Objective—To assess effects of exercise on a treadmill
with changes in gastric volume and pH in the
proximal portion of the stomach of horses.
Animals—3 healthy adult horses.
Procedure—A polyester bag of approximately 1,600
mL was placed into the proximal portion of the stomach
of each horse via a nasogastric tube. Changes in
bag volume, determined by an electronic barostat,
were recorded before, during, and after a training session
on a treadmill with and without prior withholding
of food. In separate experiments, pH in the proximal
portion of the stomach was continuously recorded
during exercise for fed and food-withheld conditions.
Finally, changes in intra-abdominal and intragastric
pressure were simultaneously recorded during a
Results—Bag volume rapidly decreased to nearly
zero during trotting and galloping. Conversely, a return
to walking resulted in a sharp increase in volume and
a return to pre-exercise values. Intragastric and intraabdominal
pressures increased almost in parallel with
walking, trotting, galloping, and galloping on a slope.
Gastric pH decreased rapidly to < 4 at the beginning
of walking, continued to decrease during trotting and
galloping, and remained low until a return to walking.
Conclusions and Clinical Relevance—Increased
intra-abdominal pressure during intense exercise in
horses causes gastric compression, pushing acidic
contents into the proximal, squamous-lined region of
the stomach. Increased duration of acid exposure
directly related to daily duration of exercise may be
the reason that squamous lesions tend to develop or
worsen when horses are in intensive training programs.
(Am J Vet Res 2002;63:1481–1487)
Objective—To measure plasma cholecystokinin (CCK) activity and the effect of a CCK-1 receptor antagonist on accommodation of the proximal portion of the stomach, and subsequent gastric emptying, in horses after ingestion of high-fat or high-carbohydrate meals.
Animals—6 healthy adult horses with gastric cannulas.
Procedures—In the first study, horses were offered a high-fat (8% fat) or a high-carbohydrate (3% fat) pelleted meal of identical volume, caloric density, and protein content. Related plasma CCK-like activity was measured by radioimmunoassay (RIA). In a separate experiment, a horse was fed a grain meal with corn oil and phenylalanine, and plasma CCK activity was assessed by bioassay. A second study evaluated the effect of a CCK-1 receptor antagonist, devazepide (0.1 mg/kg, IV), on gastric accommodation and emptying following a meal of grain supplemented with either corn oil (12.3% fat) or an isocaloric amount of glucose (2.9% fat). Gastric tone was measured by a barostat and emptying by the 13C-octanoic acid breath test.
Results—No plasma CCK-like activity was detected by RIA or bioassay before or after ingestion of meals. Preprandial devazepide did not alter the gastric accommodation response but did significantly shorten the gastric half-emptying time and time to peak breath 13CO2 content with the glucose-enriched meal.
Conclusions and Clinical Relevance—In horses, CCK participates in regulating the gastric motor response to a meal. Compared with other species, horses may be more responsive to carbohydrate than fat. A vagovagal reflex most likely mediates this regulation, with CCK as a paracrine intermediary at the intestinal level.
Objective—To assess gastric tone in the proximal portion
of the stomach in horses during and after ingestion
of 4 diets (2 diets of grain and 2 diets of hay).
Animals—6 adult horses.
Procedure—A polyester bag with a volume of approximately
1,600 ml was inserted through a gastric cannula
into the proximal portion of the stomach of each
horse. Internal pressure of the bag was maintained at
2 mm Hg by use of an electronic barostat, and
changes in bag volume were recorded before, during,
and after horses consumed diets of grain or hay. Each
horse was fed 0.5 and 1.0 g of grain/kg and 0.5 and 1.0
g of hay/kg. Changes in bag volume measured by use
of the barostat were indirectly related to changes in
tone of the gastric wall.
Results—Food intake caused a distinctly significant
biphasic increase in volume. The first phase was during
active ingestion, which was followed shortly by a
second, more prolonged postprandial phase. The
ingestion-related phase of the response to intake of a
diet of 1 g of hay/kg was significantly greater than that
for the other diets.
Conclusion and Clinical Relevance—Ingestion of a
solid meal induces a biphasic relaxation response in
the proximal portion of the stomach of horses.
Magnitude of the ingestion-related phase may be
determined by size of the meal. (Am J Vet Res 2002;
Objective—To determine the effect of pH with or
without pepsin or taurocholic acid on the bioelectric
properties of gastric squamous mucosa in horses.
Sample Population—Gastric tissues obtained from
16 adult horses that did not have evidence of gastric
Procedure—Bioelectric properties of squamous
mucosa were determined, using modified Ussing
chambers. Tissues then were exposed to mucosal
pepsin (1 mg/ml) or taurocholic acid (2.5 mM) under
neutral (pH 7.4) or acidic (pH 1.7) conditions.
Results—Exposure of mucosal sheets to an acidic pH
resulted in an immediate and sustained decrease in
transmembrane potential difference and calculated
tissue resistance. Pepsin or taurocholic acid did not
significantly affect bioelectric variables when added to
a mucosal bath solution of pH 7.4. A synergistic effect
between pepsin or taurocholic acid and mucosal acidification
was not detected.
Conclusions and Clinical Relevance—Mucosal acidification
with or without pepsin or taurocholic acid
resulted in reduced tissue resistance. These data support
the contention that squamous erosions or ulcers
in horses are mediated, in part, by prolonged exposure
of gastric squamous mucosa to luminal acid.
(Am J Vet Res 2002;63:744–749).
Objective—To evaluate the effect of ingestion of a
high-carbohydrate versus a high-fat meal on relaxation
of the proximal portion of the stomach and subsequent
gastric emptying in horses.
Animals—6 healthy adult horses.
Procedure—The study consisted of 2 phases. In
phase I, horses were offered a high-fat (8% fat) or a
high-carbohydrate (3% fat) pelleted meal (0.5 g/kg) of
identical volume, caloric density, and protein content.
In phase II, meals consisted of a commercial sweet
feed meal (0.5 g/kg) or this meal supplemented with
corn oil (12.3% fat) or an isocaloric amount of glucose
(2.9% fat). Proximal gastric tone was measured by
variations in volume of an intragastric bag introduced
through a gastric cannula and maintained with a constant
internal pressure by an electronic barostat. Rate
of gastric emptying was measured simultaneously
with the 13C-octanoic acid breath test. Interaction
between both techniques was studied in additional
Results—Meals with higher carbohydrate content
induced a significantly more prolonged receptive
relaxation of the proximal portion of the stomach than
those with higher fat content, but the accommodation
response was similar. Labeling the meals with
the breath test marker influenced the accommodation
response measured by the barostat. Gastric emptying
rates were not significantly different between
meals, although those high in carbohydrate initially
emptied more slowly.
Conclusions and Clinical Relevance—In horses, in
contrast to most species, dietary fat supplementation
may not have a profound effect on gastric motility.
(Am J Vet Res 2005;66:897–906)
Objective—To evaluate the efficacy of omeprazole
paste, a commonly used antiulcer drug, on intragastric
pH in clinically normal neonatal foals.
Animals—6 clinically normal foals between 5 and 14
days of age.
Procedure—Intragastric pH was recorded in each
foal by use of a disposable antimony pH electrode
with internal reference. Values for intragastric pH
were recorded every 4 seconds by use of an ambulatory
pH monitor. There were two 24-hour recordings
of intragastric pH for each foal, with 24 hours
between recordings. Foals were not administered
any drugs during the first recording. Foals were
administered omeprazole paste (4 mg/kg, PO) 1
hour after the start of the second recording. Mean
pH was calculated for each hour of each 24-hour
recording session. Hourly mean values were compared
between the first and second 24-hour
Results—Complete data were obtained from 4 of 6
foals during the first 24-hour recording and 6 of 6 foals
during the second 24-hour recording. Foals had significantly
higher mean hourly intragastric pH for hours
2 to 22 following omeprazole administration, compared
with corresponding hourly pH values in foals
during the first recording.
Conclusions and Clinical Relevance—Omeprazole
paste can effectively increase intragastric pH in
clinically normal neonatal foals within 2 hours after
oral administration of the first dose and can be
administered to neonatal foals at the rate of
4 mg/kg, PO, every 24 hours. (Am J Vet Res
Objective—To measure concentrations and activities of major digestive enzymes in healthy equine pancreatic tissue.
Animals—7 adult horses with normal pancreatic tissues.
Procedures—Small pieces of pancreatic tissue were collected immediately after euthanasia, immersed in liquid nitrogen, and maintained at −80°C until analyzed. Concentrations and activities of amylase, lipase, chymotrypsin, trypsin, and elastase were determined by use of a microtiter technique. Relative pancreatic protein concentrations were determined by use of bovine serum albumin as the standard. Pancreatic DNA was extracted and con-centrations determined by use of the diphenylamine method with calf thymus DNA as the standard.
Results—The pancreatic cellular concentration of each enzyme, expressed as units per milligram of DNA, was consistent among horses. Cellular concentration of lipase (1,090.8 ± 285.3 U/mg of DNA) was highest, followed by amylase (59.5 ± 9.8 U/mg of DNA). Elastase, trypsin, and chymotrypsin were detected in small concentrations (1.9 ± 0.6, 3.5 ± 1.5, and 9.6 ± 2.9 U/mg of DNA, respectively). Similar results were obtained for specific activities of the enzymes.
Conclusions and Clinical Relevance—Results were unexpected because, under natural conditions, the predominant energy source for horses is carbohydrate. These results may indicate, in part, the reason horses seem to tolerate large amounts of fat added to their diet.
Objective—To evaluate the reliability of a method for
inducing colic via small intestinal distention in horses
and to examine the analgesic potential of bilateral
electroacupuncture (EAP) at the Guan-yuan-shu (similar
to BL-21) acupoint.
Animals—5 healthy adult horses, each with a gastric
Procedure—A polyester balloon connected to an electronic
barostat was introduced into the duodenum via
the gastric cannula. At 2 specified intervals (before and
after commencement of EAP), the balloon was inflated
to a barostat-controlled pressure that induced signs of
moderate colic. Each inflation was maintained for 10
minutes. Heart and respiratory rates were continuously
recorded. Frequency of various clinical signs of colic was
recorded by 2 trained observers during various combinations
of balloon inflation and EAP. Each horse received
each of 5 treatment protocols (EAP at 20 Hz, sham EAP
at 20 Hz, EAP at 80 : 120 Hz dense:disperse, sham EAP
at 80 : 120 Hz dense:disperse, no treatment). Sham EAP
was at a point located 2 cm lateral to the Guan-yuan-shu
Results—Duodenal distention consistently induced a
significant increase in frequency of signs of colic.
None of the EAP protocols caused a significant reduction
in frequency of these clinical signs during distention.
Conclusions and Clinical Relevance—The method
described is reproducible and highly controllable
method for inducing colic that involved duodenal distention
that should be useful in evaluating the efficacy
of various analgesic strategies. Bilateral EAP at the
Guan-yuan-shu acupoint was ineffective in reducing
signs of discomfort induced by this method. (Am J Vet
Objective—To determine factors associated with
development of postoperative ileus (POI) in horses
undergoing surgery for colic.
Design—Prospective case-control study.
Animals—251 horses undergoing colic surgery, of
which 47 developed POI.
Procedure—Signalment, history, clinicopathologic
data, pre- and postoperative treatments, lesions,
complications, costs, and outcome were recorded for
all horses during hospitalization.
Results—Variables associated with increased odds of
POI included small intestinal lesion, high PCV, and
increased duration of anesthesia. There was modest
evidence that pelvic flexure enterotomy and intraoperative
administration of lidocaine may have reduced
the odds of developing POI.
Conclusions and Clinical Relevance—Findings during
the preoperative and intraoperative periods can be used
to identify horses at increased risk of POI. Reducing surgical
and anesthetic duration should decrease the incidence
of POI. ( J Am Vet Med Assoc 2004;225: