Objective—To determine the origin of the nonacid
(nonparietal) component of gastric secretions in horses
induced by pentagastrin infusion.
Procedure—A Latin square design was used, involving
6 horses, 3 treatments, and 2 duodenal intubation
conditions (catheter with balloon to obstruct pylorus
[B] or without balloon allowing movement of contents
between stomach and duodenum [NB]). Each horse
had an indwelling gastric cannula and a catheter positioned
in the duodenum. Gastric and duodenal contents
were collected during 15-minute periods. Each
experiment consisted of serial collection periods:
baseline; infusion of pyrilamine maleate (1 mg/kg of
body weight, IV); not treated; and IV infusion of saline
(0.9% NaCl) solution alone, saline solution containing
pentagastrin (6 µg/kg·h), or saline solution containing
histamine (30 µg/kg·h). Volume of samples was
recorded, and electrolyte concentrations were measured.
Results—Pentagastrin and histamine stimulated
maximal acid output; however, during NB conditions,
pentagastrin-induced concentration of hydrogen
ions was significantly less than during histamine or
pentagastrin infusions during B conditions. The large
volume produced in response to pentagastrin during
NB conditions was accompanied by increased sodium
ion output that was greater than for pentagastrin
during B conditions, but both values were significantly
greater than values for histamine during B or
Conclusions and Clinical Relevance—Nonparietal
secretions collected during IV infusion of pentagastrin
are duodenal in origin. Reflux of duodenal contents
into the stomach of horses is enhanced by pentagastrin.
Flow of duodenal contents into the stomach
could have implications in the pathogenesis of ulcers
in horses. (Am J Vet Res 2000;61:1133–1139)
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 determine the effects of horse age, osteochondral injury, and joint type on a synthesis biomarker and 3 degradative biomarkers of type II collagen in Thoroughbreds.
Animals—Healthy rested adult (3- to 12-year-old) Thoroughbreds (n = 19), yearling (1- to 2-year-old) Thoroughbreds (40), and Thoroughbred racehorses (2 to 7 years old) undergoing arthroscopic surgery for removal of osteochondral fragments that resulted from training or racing (41).
Procedures—Samples of blood and metacarpophalangeal, metatarsophalangeal, or carpal joint synovial fluid (SF) were collected from all horses. Commercially available assays were used to analyze SF and serum concentrations of type II collagen biomarkers of synthesis (carboxy propeptide of type II collagen [CPII]) and degradation (cross-linked C-telopeptide fragments of type II collagen [CTX II], neoepitope generated by collagenase cleavage of type I and II collagen [C1,2C], and neoepitope generated by collagenase cleavage of type II collagen [C2C]).
Results—Osteochondral injury affected concentrations of CPII, CTX II, C1,2C, and C2C in SF, serum, or both, compared with concentrations in healthy adult horses. Compared with adult horses, yearling horses had increased SF or serum concentrations of degradative biomarkers (CTX II, C1,2C, and C2C). Concentrations were higher in carpal than metacarpophalangeal or metatarsophalangeal joints for all biomarkers in osteochondral-injured horses. Variable differences in SF concentrations between joint types were detected in healthy adult and yearling horses.
Conclusions and Clinical Relevance—Horse age, osteochondral injury, and joint type all significantly affected type II collagen biomarker concentrations in SF and serum of Thoroughbreds.
Objective—To characterize intragastric pH profiles in
critically ill foals and determine whether administration
of ranitidine altered pH profiles.
Design—Prospective observational study.
Animals—23 hospitalized neonatal foals ≤ 4 days of
Procedure—Intragastric pH was measured continuously for up to 24 hours by use of an indwelling electrode
and continuous data recording system. In 21
foals, ranitidine was administered IV.
Results—10 foals had predominantly or exclusively
alkaline profiles, 10 had profiles typical of those
reported for healthy foals, with periods of acidity
(hourly mean pH < 5.0 at least once), and 3 had atypical
profiles with periods of acidity. All 10 foals that
had intragastric pH profiles typical of healthy foals survived,
whereas only 2 foals with alkaline profiles survived,
and none of the foals with atypical profiles survived.
The effects of ranitidine administration could
not be assessed in 13 foals because of a high baseline
intragastric pH. In 7 of the remaining 9, ranitidine
administration resulted in an alkalinizing response,
but this response was often of blunted duration.
Ranitidine administration did not appear to alter the
intragastric pH profile in the remaining 2 foals.
Conclusions and Clinical Relevance—Results suggested that hospitalized critically ill foals often have
intragastric pH profiles different from those reported
for healthy foals and may respond differently to ranitidine
administration than do healthy foals. Many critically
ill foals have continuously alkaline intragastric pH
profiles, questioning the need for prophylactic administration
of ranitidine in all critically ill foals. (J Am Vet
Med Assoc 2001;218:907–911)
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 assess the net mechanical load on the distal end of the third metacarpal bone in horses during walking and trotting.
Animals—3 Quarter Horses and 1 Thoroughbred.
Procedures—Surface strains measured on the left third metacarpal bone of the Thorough-bred were used with a subject-specific model to calculate loading (axial compression, bending, and torsion) of the structure during walking and trotting. Forelimb kinematics and ground reaction forces measured in the 3 Quarter Horses were used with a musculoskeletal model of the distal portion of the forelimb to determine loading of the distal end of the third metacarpal bone.
Results—Both methods yielded consistent data regarding mechanical loading of the distal end of the third metacarpal bone. During walking and trotting, the distal end of the third metacarpal bone was loaded primarily in axial compression as a result of the sum of forces exerted on the metacarpal condyles by the proximal phalanx and proximal sesamoid bones.
Conclusions and Clinical Relevance—Results of strain gauge and kinematic analyses indicated that the major structures of the distal portion of the forelimb in horses acted to load the distal end of the third metacarpal bone in axial compression throughout the stance phase of the stride.