Objective—To determine whether the composition
of electrolyte pastes formulated for oral administration
influences voluntary water intake (WI) by horses
recovering from furosemide-induced dehydration.
Procedure—Voluntary WI, body weight, and blood
and urine constituents were measured before and
after induction of dehydration by furosemide administration
and overnight withholding of water; these
same variables also were measured during a 36-hour
rehydration period. Each horse was evaluated 4 times
with random application of 4 treatments (electrolyte
pastes) that provided 0.5 g of KCl/kg of body weight,
0.5 g of NaCl/kg, 0.25 g of NaCl and 0.25 g of KCl/kg,
or no electrolytes (control treatment). Electrolyte
pastes were administered 3 times (4, 8, and 12 hours
after start of the rehydration period).
Results—Administration of all electrolyte pastes
resulted in significantly greater voluntarily WI, compared
with the control treatment, and was accompanied
by significantly greater recovery of body weight
when NaCl was a component of the paste.
Administration of NaCl and NaCl-KCl pastes tended to
produce a state of transient hyperhydration; however,
electrolyte administration also resulted in significantly
greater urine production and electrolyte excretion during
the final 24 hours of the rehydration period.
Adverse effects of oral administration of hypertonic
electrolyte pastes were not observed.
Conclusion and Clinical Relevance—Oral administration
of electrolyte pastes to dehydrated horses
increases voluntary WI and improves rehydration during
the rehydration period. Rehydration is more rapid
and complete when NaCl is a component of the electrolyte
paste. (Am J Vet Res 2002;63:19–27)
Objective—To determine the relationship between
plasma β-endorphin (EN) concentrations and exercise
intensity and duration in horses.
Animals—8 mares with a mean age of 6 years
(range, 3 to 13 years) and mean body weight of 450 kg.
Procedure—Horses were exercised for 20 minutes
at 60% of maximal oxygen consumption (O2max)
and to fatigue at 95% O2max. Plasma EN concentrations
were determined before exercise, after a 10-
minute warmup period, after 5, 10, 15, and 20 minutes
at 60% O2max or at the point of fatigue (95%
O2max), and at regular intervals after exercise.
Glucose concentrations were determined at the
same times EN concentrations were measured.
Plasma lactate concentration was measured 5 minutes
Results—Maximum EN values were recorded 0 to
45 minutes after horses completed each test.
Significant time and intensity effects on EN concentrations
were detected. Concentrations were significantly
higher following exercise at 95% O2max,
compared with those after 20 minutes of exercise at
60% O2max (605.2 ± 140.6 vs 312.3 ± 53.1 pg/ml).
Plasma EN concentration was not related to lactate
concentration and was significantly but weakly correlated
with glucose concentration for exercise at
both intensities (r = 0.21 and 0.30 for 60 and 95%
Conclusions and Clinical Relevance—A critical
exercise threshold exists for EN concentration in
horses, which is 60% O2max or less and is related
to exercise intensity and duration. Even under conditions
of controlled exercise there may be considerable
differences in EN concentrations between
horses. This makes the value of comparing horses
on the basis of their EN concentration questionable.
(Am J Vet Res 2000;61:969–973)
OBJECTIVE To determine effects of anesthesia on plasma concentrations and pulsatility of ACTH in samples obtained from the cavernous sinus and jugular vein of horses.
ANIMALS 6 clinically normal adult horses.
PROCEDURES Catheters were placed in a jugular vein and into the cavernous sinus via a superficial facial vein. The following morning (day 1), cavernous sinus blood samples were collected every 5 minutes for 1 hour (collection of first sample = time 0) and jugular venous blood samples were collected at 0, 30, and 60 minutes. On day 2, horses were sedated with xylazine hydrochloride and anesthesia was induced with propofol mixed with ketamine hydrochloride. Horses were positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen and a continuous rate infusion of butorphanol tartrate. One hour after anesthesia was induced, the blood sample protocol was repeated. Plasma ACTH concentrations were quantified by use of a commercially available sandwich assay. Generalized estimating equations that controlled for horse and an expressly automated deconvolution algorithm were used to determine effects of anesthesia on plasma ACTH concentrations and pulsatility, respectively.
RESULTS Anesthesia significantly reduced the plasma ACTH concentration in blood samples collected from the cavernous sinus.
CONCLUSIONS AND CLINICAL RELEVANCE Mean plasma ACTH concentrations in samples collected from the cavernous sinus of anesthetized horses were reduced. Determining the success of partial ablation of the pituitary gland in situ for treatment of pituitary pars intermedia dysfunction may require that effects of anesthesia be included in interpretation of plasma ACTH concentrations in cavernous sinus blood.
To investigate effects of body condition on permeability of intestinal mucosa in horses.
13 horses (7 obese and 6 lean) from 8 to 15 years of age.
Body condition score was assessed, and an oral sugar test (OST) was performed to evaluate glucose and insulin dynamics. Horses were allowed a 2-week diet acclimation period and were then euthanized. Tissue samples were collected from the jejunum, ileum, cecum, pelvic flexure, right dorsal colon, and rectum. Mucosal permeability was assessed by measuring transepithelial resistance and lipopolysaccharide (LPS) flux across tissue samples mounted in Ussing chambers.
5 obese horses and 1 lean horse had evidence of insulin dysregulation, whereas 1 obese and 5 lean horses had no abnormalities in results of the OST. Results for the OST were not available for 1 obese horse. Mucosal transepithelial resistance did not differ in any intestinal segment between obese and lean horses. Obese horses had a significantly higher LPS flux across jejunal mucosa, compared with results for lean horses, but there were no significant differences between obese and lean horses for other intestinal segments.
CONCLUSIONS AND CLINICAL RELEVANCE
Obese horses may have had greater paracellular mucosal permeability of jejunal mucosa to LPS, compared with that for lean horses. This finding was consistent with data for the gastrointestinal mucosa of humans and mice and supported the hypothesis that obese horses may be at higher risk from chronic exposure to increased amounts of LPS, compared with the risk for lean horses.
Objective—To determine sources of Salmonella
organisms in a veterinary teaching hospital, compare
bacterial culture with polymerase chain reaction (PCR)
testing for detection of Salmonella organisms in environmental
samples, and evaluate the effects of various
disinfectants on detection of Salmonella organisms
on surface materials.
Sample Population—Fecal samples from 638 hospitalized
horses and 783 environmental samples.
Procedure—Standard bacterial culture techniques
were used; the PCR test amplified a segment of the
Salmonella DNA. Five disinfectants were mixed with
Salmonella suspensions, and bacterial culture was
performed. Swab samples were collected from 7 surface
materials after inoculation of the surfaces with
Salmonella Typhimurium, with or without addition of a
disinfectant, and submitted for bacterial culture and
Results—Salmonella organisms were detected in
fecal samples from 35 (5.5%) horses. For environmental
samples, the proportion of positive bacterial
culture results (1/783) was significantly less than the
proportion of positive PCR test results (110/783),
probably because of detection of nonviable DNA by
the PCR test. Detection of Salmonella organisms varied
with the surface material tested, the method of
detection (bacterial culture vs PCR testing), and the
presence and type of disinfectant.
Conclusions and Clinical Relevance—Results of the
present study suggested that Salmonella organisms
can be isolated from feces of hospitalized horses and
a variety of environmental surfaces in a large animal
hospital. Although recovery of Salmonella organisms
was affected by surface material and disinfectant,
bleach was the most effective disinfectant on the
largest number of surfaces tested. (J Am Vet Med
Procedure—Sarcocystis neurona-naïve weanling horses
were randomly allocated to 2 groups. Group A
received pyrantel tartrate at the labeled dose, and
group B received a nonmedicated pellet. Both groups
were orally inoculated with 100 sporocysts/d for 28
days, 500 sporocysts/d for 28 days, and 1,000 sporocysts/
d for 56 days. Blood samples were collected
weekly, and CSF was collected monthly. Ten seronegative
adult horses were monitored as untreated, uninfected
control animals. All serum and CSF samples
were tested by use of western blot tests to detect antibodies
against S neurona. At the end of the study, the
number of seropositive and CSF-positive horses in
groups A and B were compared by use of the Fisher
exact test. Time to seroconversion on the basis of treatment
groups and sex of horses was compared in 2 univariable
Cox proportional hazards models.
Results—After 134 days of sporocyst inoculation, no
significant differences were found between groups A
and B for results of western blot tests of serum or
CSF. There were no significant differences in number
of days to seroconversion on the basis of treatment
groups or sex of horses. The control horses remained
Conclusions and Clinical Relevance—Daily administration
of pyrantel tartrate at the current labeled dose
does not prevent S neurona infection in horses. (Am
J Vet Res 2005;66:846–852)