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 identify farm characteristics and management
practices associated with development of
Rhodococcus equi pneumonia in foals.
Design—Prospective case-control study.
Animals—5,230 foals on 138 breeding farms with
Procedure—During 2003, participating veterinarians
provided data from 1 or 2 farms with ≥ 1 foal with
R equi pneumonia and unaffected farms. Data from
affected and unaffected farms were compared by use
of logistic regression analysis.
Results—A number of variables relating to farm size
and desirable management practices were significantly
associated with increased odds of farms being
affected with R equi pneumonia. By use of multivariate
logistic regression, affected farms were determined
significantly more likely to have raised Thoroughbreds,
housed ≥ 15 foals, used concrete floors in foaling stalls,
and tested foals for passive transfer of immunity than
unaffected farms. These results remained significant
even after accounting for exposure of foals to other
breeding farms during the first month of life.
Conclusions and Clinical Relevance—Breeding
farms with large acreage and a large number of mares
and foals have greater odds of being affected by
R equi pneumonia. Clinical relevance of associations
with Thoroughbred breed and concrete flooring in
foaling stalls remains uncertain. Desirable management
factors commonly used on farms were not
effective for controlling or preventing development of
R equi pneumonia. This finding indicates a need to
focus on host factors that influence disease development.
(J Am Vet Med Assoc 2005;226:404–413)
Objective—To determine the types of musculoskeletal
problems that result in lameness or poor performance
in horses used for team roping and determine
whether these problems are different in horses used
for heading versus heeling.
Procedure—Medical records of team roping horses
that were evaluated because of lameness or poor performance
were reviewed to obtain information
regarding signalment, primary use (ie, head horse or
heel horse), history, results of physical and lameness
examinations, diagnostic tests performed, final diagnosis,
Results—Among horses evaluated by lameness clinicians,
the proportion with lameness or poor performance
was significantly greater in horses used for
heading (74/118) and lower in horses used for heeling
(44/118) than would be expected under the null
hypothesis. Most horses examined for poor performance
were lame. A significantly greater proportion
of horses used for heading had right forelimb lameness
(26/74 [35%]), compared with horses used for
heeling (7/44 [16%]). Horses used for heading had
more bilateral forelimb lameness (18/74 [24%]), compared
with horses used for heeling (4/44 [9%]).
Horses used for heeling had more bilateral hind limb
lameness (3/44 [7%]), compared with horses used for
heading (0%). The most common musculoskeletal
problems in horses used for heading were signs of
pain limited to the distal sesamoid (navicular) area,
signs of pain in the navicular area plus osteoarthritis
of the distal tarsal joints, and soft tissue injury in the
forelimb proximal phalangeal (pastern) region. Heeling
horses most commonly had signs of pain in the navicular
area, osteoarthritis of the metatarsophalangeal
joints, and osteoarthritis of the distal tarsal joints.
Conclusions and Clinical Relevance—Horses used
for heading were most commonly affected by lameness
in the right forelimb. Horses used for heeling had
more bilateral hind limb lameness than horses used for
heading. (J Am Vet Med Assoc 2005;226:1694–1699)
Objective—To identify foal-related risk factors associated
with development of Rhodococcus equi pneumonia
among foals on farms with endemic R equi
Design—Prospective case-control study.
Animals—220 foals at 2 equine breeding farms in
Texas during a 2-year period.
Procedure—Information collected for each dam
included age, time housed on the farm prior to parturition,
whether there were any peripartum illnesses,
parity, and health of previous foals. Information collected
for each foal included breed, sex, gestational
age, month and year of birth, location of birth, type of
flooring and bedding in stall, postpartum management
and preventive health care, passive immunity
status, supplementation of immunoglobulins, exposure
to other farms or foals affected with R equi pneumonia,
stall and pasture exposure, commingling with
other mare-foal pairs, age at weaning, and whether
the foal developed R equi pneumonia.
Results—32 of the 220 (15%) foals developed R equi pneumonia, of which 4 (13%) died. Foals at 1 of the 2
farms and foals born during the second year of the
study were more likely to develop R equi pneumonia.
Foal-related factors that were examined were not significantly
associated with risk of R equi pneumonia in
Conclusions and Clinical Relevance—Results suggest
that there are farm- and year-related effects on
the risk that foals will develop R equi pneumonia.
Other foal-related factors significantly associated with
R equi pneumonia were not identified. (J Am Vet Med
Objective—To identify types of musculoskeletal
problems associated with lameness or poor performance
in horses used for barrel racing.
Design—Retrospective case series.
Procedure—Medical records were reviewed for information
on signalment, history, physical and lameness
examination findings, diagnostic tests performed,
diagnosis, and treatment.
Results—Most horses were examined because of
lameness (n = 72 [61%]) rather than poor performance
(46 [39%]), but owner complaint was not significantly
associated with age or body weight of the
horse. The most common performance change was
refusal or failure to turn properly around the first barrel
(19/46 [41%]). The right forelimb (n = 57 [48%])
was most commonly affected, followed by the left
forelimb (51 [43%]), the left hind limb (31 [26%]), and
the right hind limb (25 [21%]). In 31 horses (26%),
both forelimbs were affected, and in 6 (5%), both hind
limbs were affected. The most common musculoskeletal
problems were forelimb foot pain only (n =
39 [33%]), osteoarthritis of the distal tarsal joints (17
[14%]), suspensory ligament desmitis (15 [13%]),
forelimb foot pain with distal tarsal joint osteoarthritis
(11 [9%]), and bruised feet (10 [8.5%]). In 81 (69%)
horses, the affected joint was treated with intra-articular
Conclusions and Clinical Relevance—Results suggest
that in horses used for barrel racing that are
examined because of lameness or poor performance,
the forelimbs are more likely to be affected than the
hind limbs, with forelimb foot pain and osteoarthritis
of the distal tarsal joints being the most common
underlying abnormalities. (J Am Vet Med Assoc 2005;
Objective—To determine the chemoprophylactic effect of gallium maltolate on the cumulative incidence of pneumonia caused by Rhodococcus equi infection in foals.
Animals—483 foals born and raised on 12 equine breeding farms with a history of endemic R equi infections.
Procedures—Group 1 foals were treated with a placebo and group 2 foals were treated with gallium maltolate (approx 30 mg/kg, PO, q 24 h) during the first 2 weeks after birth. Foals were monitored for development of pneumonia attributable to R equi infection and for adverse effects of gallium maltolate.
Results—There were no significant differences in the cumulative incidence of R equi pneumonia among the 2 groups.
Conclusions and Clinical Relevance—Chemoprophylaxis via gallium maltolate administered orally at approximately 30 mg/kg daily for the first 2 weeks after birth failed to reduce the cumulative incidence of pneumonia attributable to R equi infection among foals on breeding farms with endemic R equi infections. Further investigation is needed to identify strategies for control of R equi infections.
Objective—To determine the pharmacokinetics of gallium maltolate (GaM) after intragastric administration in adult horses.
Animals—6 adult horses.
Procedures—Feed was withheld for 12 hours prior to intragastric administration of GaM (20 mg/kg). A single dose of GaM was administered to each horse via a nasogastric tube (time 0). Blood samples were collected at various time points from 0 to 120 hours. Serum was used to determine gallium concentrations by use of inductively coupled plasma-mass spectroscopy. Noncompartmental and compartmental analyses of serum gallium concentrations were performed. Pharmacokinetic models were selected on the basis of the Akaike information criterion and visual analysis of plots of residuals.
Results—Serum concentration data for 1 horse were such that this horse was considered an outlier and excluded from noncompartmental and compartmental analyses. Noncompartmental analysis was used to determine individual pharmacokinetic parameters. A 1-compartment model with first-order input and output and lag time was selected as the best-fit model for the data and used to determine mean — SD values for maximum observed serum concentration (0.28 — 0.09 μg/mL), time of maximum concentration (3.09 — 0.43 hours), time to the first measurable concentration (0.26 — 0.11 hours), apparent elimination half-life (48.82 — 5.63 hours), area under the time-concentration curve (20.68 — 757 h—μg/mL), and apparent volume of distribution (73,493 — 18,899 mL/kg).
Conclusion and Clinical Relevance—Further studies are necessary to determine the bioavailability of GaM after intragastric administration in adult horses.
Objective—To determine whether the concentrations of airborne virulent Rhodococcus equi in stalls housing foals during the first 2 weeks after birth are associated with subsequent development of R equi pneumonia in those foals.
Sample—Air samples collected from foaling stalls and holding pens in which foals were housed during the first 2 weeks after birth.
Procedures—At a breeding farm in Texas, air samples (500 L each) were collected (January through May 2011) from stalls and pens in which 121 foals were housed on day 1 and on days 4, 7, and 14 after birth. For each sample, the concentration of airborne virulent R equi was determined with an immunoblot technique. The association between development of pneumonia and airborne R equi concentration was evaluated via random-effects Poisson regression analysis.
Results—Some air samples were not available for analysis. Of the 471 air samples collected from stalls that housed 121 foals, 90 (19%) contained virulent R equi. Twenty-four of 121 (20%) foals developed R equi pneumonia. Concentrations of virulent R equi in air samples from stalls housing foals that developed R equi pneumonia were significantly higher than those in samples from stalls housing foals that did not develop pneumonia. Accounting for disease effects, air sample concentrations of virulent R equi did not differ significantly by day after birth or by month of birth.
Conclusions and Clinical Relevance—Exposure of foals to airborne virulent R equi during the first 2 weeks after birth was significantly (and likely causally) associated with development of R equi pneumonia.
OBJECTIVE To determine the effects of oral omeprazole administration on the fecal and gastric microbiota of healthy adult horses.
ANIMALS 12 healthy adult research horses.
PROCEDURES Horses were randomly assigned to receive omeprazole paste (4 mg/kg, PO, q 24 h) or a sham (control) treatment (tap water [20 mL, PO, q 24 h]) for 28 days. Fecal and gastric fluid samples were collected prior to the first treatment (day 0), and on days 7, 28, 35, and 56. Sample DNA was extracted, and bacterial 16S rRNA gene sequences were amplified and sequenced to characterize α and β diversity and differential expression of the fecal and gastric microbiota. Data were analyzed by visual examination and by statistical methods.
RESULTS Composition and diversity of the fecal microbiota did not differ significantly between treatment groups or over time. Substantial variation in gastric fluid results within groups and over time precluded meaningful interpretation of the microbiota in those samples.
CONCLUSIONS AND CLINICAL RELEVANCE Results supported that omeprazole administration had no effect on fecal microbiota composition and diversity in this group of healthy adult horses. Small sample size limited power to detect a difference if one existed; however, qualitative graphic examination supported that any difference would likely have been small and of limited clinical importance. Adequate data to evaluate potential effects on the gastric microbiota were not obtained. Investigations are needed to determine the effects of omeprazole in horses with systemic disease or horses receiving other medical treatments.
OBJECTIVE To compare bony changes of the third metacarpal bone (MC3) of Thoroughbred racehorse cadavers with (cases) or without (controls) catastrophic condylar fracture by use of standing MRI.
SAMPLE 140 forelimbs from 26 case horses (both forelimbs) and 88 control horses (single forelimb).
PROCEDURES Bone marrow lesions (BMLs), identified as a decrease in T1-weighted (T1W) signal and increases in T2*-weighted (T2*W) and short tau inversion recovery (STIR) signals, and dense bone volume percentage (DBVP), identified as decreases in T1W, T2*W, and STIR signals, in the distopalmar aspect of MC3 were recorded. Logistic regression was used to compare fractured and nonfractured limbs of cases and fractured limbs of cases with randomly selected limbs of controls.
RESULTS Among cases, fractured limbs were significantly more likely to have BMLs (26/26 [100%]) than were nonfractured limbs (7/26 [27%]). Fractured limbs of cases were significantly more likely to have BMLs (26/26 [100%]) than were limbs of controls (6/88 [7%]). Among cases, there was no significant difference in DBVP between fractured and nonfractured limbs in lateral (26% vs 21%, respectively) or medial (25% vs 20%, respectively) condyles. However, DBVP was significantly greater in fractured limbs of cases than in limbs of controls for lateral (26% vs 16%, respectively) and medial (25% vs 18%, respectively) condyles.
CONCLUSIONS AND CLINICAL RELEVANCE Standing MRI revealed a significantly greater degree of bone change in racehorses with condylar fracture when comparing fractured and nonfractured limbs of case horses and fractured limbs of case horses with randomly selected limbs of control horses.