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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.

Animals—6 horses.

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)

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in American Journal of Veterinary Research


In horses with noninduced, reversible airway obstruction (heaves), pulmonary function is improved after sedation with the α2-adrenergic agonist xylazine. The mechanism of this effect is undetermined. Because the predominant excitatory innervation of equine airways is cholinergic, the influence of α2-adrenergic receptor stimulation on the response of isolated distal airways to cholinergic stimulation was determined. Distal bronchial segments from 22 healthy horses were suspended in isolated organ baths where their mechanical responses to various stimuli could be studied. Each tissue was incubated with one of several concentrations of clonidine, clonidine vehicle, or clonidine plus tolazoline. Then, the contractile response of the tissues to either cumulative acetylcholine (ACh) addition or cumulative electrical field stimulation (efs) was recorded. All contractile responses evoked by efs were mediated through stimulation of cholinergic airway nerves. Clonidine had no effect on the contractile response of distal airway segments to exogenous ACh. However, clonidine (at concentrations > 10-5 M) significantly (P < 0.05) diminished the contractile response of the distal airway segments to efs. This inhibitory effect of clonidine was not observed in the presence of tolazoline. Similar results were observed when the less-selective α2-adrenergic agonist xylazine was exposed to the isolated segments instead of clonidine. Because efs-but not exogenous ACh-induced contractions were inhibited, α2-adrenergic receptor stimulation apparently causes presynaptic inhibition of the cholinergic nerves innervating distal portions of the bronchi of horses.

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in American Journal of Veterinary Research


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.

Design—Prospective study.

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 PCR testing.

ResultsSalmonella 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 Assoc 2001;218:1145–1151)

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in Journal of the American Veterinary Medical Association


Objective—To determine the effects of orally administered glucosamine on concentrations of markers of bone and cartilage metabolism in Standardbred horses during race training.

Animals—Twenty 16- to 20-month-old Standardbreds beginning race training.

Procedure—Horses were randomly assigned to 2 groups. One group received glucosamine hydrochloride (4 g, PO, q 12 h), and the second (control) group received glucose (4 g, PO, q 12 h). Serum samples were obtained prior to onset of the study (baseline) and at regular intervals for 48 weeks for determination of concentrations of keratan sulfate (KS), osteocalcin (OC), and pyridinoline crosslinks (PYD).

Results—Osteocalcin concentrations changed significantly with time; mean serum concentrations were significantly higher than baseline values for samples obtained at 24 to 48 weeks after onset of the study. Although a significant effect of time was observed for mean concentration of KS, concentrations did not differ significantly from baseline values at any time during the study when groups were analyzed separately. However, pooled analysis revealed significant increases of mean serum KS concentration at weeks 24 and 30. Significant changes in serum PYD concentrations were not detected. Oral administration of glucosamine did not significantly affect serum concentrations of any of the markers.

Conclusions and Clinical Relevance—Increased serum OC in clinically normal Standardbreds during race training may reflect bone formation that accompanies adaptive remodeling of the appendicular skeleton. For these experimental conditions, glucosamine did not appear to exert a detectable influence on serum concentrations of these 3 markers of connective tissue metabolism. (Am J Vet Res 2002;63:1106–1110)

Full access
in American Journal of Veterinary Research


Objective—To determine the effects of recombinant equine interleukin -1β (reIL-1β) and 4 anti-inflammatory compounds on the expression and activity of cyclooxygenase (COX)-2 in cultured equine chondrocytes.

Sample Population—Articular cartilage from 9 young adult horses.

Procedure—Reverse transcriptase-polymerase chain reaction methods were used to amplify a portion of equine COX-2 to prepare a cDNA probe. Northern blot analysis was used to quantify the expression of COX-2 in first-passage cultures of equine articular chondrocytes propagated in media containing dexamethasone (DEX), phenylbutazone (PBZ), polysulfated glycosaminoglycan, and hyaluronan, each at concentrations of 10 and 100 µg/ml and each with or without reIL-1β. A commercial immunoassay was used to determine prostaglandin E2 (PGE2) concentrations in conditioned medium of similarly treated cells to quantify COX-2 activity.

Results—Addition of reIL-1β increased the expression of COX-2 in a dose-dependent manner, which was paralleled by an increased concentration of PGE2 in culture medium. Concentration of PGE2 in spent medium from reIL-1β-treated chondrocytes was significantly reduced by DEX and PBZ; however, only DEX significantly reduced gene expression of COX-2.

Conclusions and Clinical Relevance—Prostaglandin E2 is considered to be an important mediator in the pathophysiologic processes of arthritis, and cultured chondrocytes respond to interleukin-1 with enhanced expression and activity of COX-2. Palliative relief in affected horses is probably attributable, in part, to inhibition of PGE2 synthesis; however, analysis of these data suggests that of the 4 compounds tested, only DEX affects pretranslational regulation of the COX-2 gene in cultured equine chondrocytes. (Am J Vet Res 2002;63:1134–1139)

Full access
in American Journal of Veterinary Research