how these functions are controlled and interact. First, the equine gastric mucosal anatomy is discussed in comparison with other monogastric species, with some attention directed at the large nonglandular portion in relation to its function, or lack thereof. Next, control of gastric acid secretion, as assessed by the collection of gastric contents from a cannula or continuous measurement of their changes in pH, is reviewed, pointing out that there appears to be a relatively unobstructed movement of contents between stomach and duodenum in the horse, which can have a strong influence on pH of the gastric contents in particular. Then, methods of evaluating gastroduodenal motility, including recording of myoelectrical activity and changes in intraluminal pressure, and transit of radiolabelled contents from stomach into duodenum, are discussed. Finally, the apparent influence of the gastroduodenal migrating motility complex (MMC) on the composition of fasting gastric contents is introduced to underscore the observation that reflux of duodenal contents into the stomach is probably a common occurrence in the horse, particularly during periods of MMC-related cessation of antral motility.

Intrauterine pressure was measured in 4 reproductively normal mares and 4 mares with delay in uterine clearance after administration of oxytocin to determine if intrauterine pressure varied between dosage and group. Changes in intrauterine pressure were measured during estrus, when a follicle was > or =35 mm, using a Millar "Mikro-tip" catheter that had 3 discrete pressure sensors/channels. Mares received 4 different treatments of 10, 5, 2.5 or 0 IU (vehicle) of oxytocin. The protocol for each treatment consisted of a 10-min baseline recording, administration of treatment and measurement of changes in intrauterine pressure for 65 min. After administration of the first two treatments, mares were rested for 2 h and the protocol repeated for the remaining 2 treatments. Changes in intrauterine pressure were measured on a physiograph and stored in a computer. The results were analyzed by 4x4 Latin Square Design analysis of variance (ANOVA) using the GLM procedure of the Statistical Analysis System. The ANOVA detected a main effect of treatment (P<0.01) and mare (nested within group; P<0.01) but no effect of channels, group or treatment-by-group interaction. There was a dose-dependent increase in uterine activity in both normal mares and those with delayed uterine clearance. A dose of 10 IU of oxytocin induced a larger number of uterine contractions (5.67+/-0.06) for a longer time (24.09+/-1.18 min) than the 5 IU (4.16+/-0.06 contractions and 16.31+/-1.18; P<0.01 min) or 2.5 IU dose (4.08+/-0.06 contractions and 17.61+/-1.18 min). The first intrauterine wave occurred most often near the tip of the horn in 10 of 12 recordings in normal mares and in 8 of 12 recordings in mares with delayed uterine clearance. It was then propagated from the middle of the horn to the uterine body just cranial to the cervix. There was no pattern of propagation for subsequent intrauterine pressure waves. We conclude that the difference in spontaneous clearance of the uterus between the 2 groups is not reflected in their response to exogenous oxytocin as determined by changes in intrauterine pressure.

An adult female southern black rhinoceros (Diceros bicornis minor) experienced intermittent periods of regurgitation while eating, suggesting an esophageal disorder. Endoscopy for evaluation of the trachea, esophagus, and stomach revealed a 30-mm nasopharyngeal orifice with associated recess located in the caudodorsal pharynx and a 10-cm dilated segment of the distal esophagus that was presumably the cause of regurgitation. Dietary management of esophageal dilation through short-term utilization of a "soft feed" program successfully eliminated the regurgitation. This is the first report of esophageal dysfunction in a rhinoceros.

Objective: To determine gastric secretory responses in horses treated with histamine and to determine the dose of histamine needed to elicit maximal gastric secretion., Animals: 6 adult horses with an indwelling gastric cannula., Procedure: Gastric contents were collected in 15-minute periods, and volume, pH, hydrogen ion concentration, hydrogen ion output, sodium concentration, and sodium output were determined. Values were determined without any treatment (baseline), after administration of pyrilamine maleate (1 mg/kg of body weight, i.v., given during a 15-minute period), and during 1-hour infusions of histamine at 3 rates (7.5, 15, and 30 microg/kg/h, i.v.)., Results: Volume and hydrogen ion concentration of gastric contents and hydrogen ion output were significantly increased, compared with baseline values, during histamine infusion. Mean hydrogen ion concentration and hydrogen ion output were significantly greater during infusion of histamine at a rate of 15 or 30 microg/kg/h than at a rate of 7.5 microg/kg/h. Sodium concentration was significantly decreased, compared with baseline value, during histamine infusion, but sodium output was unchanged., Conclusions: Histamine at doses of 15 and 30 microg/kg/h, i.v. stimulated maximal gastric secretion in horses. Histamine appeared to induce only parietal secretion., Clinical Relevance: This study provides additional information related to equine gastric physiology, which may benefit further understanding of the pathogenesis of peptic ulcer disease.

A yearling Arabian filly was referred to the Veterinary Medical Teaching Hospital with a history of weight loss, profound anemia, and peritoneal effusion. At necropsy, a large, soft, mottled tan and red neoplastic mass was at the pelvic inlet replacing the left ovary. Additional tumor nodules of various sizes were disseminated throughout the mesentery, diaphragm, and serosal surfaces of the abdominal viscera. Histologically, the neoplasm had sheets of large round to polygonal cells separated into lobules by fibrous connective tissue with multifocal areas of necrosis. Tumor cells stained strongly for alkaline phosphatase. Immunohistochemically, tumor cells expressed vimentin and were negative for cytokeratin. Ultrastructurally, the neoplastic cells had a characteristic nucleolus with an elaborate reticular nucleolonema in an irregular configuration. This is the first in-depth detailed report of this very rare germ cell tumor of the ovary in horses.

Objective: To determine intragastric pH in newborn foals and to examine the effect of i.v. or oral administration of an H2-receptor antagonist on intragastric pH., Design: Prospective controlled study., Animals: 6 healthy mixed-breed neonatal foals., Procedure: Intragastric pH was measured, using an antimony electrode. Foals were monitored on days 2, 4, and 6 after birth, and each received 3 treatments. The pH was recorded for 4 hours before treatment and for 10 hours after ranitidine administration (2 mg/kg [0.91 mg/lb] of body weight, i.v.; 6.6 mg/kg [3 mg/lb], PO) or 20 hours after corn syrup administration. Mean and median pH and percentage of time pH was > or = 4 were calculated., Results: Mean intragastric pH significantly increased for 5 hours after i.v. administration of ranitidine, compared with baseline data. Percentage of time intragastric pH was > or = 4 increased significantly for 4 hours after ranitidine administration, and median pH increased significantly for hours 2 to 4 after administration. Oral administration of ranitidine significantly increased mean and median pH for hours 2 to 8 after administration and percentage of time pH was > or = 4 for hours 2 to 7 after administration., Clinical Implications: Neonatal foals have highly acidic gastric fluid. Intravenous or oral administration of ranitidine significantly increased intragastric pH for 4 and 8 hours, respectively. Suckling affected intragastric pH and underscored the need for frequent feeding of neonatal foals.

Objective: To evaluate the effect on equine duodenal motility of some analgesic agents commonly used to treat colic., Animals: 4 healthy adult healthy horses--2 mares and 2 geldings--which were carrying an indwelling gastric cannula made of silastic rubber. One horse also carried 2 long-term indwelling bipolar electrodes that had been sutured onto the duodenum and jejunum., Procedure: To ensure an empty stomach, solid food was withheld from horses for around 20 hours prior to an experiment. Using videoendoscopic guidance, an 8-F catheter with 3 small, discrete pressure sensors was passed through the gastric cannula and directed into the proximal portion of the duodenum. Deflection of the recording pen, to which the catheter was attached, indicated a motile event in that section. Drugs (treatment) were given into the jugular vein in a randomized block design, 1 treatment/experiment, after a 1-hour baseline recording. Treatments were: 2 ml of 0.9% NaCl, xylazine (XYL, 0.5 mg/kg of body weight), detomidine (DET, 0.0125 mg/kg), or a xylazine/butorphanol combination (XYB, 0.5/0.05 mg/kg). Each horse received each treatment twice. All positive pressure peaks > 5 mm of Hg recorded from the most proximal sensor on the catheter were counted in 15-minute blocks. Each mean 15-minute posttreatment value was compared with the baseline value for that specific treatment., Results: There was no significant difference between baseline values. All treatments significantly (P < 0.05) reduced frequency of pressure peaks below their respective pretreatment values, but to variable degrees and durations. Comparatively, XYL had the least effect, with mild, though significant, reduction for only the first 30 posttreatment minutes; DET and XYB caused a significant marked reduction for 1 hour after treatment., Conclusions: The profound suppressive effect of a routine dose of detomidine or xylazine/butorphanol combination on equine duodenal motility must be considered when using these agents for management of colic, especially when encouragement of intestinal motility is desirable.

Objective: To determine the effect of erythromycin lactobionate (ERY) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum., Animals: 6 healthy adult ponies., Procedure: After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were administered directly into the cecal apex. The following drug concentrations were tested: ERY, 0.01, 0.10, 1.0, and 10.0 mg/kg of body weight; ERY, 0.10 mg/kg bolus; and saline (0.9% NaCl) solution, 10 ml. All treatments, with the exception of the 0.10-mg/kg bolus and saline solution, were infusions administered i.v. during a 60-minute period in a randomized complete block design. Each treatment was administered 2 times/pony. Dual-phase scintigraphic images were obtained, and the best-fit function was determined for each study, using data from the right side. Myoelectric data were collected before and after each treatment and analyzed for spike burst rate, relative activity, and burst duration., Results: The time to 50% emptying (t50) after ERY administration was dose dependent, and all treatments, with the exception of the 0.01-mg/kg infusion, resulted in a significantly shorter t50 than that observed after saline administration (230.2 +/- 17.12 minutes). The shortest t50 was observed after the 1.0 mg/kg dosage of ERY (76.9 +/- 22.0 minutes). Although not significantly different, the t50 and beta were shorter (108.6 +/- 25.9 minutes) and steeper after a bolus dose of 0.10 mg/kg of ERY than after infusion at the same dosage (131.1 +/- 18.7 minutes)., Conclusions and Clinical Relevance: ERY may be a useful prokinetic for prevention or treatment of cecal motility dysfunction. The ability of ERY to evoke a similar response during the early postanesthetic or postoperative period remains to be determined.

Objective: To determine effect of xylazine hydrochloride (XYL), yohimbine hydrochloride (YOH), bethanechol chloride (BET), neostigmine methyl sulfate (NEO), or flunixin meglumine (FLU) on ileocecocolic myoelectric activity and passage of radiolabeled markers from the cecum., Animals: 6 healthy adult ponies., Procedure: A cecal cannula was surgically implanted, and 12 were sutured to the ileum, cecum, and right ventral colon. After a 12-hour nonfeeding period, 370 MBq of technetium 99m-labeled sulfur colloid in egg albumen and 37 MBq of indium 111-labeled diethyltriaminepentaacetic acid in 60 ml of water were injected into the cecal apex. All drugs were administered i.v. as a bolus, with the exception of NEO, which was given SC: XYL, 0.5 mg/kg of body weight; YOH, 0.075 mg/kg; BET, 0.025 mg/kg; NEO, 0.025 mg/kg; FLU, 1.1 mg/kg; and saline solution (SAL), 10 ml. Drugs were administered in a randomized complete block design, each treatment was administered twice to each pony, and dual-phase scintigraphic images were obtained. The time to 50% emptying (t50) and the slope of the emptying curve (beta) were derived from the calculated power exponential equation., Results: The t50 after BET (184.8 +/- 16.5 minutes) and NEO (124.7 +/- 16.5 minutes) administration were significantly shorter than values after saline (230.2 +/- 17.1 minutes) administration. The t50 after XYL administration (250.5 +/- 18.6 minutes) was longer, and that after YOH administration (190.1 +/- 16.2 minutes) was shorter, than the t50 after saline administration, but neither difference was significant. The t50 and beta after FLU administration differed from those after saline administration. Myoelectric data appeared to be well correlated with drug-induced alterations in isotope clearance., Conclusions and Clinical Relevance: Cholinergic agonists, BET and NEO, have significant effects on the myoelectric activity of ileum, cecum, and right ventral colon, with the net effect of hastening cecal emptying.

Objectives: To determine normal cecal emptying curves for liquid- and solid-phase radiolabeled markers and to further define myoelectric patterns of the ileum, cecum, and colon in healthy ponies., Animals: 6 adult ponies., Procedure: A cecal cannula and 12 bipolar Ag-AgCl recording electrodes were sutured to the ileum, cecum, and right ventral colon of the ponies. Radioisotopes, indium 111-labeled diethyltriaminepentaacetic acid (111In-DTPA) and technetium 99m (99mTc)-labeled sulfur colloid bound to egg albumen, were introduced through the cannula directly into the cecal body. Movement of these markers from the cecum was monitored by a gamma camera, and power exponential clearance curves were generated. Myoelectric data were collected before and after i.v. administration of isotonic saline (0.9% NaCl) solution, and were analyzed for spike burst (SB) rate, relative activity index, and mean burst duration. Myoelectric complexes were identified from observation of chart recordings or compressed, digitized data., Results: Clearance curves were generated for liquid (111In-DTPA)- and solid (99mTc)-phase markers. Marker types were not different with respect to lag phase, but liquid markers emptied at a slightly faster rate than did solids. Baseline values were calculated after saline solution administration for each of the myoelectric variables investigated. A relation between ileal, cecal, and colonic myoelectric activity was identified. Activity consistent with the previously described colonic migrating myoelectric complex in the pelvic flexure was identified in the right ventral colon., Conclusions and Clinical Relevance: Baseline data on normal cecal emptying was obtained; this technique could be used to evaluate the effect of postulated motility-modifying treatments used in equine practice.

Objective: To investigate the prokinetic effect of bethanechol and erythromycin in the upper gastrointestinal tract of healthy horses by measuring the gastric emptying (GE) rate of a radioactive meal., Animals: 4 healthy adult horses., Procedure: After food was withheld for 12 hours, horses were given 370 MBq of 99mTc-labeled sulfur colloid incorporated into egg albumen and 37 MBq of 111In-labeled diethyltriaminepentaacetic acid in 120 ml of water via nasogastric intubation. Intravenously administered treatments were 0.9% NaCl solution, erythromycin (0.1 or 1.0 mg/kg of body weight), or bethanechol (0.25 mg/kg). All drugs were given in 10 ml of 0.9% NaCl solution. Dual-phase scintigraphic images were obtained by use of a gamma camera. The best-fit function was determined for each study, and the resultant curves were then analyzed by use of least squares nonlinear regression. Two variables, time to 50% emptying of the stomach (T-50) and slope of the emptying curve, were derived from the calculated power exponential equation., Conclusions: Treatment had a significant (P < 0.05) overall effect on T-50 of solid-phase GE. The T-50 of bethanechol (30.09 +/- 10.01 minutes), erythromycin at 0.1 mg/kg (59.08 +/- 10.01 minutes), and erythromycin at 1 mg/kg (60.50 +/- 10.01 minutes) were significantly shorter than T-50 after saline administration (89.97 +/- 10.01 minutes). There was a trend (P = 0.09) for the slope of solid-phase GE of bethanechol and erythromycin (0.1 mg/ kg; P = 0.37) to be steeper than that of saline solution. For liquid-phase GE, the T-50 and the slope of bethanechol differed significantly (P < or = 0.05) from those for saline solution., Clinical Relevance: Bethanechol and erythromycin significantly increased solid-phase GE in healthy horses and may have value for use as prokinetic agents in certain gastrointestinal tract diseases.

Objective: To better characterize the source of the large nonparietal secretory response to pentagastrin (PG) expressed in gastric contents of cannulated horses., Animals: Adult cross-bred horses: 4 geldings and 1 mare., Procedure: Horses were prepared by surgical insertion of a silastic gastric cannula from which gastric contents after feed was withheld could be continuously collected by gravity drainage. During experiments, the horses were lightly restrained in stocks, the gastric cannula was opened, and a catheter was inserted into a jugular vein. Over the next 5 hours, gastric contents were collected in 15-minute aliquots for which volume, pH, [Na+], and [K+] were measured. During the first hour, treatment was not administered. At the start of the second hour, either 0.5 mg of omeprazole (OME; dissolved in glycerol formal)/kg of body weight, or 0.9% NaCl (PSS) of comparable volume, was given IV at random as a bolus. At the start of the third hour, IV infusion of PG (6 micrograms/ kg/h) was started and continued for the next 2 hours., Results: The response to PG in the PSS-treated horses was similar to that previously seen-significant decrease in pH and increase in volume of gastric contents, and no change in [K+] and [Na+], but a modest volume-related increase in their respective outputs. After OME treatment, pH of the contents increased sharply and remained between 5 and 6 throughout PG infusion. Sodium concentration significantly increased after OME and virtually paralleled the pH response throughout the rest of the experiment; volume of gastric contents significantly increased in response to PG infusion and resulted in a significant increase in Na output. There was no change in K output in OME-treated animals., Conclusions: PG induces a marked, nonparietal, secretory response into the gastric contents of cannulated horses. The volume and [Na+] of this response was maintained after pretreatment with OME, although the pH of the contents became basic, indicating that this nonparietal response is not mediated by an OME-sensitive proton pump.

Objective: To assess the effect of aluminum hydroxide/magnesium hydroxide antacid and bismuth subsalicylate on gastric pH in clinically normal horses and to develop guidelines on the use of these agents for treatment of peptic ulcer disease in horses., Design: Prospective, randomized, controlled trial., Animals: 5 clinically normal adult horses with chronically implanted gastric cannulas., Procedure: Each horse received all 5 treatments (30 g of aluminum hydroxide/15 g of magnesium hydroxide, 12 g of aluminum hydroxide/6 g of magnesium hydroxide, 10.5 g of bismuth subsalicylate, 26.25 g of bismuth subsalicylate, and 5% methylcellulose control) with only 1 experiment performed each day. Gastric pH was measured via a glass electrode inserted through the gastric cannula for 1 hour before treatment and continued for 2 hours after treatment. Food or water was not given to the horses during the experiment. Measurements of gastric pH obtained during posttreatment hours were compared with pretreatment gastric pH values., Results: Only a dose of 30 g of aluminum hydroxide/ 15 g of magnesium hydroxide resulted in a significant increase in gastric pH over baseline or control values. Mean pH was 5.2 +/- 0.62 and 4.59 +/- 0.48 for posttreatment hours 1 and 2, respectively., Clinical Implications: Oral administration of 30 g of aluminum hydroxide/15 g of magnesium hydroxide to adult horses should result in a mean hourly gastric pH > or = 4.0 for at least 2 hours.

Cecal filtrates from rabbits with cecal ligation-induced mucoid enteropathy have been reported to cause goblet cell hyperplasia in intestinal explants. This study was performed to see whether such filtrates would stimulate mucus secretion from intestinal explants. Filtrates were prepared from cecal contents of five control rabbits, five rabbits that had undergone cecal ligation, and five rabbits that had had the distal branch of the ileocecocolic vessels and nerve incorporated into the cecal ligature. After incubation of each with ileal and colonic explants from five healthy rabbits, the amount of mucus in the media/filtrate solution was measured with an enzyme-linked lectin assay. Significantly (P < 0.05) more mucus was secreted by colonic explants in the presence of cecal filtrates from either of the cecal ligation groups compared with controls. With pooled filtrates from each group, these results were confirmed by measuring secretion of radiolabeled mucus from explants that had been preincubated with [3H]glucosamine. The secretagogue activity was found to be precipitable by 85% ammonium sulfate and destroyed by heat treatment (100 degrees C for 30 min) or acid treatment (pH 1.0 for 30 min). Very little, if any, secretagogue activity was present in cecal vein serum. The results support the hypothesis that the cecal contents of rabbits with cecal ligation-induced mucoid enteropathy stimulate mucus secretion from colonic explants taken from healthy rabbits.

Mucoid enteropathy is a serious disease of rabbits, the cause of which is unknown. Ligation of the cecum has been reported to cause a mucoid enteropathy-like syndrome in 70% of conventional rabbits. The goal of this study was to evaluate this model of mucoid enteropathy in Pasteurella-free, coccidia-free rabbits for use in future studies. Five rabbits served as unoperated controls (group 1). Eight rabbits underwent ligation of the cecum, with large vessels and nerves spared (group 2). In six rabbits the distal branch of the ileocecocolic vessels and nerve were incorporated into the cecal ligature (group 3). At necropsy 3 to 5 days after surgery, all group-3 rabbits had copious amounts of clear, gelatinous mucus in the colon. Only one group-2 rabbit had grossly evident mucus hypersecretion, whereas none of the group-1 rabbits did. Group-3 rabbits had areas of necrosis in the cecum; this was not seen in group-1 or group-2 rabbits. Rabbits of groups 2 and 3 had inflammation of the distal portion of the colon. In specific-pathogen-free rabbits cecal ligation alone did not reliably stimulate mucus hypersecretion but induced a disease similar to natural mucoid enteropathy. Cecal ligation including vessels provided a reproducible syndrome of mucus hypersecretion; however, the severe cecal necrosis was not consistent with the naturally acquired disease.

The pelvic flexure is the midpoint of the equine large colon that marks the junction of dorsal and ventral components. Previous studies of intraluminal pressure in this region indicate that it could be an important motility control center. The present study was undertaken to expand our knowledge of normal myoelectric activity around the pelvic flexure region. Eight bipolar silver wire electrodes were surgically fixed at 5-cm intervals to the colonic serosa of five adult horses, starting 30 cm oral to the pelvic flexure on the left ventral colon and ending 15 cm aboral to the pelvic flexure on the left dorsal colon (LDC). Recordings of myoelectric activity were done after feed had been withheld for 20 h or when the horses had been allowed to eat hay up to the time of the recording session. The activity was recorded on a polygraph, digitized, processed through a commercial graphics software package, and stored on magnetic tape for later analysis. Action potential activity was basically separated into long spike bursts (LSB) that were > or = 4 s duration and short spike bursts (SSB) that were < 4 s duration and quantified by a software program developed exclusively for the equine large intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a change from a diet composed primarily of forage to a diet composed primarily of concentrate on abomasal antral and duodenal motility were assessed in 5 lactating Holstein cows. Antroduodenal motility was measured by use of 8 silver electrodes sutured to the abomasum and duodenum, and abomasal emptying was assessed by continuous measurement of intraduodenal pH. Both diets were fed to achieve a daily dry matter intake of 2.7 kg/100 kg of body weight. The abrupt change in diet did not alter antroduodenal myoelectric activity or abomasal emptying. Initiation of phase III of the migrating myoelectric complex in the proximal portion of the duodenum corresponded with a decrease in abomasal antral spiking activity and an increase in intraduodenal pH. Results suggest that a high concentrate diet alone does not adversely affect antroduodenal motility in adult dairy cattle.

Serum and plasma from horses injected with endotoxin was examined for cytotoxic activity. Each of the cell lines, L929 and WEHI 164 clone 13, was sensitive to the cytotoxic effects of equine serum; however, a precipitation artifact caused by the use of isopropanol in the WEHI assay limited the use of this assay to samples containing less than 2 mg of protein/ml. In foals treated with a sublethal IV bolus of 5 micrograms of lipopolysaccharide (LPS)/kg and in adult horses given a low-dose continuous infusion of LPS (30 ng/kg/h for 4 hours), cytotoxic activity was detected in all serum or plasma samples taken between 30 minutes and 4 hours after LPS infusion began. In horses given either continuous or bolus LPS infusions, circulating cytotoxic activity peaked at 1 to 2 hours before decreasing sharply. The onset of pyrexia after LPS infusion coincided with the appearance of circulating cytotoxic activity, but the temperature remained high, even after cytotoxic activity disappeared. Treatment of horses with flunixin meglumine (1 mg/kg) appeared to blunt the pyrexic effect of low-dose continuous LPS infusion, but had no significant effect on circulating cytotoxic activity. Incubation of serum samples with an antibody raised against a portion of human tumor necrosis factor (TNF) resulted in the removal of greater than 90% of serum cytotoxicity, suggesting strongly that the cytotoxic activity was attributable to TNF. These findings are consistent with the hypothesis that TNF is an early acting mediator of the effects of endotoxin in the horse.

Equine gastric secretion was studied using a gastric cannula model after fasting (basal) and pentagastrin infusion. Gastric secretory rate, pH, osmolality, and electrolyte concentrations and outputs were determined over a 5-h period. Dose-response tests estimated that the maximally effective intravenous dose of pentagastrin was between 3 and 6 micrograms.kg-1.h-1. Basal secretory rate was 278 +/- 29 (SE) ml/15 min, and the pH was 2.00 +/- 0.31. Pentagastrin infusion at 6 micrograms.kg-1.h-1 increased secretory rate to 533 +/- 60 ml/15 min and decreased pH to 1.41 +/- 0.11. Basal gastric acid concentration and output were 38 +/- 5 meq/l and 211 +/- 36 mu eg.kg-1.h-1, respectively. Pentagastrin increased acid concentration to 60 +/- 5 meq/l and acid output to 474 +/- 61 mu eq.kg-1.h-1. Gastric fluid osmolality remained hypotonic during both basal and pentagastrin conditions. Sodium concentration remained high in comparison with hydrogen ion concentration, and sodium output increased during pentagastrin infusion. Equine gastric secretion did not attain maximal acid concentrations nor the marked drop in pH, which has been reported for other monogastric species. These data suggest that in the horse a large nonparietal component exists that modifies parietal secretions and is increased by pentagastrin stimulation.

The function of pteroylpolyglutamate hydrolase (PPH) of pancreatic secretion in the hydrolysis of dietary polyglutamyl folates (PteGlun) in humans is unclear. In this study, PPH was detected in pancreatic juice collected from pigs during both fasting and postprandial conditions. The secretion of PPH was markedly increased following feeding. Pancreatic PPH showed the following characteristics: 1) endo/random hydrolysis of gamma-glutamyl peptide bonds of Pte-Glun substrates, yielding folic acid as the terminal product; 2) maximum activity at pH 4.0-4.5 and maximum stability at pH 7.0; 3) stimulation of activity by Zn2+ and 2-mercaptoethanol; 4) Km values for pteroyltriglutamate (PteGlu3) of 28.7 microM at pH 4.0 and 9.1 microM at pH 5.0; 5) apparent molecular weight of 29,000; and 6) isoelectric point within the range of 8.5-9.0. On the basis of PPH activity, volume of the postprandial secretion and pH profile of enzyme activity, it is suggested that pancreatic PPH may act in vivo in folate digestion and absorption to initiate the deconjugation of dietary PteGlun prior to the action of jejunal brush border PPH.

To investigate the possibility that a disorder of potassium balance may have a role in the development of equine rhabdomyolysis, the potassium concentration within erythrocytes (RBC [K+]) and plasma (P [K+]) was measured in 3 groups of horses: group 1, eight 2-year-old fillies that had postexercise muscle soreness within 48 hours of sample collection; group 2, ten 2-year-old fillies subjected to identical management and training conditions (as fillies of group 1) and that did not have signs of myopathy; and group 3, 32 yearlings of both sexes on the farm of origin of groups 1 and 2 that were pastured and not in training. Creatine kinase activity in serum from horses of groups 1 and 2 was also measured. The mean P [K+] was not significantly different between groups, whereas the mean RBC [K+] was significantly (P less than 0.01) lower in group-1 fillies vs group-2 fillies and group-3 horses. Group-1 fillies also had markedly high serum creatine kinase activity. Results of the study revealed significantly lower RBC [K+] in horses that had had signs of myopathy within the preceding 48 hours. This does not prove a causal relationship between RBC potassium depletion and myopathy, but does suggest that decreased RBC [K+] may be observed in horses with exercise-related myopathy.

Isosmolar oral rehydrating solutions (ORS) used to treat diarrheic calves are low in energy. In contrast, hyperosmolar ORS may have a dehydrating effect. This study was designed to compare the net water and glucose absorption from the small intestine of normal calves given isosmolar or hyperosmolar ORS. Six calves were used for the experiment. A reentrant ileal cannula was implanted surgically. Each calf was fed with either the isosmolar or the hyperosmolar solution. The next day, the second solution was given. Both contained chromium EDTA as a nonabsorbable marker. Changes in the hematocrit, total plasma protein, plasma osmolality, plasma glucose concentration, and ileal volume, osmolality, glucose content, and chromium concentration were monitored for 10 hours. The only statistically significant difference was in the post-feeding plasma glucose level: it peaked at the higher level (p less than 0.05) in calves fed the hyperosmolar solution. In normal calves, the hyperosmolar ORS had no effect on the hydration or on the small intestinal fluid composition.

Four silver-silver chloride electrodes were surgically implanted at 5-cm intervals on the jejunal serosa of 7 neonatal pigs. Daily recordings, 7 h in duration, were made from each piglet beginning 3 days after surgery. Characteristic migrating motility complexes and short, distinct (2.5-5.0 s), rapidly aboral migrating bursts of intense spike activity ("migrating action potential complexes") were seen in all preinfection recordings. Piglets were inoculated with a 1-ml oral dose of a 0.1% gut suspension from coronavirus (transmissible gastroenteritis) infected pigs. This resulted in inappetence, vomiting, and diarrhea, most marked on the second day postinfection, but which had abated by the third day. When compared to recordings from both fed and fasted noninfected (control) animals, infection significantly altered jejunal myoelectrical activity by (a) shortening the duration of the migrating motility complex on day 1 postinfection and prolonging it on day 2, (b) increasing the number of abnormal activity fronts, and (c) decreasing the number of migrating action potential complexes. Slow wave frequency and the duration of phase 3 of the migrating motility complex were unaffected. When compared to fed control animals, infected piglets also showed a slight shortening of phase 1 of the migrating motility complex on day 1 postinfection and a prolongation on days 2 and 3, as well as a shortening of phase 2 on the second and third days postinfection. Changes in myoelectrical activity were not solely due to decreases in food intake, as abnormalities persisted when food intake returned to normal on postinfection day 3, and disruption of the activity front and migrating motility complex duration were purely transmissible-gastroenteritis-virus-induced phenomena. These findings suggest that infection with transmissible gastroenteritis virus disrupts organized propulsive activity in the jejunum of the neonatal pig.

A 4-year-old stallion was examined because of a 2-month history of inappetance and weight loss. Diarrhoea had also developed a month before presentation. Abnormal clinical findings were emaciation, diarrhoea, ventral oedema, palpable mesenteric lymph node enlargement and a large mass in the left cranial portion of the abdomen. Significant laboratory findings were anaemia (packed cell volume 0.21 litres/litre), hypoalbuminaemia (16 g/litre) and xylose malabsorption. The horse was euthanased and at necropsy a 10.5 kg pendunculated mass composed of granulation tissue was found within and attached to the stomach. There was villous atrophy diffusely throughout the small intestine. The inciting cause of the gastric mass was not determined.

The relations between dietary fiber intake and myoelectric activity of the proximal canine colon were examined in four normal beagles fed four diets of varying fiber content in a randomized block design. The basal diet was a canned, meat-based product to which 3, 6, and 9% by weight of alpha-cellulose was added. Colonic motility was monitored using four bipolar Ag-AgCl electrodes. Two slow-wave frequencies were observed: 1) 18.4 +/- 0.1 cycles/min (cpm) and 2) 5.6 +/- 0.03 cpm. Fiber had no effect on either frequency. Spike activity showed three distinct patterns: 1) short bursts phase locked to slow waves of the 18.4 cpm frequency, 2) short bursts phase locked to slow waves of the 5.6 cpm frequency, and 3) prolonged sequences unrelated to slow waves, lasting from 5 to greater than 60 s and grouped in distinct aborally conducted bursts that occurred at a frequency of 2.9 +/- 0.1/h (SE). Fiber had no effect on the frequency of these bursts, but as fiber intake increased there was a linear decrease in burst duration from 11.4 +/- 0.6 min for the basal diet to 8.2 +/- 0.4 min for the high-fiber diet (P less than 0.001). We conclude that luminal factors influence spike burst activity in the proximal colon, because increments of undigestible fiber reduce burst duration on a dose-related basis.

The concentrations of acetate (C2), propionate (C3), isobutyrate (iC4), butyrate (nC4), isovalerate (iC5), and valerate (nC5) were measured in the feces of 16 clinically normal horses and 44 horses with chronic diarrhea of at least 1-month's duration. The diarrheal horses were categorized diagnostically as: (1) no discernible clinical abnormalities other than diarrhea and in some cases, weight loss (open); (2) clinical evidence of strongyle larval migrans; and (3) Salmonella organisms recovered from the feces. Osmolarity of the feces of 14 of the normal and 15 of the sick horses also was measured. The mean concentration of C2 was significantly less (P < 0.05) in feces from horses of all diagnostic categories, whereas there was a significantly increased isobutyrate concentration (P < 0.01) in feces from horses in the open category. When individual volatile fatty acids (VFA) were expressed as percentage of total, only isobutyrate in feces from horses in the open category was significantly different (P < 0.01) from normal and was increased. Some horses were monitored sequentially for a number of weeks. Fecal VFA concentrations showed considerable variability, and a transient decrease of isobutyrate concentration was not necessarily coincidental with cessation of diarrhea. Horses responding to empirical therapy had a more stable reestablishment of a normal fecal VFA distribution. Correlation between total fecal VFA concentration and osmolarity was significant (P < 0.05) for diarrheal horses, but was not significant for normal horses.

Antroduodenal myoelectrical activity and duodenal digesta flow rate in young cattle were assessed by implanted nichrome wire electrodes and reentrant duodenal cannulation with interposed flow-meter. In addition, a small glass electrode was inserted through a duodenal cannula to continuously measure the pH of duodenal contents. When eating only hay ad libitum, the duodenal myoelectrical activity showed the usual migrating myoelectrical complex (MMC) pattern. Duodenal contents pH rose sharply at the end of a period of repetitive spike activity (RSA), or phase III, from pH less than 2 to greater than 5 and remained high through most of the subsequent period of no spike activity (NSA), or phase I, during which there was no antral spiking and no flow of duodenal contents. Feeding milk (pH 6.5) caused a marked increase in antroduodenal spike activity and intraduodenal flow rate, with a concomitant rapid rise in duodenal contents pH from 1.8 +/- 0.3 (SEM) to 5.0 +/- 0.2 which then slowly declined over the next few hours. Within 5 min after the administration of the alpha 2-adrenergic agonist xylazine (25 and 50 micrograms/kg intramuscular), there was a significant increase (P less than 0.05) in antroduodenal spike frequency and a concomitant marked drop in intraduodenal flow rate with a sustained low pH of intraduodenal contents. The results suggest that: (1) continuous measurement of proximal duodenal pH adds a useful dimension to documenting relationships between antroduodenal myoelectrical activity and duodenal digesta flow rate; and (2) increased spike activity in the antroduodenal region does not necessarily indicate an increased duodenal flow rate is occurring.

Feces from 13 healthy horses and 8 horses with chronic diarrhea were subjected to an in vetro fermentation procedure that had been developed for rumen fluid. Fermentations were conducted over 6 hours in a closed system, with and without an essential amino acid (EAA) mixture being added to the basic starch-buffer medium. The addition of EAA caused no significant difference in results of fermentation of feces from healthy horses. For diarrheic animals, there was a significant (P less than 0.01) increase in gas and total volatile fatty acids production whether EAA were present or not, and alpha-amino nitrogen was utilized in significantly (P less than 0.01) greater amounts only if EAA was present. Fermentations were repeated on feces from five of the eight diarrheal horses after they had been treated with oral iodochlorhydroxyquin for 1 week, and had shown desirable clinical response. A significant difference was not shown between pre- and posttreatment fermentations, except for decreased butyrate production. The results are consistent with the hypothesis that chronic equine diarrhea is primarily a colonic disease and indicates that colonic maldigestion may, in part, be responsible for excess fecal water.

The effect of vagal stimulation induced by 2-deoxy-D-glucose (2DG) on gastric acid and pancreatic bicarbonate output, and portal gastrin and secretin concentrations, was assessed in conscious miniature pigs. Electrical vagal stimulation has previously been shown to induce profuse pancreatic water and bicarbonate secretion in anaesthetized pigs. Pigs in this study were surgically prepared with gastric and pancreatic fistulas and indwelling jugular and portal catheters. An intravenous bolus of 2DG (100 mg/kg body weight) caused a significant increase in both gastric acid and pancreatic bicarbonate output although the latter was about 50% of the reported response to electrical vagal stimulation. Portal gastrin concentration rose significantly after 2DG, but the portal secretin concentration did not change. The presence of secretin in the small intestine was confirmed by intrajejunal HCl infusion. Failure of portal secretin concentration to rise after 2DG infusion rules against a role for this hormone in the pancreatic response.

Seven healthy foals (five ponies and two horses) were maintained on grass pasture with their dams. All foals had normal faeces at the time of testing. An oral xylose absorption test was performed on each foal at one, two and three months of age. Following an 8 h fast, 0.5 g/kg D-xylose as a 10 per cent solution was given via a nasogastric tube. Control and 30 min interval plasma samples were collected for 3 h and the plasma was analysed for xylose using the phloroglucinol microassay technique. Maximum xylose concentration levels were reached between 30 and 60 mins for each of the foals. The mean (+/- sem) peak xylose concentration at one, two and three months of age was 3.14 +/- 0.29, 2.19 +/- 0.30 and 1.25 +/- 0.22 mmol/litre respectively, which were all significantly different from each other. Xylose absorption capacity decreased, therefore, with age, becoming similar to the adult horse by three months of age. The oral xylose absorption test can be used to evaluate small intestinal absorptive capacity in the foal provided that the results are compared with foals of the same age group.

Electromyographic activity and emptying of the abomasum were studied in 3 sheep. Pacesetter potentials (PP), with a frequency of 6.06 +/- 0.05 (X +/- SEM) cycles/minute and propagated distally with an increased conduction velocity approaching the pylorus, were recorded from the distal 11 cm of the antrum. Spike burst and fused action potentials (AP) were superimposed on a variable percentage of PP. The aborad propagation of both types of AP was associated with abomasal emptying at the net rate of 12.61 +/- 1.38 (X +/- SEM) ml/minute. Intraabomasal infusion of 50 ml of a 300 mM solution of either acetic, propionic, or butyric acid was associated with a marked decrease in abomasal AP activity and in the emptying rate. Butyric acid was most effective, followed by propionic and acetic acids. The importance of the results in relation to the pathogenesis of left displaced abomasum (LDA) in dairy cows was noted.

The D-xylose absorption test was applied to clinically normal horses and to horses with signs of gastrointestinal disease. A dosage of 0.5 grams of xylose per kilogram of bodyweight was useful in detecting horses that absorbed the pentose abnormally. The clinical findings were correlated with gross and microscopic findings by biopsy and at necropsy. Gastrointestinal lesions associated with abnormal xylose absorption were classified as: 1) villous atrophy; 2) edema of the lamina propria or 3) necrosis of the lamina propria.

Granulomatous enteritis was diagnosed in 9 horses between 1 and 11 years of age. The complaint in all cases was persistent weight loss. Four of the horses had chronic diarrhea. Two consistent diagnostic features were hypoalbuminemia and decreased phagocytic activity of mesothelial cells in the peritoneal fluid. In 2 cases the diagnosis was confirmed by biopsy of the rectal mucosa. Remaining cases were definitively diagnosed by exploratory laparotomy and biopsy or at necropsy.

Gastric cannulas were placed surgically in 5 young male horses. After a 2-week recovery period, horses were studied once a week. Horses were fasted for 24 hours, and gastric fluid output was collected for 5 continuous hours. Volumes were recorded every 15 minutes, and pH and hydrogen ion concentration were determined in an aliquot from each period. In 10 basal experiments, using 5 horses, volume, pH, and hydrogen ion concentration were continuously variable. Mean acid output was 45.1 +/- 2.02 microEq/15 min/kg (mean +/- SEM). In 6 experiments, using 3 horses, 0.5 mg of ranitidine/kg of body weight, given as an IV bolus after a 1-hour basal collection, significantly (P less than 0.02) inhibited hourly total acid output for 4 hours, but did not significantly change pH. The cannulation technique was done without complications, and horses tolerated the cannula for several months. Seemingly, the horse has a continuously variable gastric acid secretion, and histamine type-2 receptors have a role in this process.

Five clinically normal, mature horses and 11 with chronic diarrhea were given 51Cr-tagged Cohn fraction V equine albumin intravenously. All urine and feces were collected separately, and blood for plasma analysis was taken periodically for 5 to 8 days after injection of the isotope. Plasma clearance of albumin into the intestinal tract of normal horses was calculated as 0.67 +/- 0.23 (SD) ml/kg of body weight/day, with 1.33 +/- 0.69% of the 51Cr dose appearing in the feces in 5 days. Of the 11 diarrheal horses, 8 had a plasma clearance of 0.49 +/- 0.21 ml/kg/day with 1.12 +/- 0.68% of the dose of 51Cr in a 5-day fecal collection, suggesting that excessive losses of plasma protein into the bowel was not a component of their intestinal disease. The 3 other diarrheal horses had a marked protein-losing enteropathy; 1 of these horses had granulomatous enteritis due to Mycobacterium avium infection; another had severe intercellular edema of small and large intestinal mucosa, cause unknown; and intestinal biopsies were not obtained from the 3rd horse. The results suggest that: (1) as with other species that have been studied, daily loss of plasma protein into the bowel of horses is small; (2) most horses with chronic diarrhea do not have protein-losing enteropathy.

The clinical, bacteriologic and pathologic findings of three adult horses suffering from avian tuberculosis are presented. Chronic weight loss and hypoproteinemia were pertinent clinical abnormalities in all three horses. Gross pathologic lesions were characterized by chronic enterocolitis with mesenteric lymphadenopathy in two horses and hepatic granulomas in the third horse. The microscopic diagnoses were chronic, non-caseating granulomatous enterocolitis, and necrotizing, non-mineralizing granulomatous hepatitis, respectively. All three horses had granulomatous lymphadenitis of mesenteric lymph nodes with varying degrees of non-mineralizing, coagulation necrosis. Various serotypes of the Mycobacterium avium-intracellulare complex were isolated from selected tissues and feces.

In 4 healthy horses and 1 Welsh pony, fractional renal excretions of phosphorus (FEp) determined from 9 hourly time collections taken over a 24-hour period were compared to assess whether a single-sample collection would be an accurate indicator of the daily FEp. The mean FEp for each animal varied from 0.115% to 0.302%; the 2 animals with the highest values were significantly different (P less than 0.05) from the 3 with the lowest values. Individual variation within animals was not great, however, because it was calculated that the 24-hour FEp value could be found within +/- 0.087% of the single sample value 95% of the time in a given animal.

Pertinent questions regarding the history of a horse with diarrhoea are listed, as are diagnostic procedures that might be included in a complete clinical work-up. For purposes of discussion, diarrhoea is regarded as "acute" or "chronic" wherein the former concerns cases where the features of the disease are severe with progressive electrolyte imbalance, dehydration, toxaemia, or other life-threatening manifestations and the latter refers to cases that have been prolonged for a month or more. Patterns of disease, including results of diagnostic techniques, are stressed. In the "acute" category, salmonellosis, haemorrhagic and oedematous colon (Colitis X), acute peritonitis, and Corynebacterium equi infection are discussed in some detail. In the "chronic" group, strongyle larval migrans, granulomatous enteritis, chronic liver disease, Corynebacterium equi infection and chronic salmonellosis are emphasized.

Gastroenterostomy was performed in 14 foals to treat gastric outflow obstruction caused by advanced gastroduodenal ulcer disease. The onset of excessive salivation and teeth grinding, without response to medical treatment, combined with endoscopic and radiographic evidence of gastric outflow obstruction, were indications for surgical intervention. Successful outcome in 5 foals was attributed to early diagnosis, patient stabilization, early surgical correction, and postoperative management including antibiotics and antiulcer medication.

The purpose of this study was to define and quantify patterns of normal jejunal myoelectrical activity in the conscious neonatal pig. Twelve 3-day-old piglets were obtained from a local herd. At 7 days of age four bipolar Ag-AgCl electrodes were surgically implanted at 5 cm intervals on the jejunum. Piglets were divided into fed (n = 7) and fasted (n = 5) groups and a minimum of four daily recordings were made from each pig between 7 and 14 days of age. Slow wave and spike activity were seen in all animals. Slow waves occurred at a frequency of 17.0 +/- 0.3 cycles/min (c.p.m.) in fed and 16.8 +/- 0.2 c.p.m. in fasted piglets. Spike activity predominated, occurring in characteristic migrating myoelectrical complexes (m.m.c.s.) and occupying 79% of the recording time in fed and 73% in fasted piglets (P less than 0.05). The activity front (phase 3) of the m.m.c. recurred every 47.7 +/- 2.4 min in fed, and 50.9 +/- 2.3 min in fasted piglets. The m.m.c. periodicity in both groups was irregular, with a range of 4-145 min in fed, and 8-104 min in fasted piglets. Activity fronts lasted 4.8 +/- 0.1 min in fed and 4.4 +/- 0.1 min in fasted piglets. All piglets demonstrated intense, short (2.5-5.0 s), distinct bursts of intense spike activity (migrating action potential complexes, m.a.p.c.s.). These were rapidly conducted in an aboral direction at a velocity of 1.8 cm/s in fed, and 0.8 cm/s in fasted piglets (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)