Objective—To evaluate the effect of an indwelling
nasogastric tube on gastric emptying of liquids in
Animals—9 healthy adult horses.
Procedure—A randomized block crossover design
was used. For treatment group horses, a nasogastric
tube was placed and 18 hours later, acetaminophen
was administered; the nasogastric tube remained in
place until the experiment was complete. For control
group horses, a nasogastric tube was passed into the
stomach, acetaminophen was administered, and the
nasogastric tube was removed immediately. Serial
blood samples were collected 15 minutes before and
after administration of acetaminophen. Serum concentration
of acetaminophen was determined by use
of fluorescence polarization immunoassay. The variables,
time to maximum acetaminophen concentration
(Tmax) and the appearance constant for acetaminophen
(Kapp), were determined. The values for
Kapp and Tmax in horses with and without prolonged
nasogastric tube placement were compared.
Results—No significant difference was found in Kapp
between horses with and without prolonged nasogastric
tube placement; the median difference in Kapp
was 0.01 min–1 (range, –0.48 to 0.80 min–1). No significant
difference was found in Tmax between horses
with and without prolonged nasogastric tube placement;
the median difference in Tmax was 5 minutes
(range, –30 to 50 minutes). Reanalysis of data following
the removal of possible outlier values from 1
horse resulted in a significant difference in Tmax
between horses with and without prolonged nasogastric
Conclusions and Clinical Relevance—Although no
clinically important impact of 18 hours of nasogastric
intubation was found on gastric emptying in healthy
horses, considerable variability in Kapp and Tmax was
found among horses. (Am J Vet Res 2005;66:642–645)
Objective—To assess signalment, history, results of
clinical and laboratory testing, and outcome for beef
cattle with a left displaced abomasum (LDA), right displaced
abomasum (RDA), or abomasal volvulus (AV).
Animals—19 beef cattle with an AV, LDA, or RDA.
Procedure—Signalment; history; results of physical
examination, diagnostic testing, and surgical exploration;
and condition of the animal at discharge were
obtained from medical records.
Results—Fourteen cattle had an AV, 4 had an RDA,
and 1 had an LDA. Duration of clinical signs ranged
from 1 to 21 days. Eighteen cattle had an AV or RDA;
7 were Brahmans, 12 were males, and median age
was 10 months. Abdominal distention was observed
in 11 cattle, heart rate of ≥ 100 beats/minute was
detected in 14, and the abomasum was palpable per
rectum in all cattle in which per rectal examination
was performed. Leukocytosis, neutrophilia, hyperglycemia,
azotemia, hypochloremia, and hypokalemia
were common laboratory findings. At surgery, 3 cattle
with an AV or RDA had a ruptured abomasum. Of the
remaining 15 cattle, 12 survived.
Conclusions—Clinical course in beef cattle with an
AV or RDA was more protracted than that typically
associated with these conditions in dairy cattle, but
survival rate in beef cattle that did not have rupture of
the abomasum was sim ilar to that of dairy cattle.
Clinical Relevance—Abomasal displacement should
be considered for beef cattle with abdominal distention.
Prognostic indicators recommended for use in
dairy cattle may not be useful for beef cattle. (J Am
Vet Med Assoc 2000;216:730–733)
Objective—To evaluate the effect of erythromycin on
motility of the ileum, cecum, and pelvic flexure of horses
during the postoperative and post-recovery periods.
Animals—8 healthy adult horses.
Procedure—Horses were anesthetized and bipolar
electrodes were implanted in smooth muscle of the
ileum, cecum, and pelvic flexure. Approximately 4, 16,
and 24 hours (postoperative recording sessions) and
at least 8 days (post-recovery recording session) after
surgery, myoelectric activity was recorded before and
after administration of erythromycin (0.5 mg/kg).
Results—Following erythromycin administration,
myoelectric activity was increased in the ileum during
all postoperative recording sessions but not during
the post-recovery recording session. Myoelectric
activity was increased in the cecum following erythromycin
administration only during the post-recovery
recording session. Myoelectric activity was
increased in the pelvic flexure following erythromycin
administration during all recording sessions. During
several recording sessions, there were short periods
during which myoelectric activity was significantly
decreased following erythromycin administration.
Conclusions and Clinical Relevance—Results suggest
that erythromycin has an effect on myoelectric
activity of the ileum, cecum, and pelvic flexure in
horses; however, prokinetic effects of erythromycin
administered during the postoperative period were
not always the same as effects obtained when the
drug was administered after horses had recovered
from the effects of surgical implantation of recording
devices. Therefore, caution must be exercised when
extrapolating results of prokinetic studies in healthy
animals to animals with abnormal gastrointestinal
tract motility. (Am J Vet Res 2000;61:420–424)
Objective—To evaluate effects of IV administration of
penicillin G potassium (KPEN) or potassium chloride
(KCl) on defecation and myoelectric activity of the
cecum and pelvic flexure of horses.
Animals—5 healthy horses.
Procedure—Horses with 12 bipolar electrodes on the
cecum and pelvic flexure received KPEN or KCl solution
by IV bolus 4 hours apart. Each horse received
the following: 2 × 107 U of KPEN (high-dose KPEN) followed
by 34 mEq of KCl (high-dose KCl), 1 × 107 U of
KPEN (low-dose KPEN) followed by 17 mEq of KCl
(low-dose KCl), high-dose KCl followed by high-dose
KPEN, and low-dose KCl followed by low-dose KPEN.
Number of defecations and myoelectric activity were
recorded for 60 minutes. The first three 5-minute segments
and first four 15-minute segments of myoelectric
activity were analyzed.
Results—Number of defecations during the first 15-
minute segment was greater after high-dose KPEN
treatment than after high-dose or low-dose KCl treatment.
Compared with reference indexes, myoelectric
activity was greater in the pelvic flexure for the first 5-
minute segment after high-dose KCl treatment, in the
cecum and pelvic flexure for the first 5-minute segment
and in the pelvic flexure for the first 15-minute
segment after low-dose KPEN treatment, and in the
pelvic flexure for the first and second 5-minute segments
and the first three 15-minute segments after
high-dose KPEN treatment.
Conclusions and Clinical Relevance—IV administration
of KPEN stimulates defecation and myoelectric
activity of the cecum and pelvic flexure in horses.
Effects of KPEN may be beneficial during episodes of
ileus. (Am J Vet Res 2003;64:1360–1363)
Objective—To evaluate the seroprevalence of paratuberculosis by use of 2 commercial ELISAs in association with prevalence of fecal shedding of mycobacteria within beef cattle herds.
Design—Cross-sectional field study.
Animals—Six beef herds (affected herds; 522 cattle) with and 3 geographically matched herds (181 cattle) without high seroprevalence of paratuberculosis.
Procedures—Blood and fecal samples were collected from adult cattle and assessed for serum anti–Mycobacterium avium subsp paratuberculosis (MAP) antibodies with 2 commercial ELISA kits and submitted for bacterial culture for MAP and environmental bacteria (termed environmental mycobacteria) via a radiometric method, respectively. Species of mycobacterial isolates were identified, and sensitivities and specificities of the 2 ELISAs were compared.
Results—Compared with comparison cattle, cattle from affected herds were 9.4 times as likely to have environmental mycobacteria isolated from feces. Among the 6 affected and 3 comparison herds, the proportions of cattle shedding environmental mycobacteria were 0.225 (range, 0.1 to 0.72) and 0.04 (range, 0 to 0.06), respectively. Although relative MAP-detection specificities (compared with bacterial culture of feces) were different between the 2 ELISAs, sensitivities were not. Nine environmental mycobacterial species were iden-tified from participating herds. All affected herds apparently had ≥ 1 bovid infected with MAP, although MAP was not isolated from any cattle in comparison herds.
Conclusions and Clinical Relevance—In beef herds with persistently high rates of false-positive ELISA results, which may be associated with recovery of environmental myco-bacteria from feces, organism detection via bacterial culture of feces or PCR assay should direct paratuberculosis control measures.
Objective—To develop a better system for classification of herd infection status for paratuberculosis (Johne's disease [JD]) in US cattle herds on the basis of the risk of potential transmission of Mycobacterium avium subsp paratubeculosis.
Sample—Simulated data for herd size and within-herd prevalence; sensitivity and specificity for test methods obtained from consensus-based estimates.
Procedures—Interrelationships among variables influencing interpretation and classification of herd infection status for JD were evaluated by use of simulated data for various herd sizes, true within-herd prevalences, and sampling and testing methods. The probability of finding ≥ 1 infected animal in herds was estimated for various testing methods and sample sizes by use of hypergeometric random sampling.
Results—2 main components were required for the new herd JD classification system: the probability of detection of infection determined on the basis of test results from a sample of animals and the maximum detected number of animals with positive test results. Tables were constructed of the estimated probability of detection of infection, and the maximum number of cattle with positive test results or fecal pools with positive culture results with 95% confidence for classification of herd JD infection status were plotted. Herd risk for JD was categorized on the basis of 95% confidence that the true within-herd prevalence was ≤ 15%, ≤ 10%, ≤ 5%, or ≤ 2%.
Conclusions and Clinical Relevance—Analysis of the findings indicated that a scientifically rigorous and transparent herd classification system for JD in cattle is feasible.
Objective—To determine concentrations of 2 acute-phase
proteins (serum amyloid A [SAA] and
lipopolysaccharide-binding protein [LBP]) in serum
samples obtained from horses with colic and identify
relationships among these acute-phase proteins and
Animals—765 horses with naturally developing gastrointestinal
tract diseases characterized by colic (ie,
clinical signs indicative of abdominal pain) and 79
healthy control horses; all horses were examined at 2
university teaching hospitals.
Procedure—Serum concentrations of SAA and LBP
were determined by immunoturbidometric and dotblot
Results—SAA and LBP concentrations were determined
for 718 and 765 horses with colic, respectively.
Concentrations of SAA were significantly higher in
nonsurvivors than in survivors, and horses with
enteritis or colitis and conditions characterized by
chronic inflammation (eg, abdominal abscesses, peritonitis,
or rectal tears) had SAA concentrations significantly
greater than those for horses with other conditions.
Serum concentrations of LBP did not correlate
with outcome, disease process, or portion of the
gastrointestinal tract affected.
Conclusions and Clinical Relevance—Circulating
concentrations of SAA were significantly higher at
admission in horses with colic attributable to conditions
having a primary inflammatory cause (eg, enteritis,
colitis, peritonitis, or abdominal abscesses) and
were higher in horses that failed to survive the
episode of colic, compared with concentrations in
horses that survived. Serum concentrations of LBP
did not correlate with survival. Analysis of these findings
suggests that evaluation of SAA concentrations
may be of use in identifying horses with colic attributable
to diseases that have inflammation as a primary
component of pathogenesis. (Am J Vet Res
Objective—To determine the pharmacokinetics and clinical effects of a subanesthetic, continuous rate infusion of ketamine administered to healthy awake horses.
Animals—8 adult horses.
Procedures—Ketamine hydrochloride was administered to 2 horses, in a pilot study, at rates ranging from 0.4 to 1.6 mg/kg/h for 6 hours to determine an appropriate dose that did not cause adverse effects. Ketamine was then administered to 6 horses for a total of 12 hours (3 horses at 0.4 mg/kg/h for 6 hours followed by 0.8 mg/kg/h for 6 hours and 3 horses at 0.8 mg/kg/h for 6 hours followed by 0.4 mg/kg/h for 6 hours). Concentration of ketamine in plasma, heart rate, respiratory rate, blood pressure, physical activity, and analgesia were measured prior to, during, and following infusion. Analgesic testing was performed with a modified hoof tester applied at a measured force to the withers and radius.
Results—No signs of excitement and no significant changes in the measured physiologic variables during infusion rates of 0.4 and 0.8 mg of ketamine/kg/h were found. At 6 hours following infusions, heart rate and mean arterial pressure were decreased, compared with preinfusion measurements. An analgesic effect could not be demonstrated during or after infusion. Pharmacokinetic variables for 0.4 and 0.8 mg/kg/h infusions were not significantly different.
Conclusions and Clinical Relevance—Ketamine can be administered to awake horses at 0.4 or 0.8 mg/kg/h without adverse behavioral effects. The observed pharmacokinetic values are different than those reported for single-dose IV bolus administration of this drug.
Objective—To evaluate the correlation between halftime
of liquid-phase gastric emptying (T50), determined
with nuclear scintigraphy using technetium
Tc 99m pentetate, and absorption variables of orally
Animals—6 mature horses.
Procedure—Technetium Tc 99m pentetate (10 mCi)
and acetaminophen (20 mg/kg of body weight) were
administered simultaneously in 200 ml of water. Serial
left and right lateral images of the stomach region
were obtained with a gamma camera, and T50 determined
separately for counts obtained from the left
side, the right side and the geometric mean. Power
exponential curves were used for estimation of T50
and modified R2 values for estimation of goodness of
fit of the data. Serial serum samples were taken, and
acetaminophen concentration was determined, using
fluorescence polarization immunoassay. Maximum
serum concentration (Cmax), time to reach maximum
serum concentration (Tmax), area under the curve for
240 minutes and the absorption constant (Ka) were
determined, using a parameter estimation program.
Correlations were calculated, using the Spearman
rank correlation coefficient.
Results—Correlations between T50 and Tmax and
between T50 and Ka were significant.
Conclusions and Clinical Relevance—Tmax and Ka
are valuable variables in the assessment of liquidphase
gastric emptying using acetaminophen absorption.
Acetaminophen absorption may be a valuable
alternative to nuclear scintigraphy in the determination
of gastric emptying rates in equine patients with
normally functioning small intestine. (Am J Vet Res