Equine Veterinary Journal最新文献

Background: Dobutamine is a first-line therapy for hypotension in anaesthetised horses, but the effects on haemodynamic parameters in standing and anaesthetised horses are not well studied.

Objectives: To investigate the effects of dobutamine in escalating dosages on haemodynamic performance in awake and anaesthetised horses.

Study design: Randomised cross-over experimental study.

Methods: Six healthy adult horses were enrolled, including both standing and isoflurane-anaesthetised experiments with 1-week washout. Heart rate, mean arterial pressure (MAP), central venous pressure, pulmonary arterial pressure, and thermodilution cardiac output (CO) were measured at baseline and at dobutamine infusion rates of 0.5, 1, and 2 mcg/kg/min. Arterial and mixed-venous blood was sampled, and oxygen delivery (DO₂), oxygen extraction ratio (O₂ ER), and fShunt were calculated. After confirming normal distribution, variables were compared with baseline and between groups using two-factorial ANOVA (alpha = 5%).

Results: MAP increased significantly during dobutamine infusion in both groups (Standing 92 ± 8 to 119 ± 8 mmHg, p < 0.001; Anaesthetised 58 ± 12 to 91 ± 16 mmHg, p < 0.001), and was significantly higher in awake versus anaesthetised horses at all time points (p < 0.001). CO increased significantly during dobutamine infusion (Standing 39 ± 5 to 68 ± 5 L/min, p < 0.001; Anaesthetised 21 ± 2 to 38 ± 3 L/min, p < 0.001), and was significantly higher in standing horses (p < 0.001). DO₂ (p < 0.001) increased significantly, and O₂ ER (p < 0.001) decreased significantly in both groups with dobutamine infusion. FShunt (p = 0.02) decreased significantly during dobutamine infusion in anaesthetised horses.

Main limitations: Small sample size; study performed in a lateral recumbency.

Conclusions: Dobutamine produces a dose-dependent increase in CO and MAP and improves DO₂ under standing and isoflurane-anaesthetised conditions. Dobutamine dosages of 2 mcg/kg/min reach standing baseline MAP and CO.

Background: Organic dust from hay is a primary trigger of equine asthma.

Objectives: (1) To introduce a novel hay-shaker (HS) device for standardised hay dust generation, enabling simultaneous measurements of various particulate matter (PM) size fractions. (2) To compare these measurements with those in the horse's breathing zone (BZ) to assess the influence of environmental and individual factors.

Study design: Comparative experimental study.

Methods: A HS generating dust was developed. Total dust (PMT) and size fractions (PM1, PM2.5, PM4 and PM10, representing particle size in μm) were measured from 50 hay samples provided by clients using an aerosol monitor (DustTrak DRX 8534) in the HS (HS-PMx) and the BZ (BZ-PMx) of 50 horses (26 healthy, 24 asthmatic) during hay feeding. Linear regression analysis evaluated the relationship between HS-PMx and ln BZ-PMx for each fraction, accounting for environmental (humidity, temperature) and individual factors (horse characteristics and feeding behaviour, assessed with the Hay Contact Score).

Results: The HS generated measurable dust across all PM sizes. Regression models explained 69% to 73% of ln BZ-PMx variance, showing a weak positive association between HS-PMx and ln BZ-PMx across all size fractions. Hay Contact Score had the strongest positive association with ln BZ-PMx. Cohort, ambient temperature and humidity were negatively associated with ln BZ-PMx for certain particle sizes. The final model, incorporating HS-PM4, Hay Contact Score, cohort, temperature, and humidity as predictors, demonstrated robust predictive accuracy for BZ-PM4 (adjusted R² = 0.73).

Main limitations: Clinical impact of hay dust and poor-quality hay was not assessed.

Conclusions: The HS reliably generates hay dust for measuring standard PM fractions, particularly respirable PM4, critical to equine respiratory health. BZ dust concentrations are significantly influenced by feeding behaviour. The HS offers a standardised method for assessing hay quality, enabling informed decisions on hay selection to support respiratory health in stabled horses.

Background: Exercising arrhythmias are common in horses participating in eventing competitions. Heart rate variability (HRV) and a specific measure of the degree of heart rate fluctuation (Detrended Fluctuation Analysis alpha1; DFA-α1) are proposed as exercise intensity and fatigue markers.

Objectives: (1) To describe exercising arrhythmias and DFA-α1 values during 2-4* level eventing cross-country competitions in horses from two European countries; (2) to identify associations between exercising arrhythmias, DFA-α1 and competition results and (3) to evaluate whether markers of the intensity of exercise are associated with exercising arrhythmias, DFA-α1 or competition results.

Methods: A convenience sample of exercising ECGs and competition results from horses during cross-country eventing competitions was examined. Statistical analysis was conducted using multivariable mixed-effects logistic, Poisson and linear regression models.

Results: Arrhythmias were frequent during 69 cross-country competition ECGs from 43 horses. Detrended fluctuation analysis α1 was not associated with performance during cross-country, but a higher DFA-α1 during cross-country was associated with fewer showjumping phase penalties. More premature complexes, the presence of complex arrhythmias and arrhythmias during recovery were associated with fewer time penalties during cross-country. The presence of complex arrhythmias and arrhythmias during recovery of the cross-country phase was associated with more penalties during the showjumping phase. Higher blood lactate concentration, higher HR_peak and higher HR_mean were associated with fewer time penalties during cross-country.

Main limitations: The arrhythmias observed do not allow conclusions to be drawn about the consequences of more severe arrhythmias. The associations described here were often of small magnitude or with large confidence intervals and must be interpreted cautiously.

Conclusions: Arrhythmias during the cross-country test of eventing competitions were frequently associated with positive competition results during the cross-country phase and negative results during the showjumping phase. The specific arrhythmia types and circumstances that should raise concern about performance and safety remain relevant but unanswered questions for equine practitioners.

Background: Strangulating lipomata are the most common cause of small intestinal strangulating obstruction. Evaluation of histological features of pathological and non-pathological lipomata, and the histological properties of omental and retroperitoneal fat have not been described.

Objectives: To characterise histological features of equine abdominal lipomata, omental and retroperitoneal adipose tissue, and associations between them.

Study design: Prospective observational anatomic (gross and histological).

Methods: Horses undergoing emergency laparotomy for management of abdominal pain in a single hospital were recruited. Signalment was recorded. Gross features of lipomata that were a cause of strangulating obstruction (pathological lipomata [PAL]), and lipomata that were currently not causing an intestinal obstruction (pedunculated [PEL] or non-pedunculated [NPL]) were recorded. Lipomata that were removed intra-operatively, or following owner-requested euthanasia, as well as omentum or retroperitoneal adipose tissue, where excised routinely as part of routine management (or post-euthanasia) were fixed in 10% neutral-buffered formalin prior to staining (haematoxylin and eosin, picrosirius red). Descriptive statistical analyses were performed. Pearson's chi-square, Fisher's exact or Kruskal-Wallis tests, as appropriate, were used to assess associations. Significance was p < 0.05.

Results: Seventy-four horses were enrolled; 71 lipomata, 48 retroperitoneal adipose samples, and 26 omental samples underwent evaluation. Increasing age was predictive of lipomata presence and PAL/PEL. Neither omental nor retroperitoneal adipose tissue histological features were correlated with lipomata presence or type. PAL were more likely to exhibit capsule formation (PAL: 70%, NPL: 42%, p = 0.03), and had a higher vascular density (median 10.6; IQR: 8.8-16.8; p = 0.05), compared with NPL. PEL were more likely to exhibit steatonecrosis (PEL: 92%, NPL: 33%, p = 0.01) and had increased mineralisation (PEL: 67%, NPL: 17%, p = 0.05) compared with NPL.

Main limitations: Small sample size.

Conclusions: Histological features of omental and retroperitoneal fat do not predict presence of lipomata or type. However, there are histological features of PAL and PEL which may be related to pathological potential.

Background: Changes in the third metacarpal (MC3) mid-diaphyseal dimensions were measured radiographically in young Thoroughbred racehorses through race training and found to be associated with a higher risk of shin soreness. However, it is still unclear whether such negative MC3 morphologies are set congenitally or through development.

Objective: To quantify MC3 bone dimensional changes through growth.

Study design: Longitudinal.

Method: Twenty privately owned Thoroughbred foals were radiographed bimonthly from birth to 14 months of age. Four linear MC3 parameters (proximodistal MC3 length, mid-diaphyseal dorsal and palmar cortical bone thickness, and dorsopalmar medullary width) were measured using ImageJ on lateromedial radiographs. Associations with age (growth), MC3 length, differences between left and right limbs, and between sexes were analysed separately using a linear mixed effects model.

Results: The dorsal cortical bone thickness showed a positive linear relationship with growth (0.4 $\pm$ 0.02 mm per month, p < 0.001, 95% CI [0.37, 0.44]) while the medullary width did not change. The relative thickness of the dorsal cortical bone thickness compared with the medullary cavity width and palmar cortical bone thickness also increased through growth (0.2 $\pm$ 0.01 mm per month, p < 0.001, 95% CI [0.14, 0.19]). The dorsal cortical bone thickness was positively associated with MC3 length (0.07 $\pm$ 0.0001 mm per mm increase in MC3 length, p < 0.001, 95% CI [0.05, 0.08]) and the relative thickness of the dorsal cortical bone thickness (RI) to the rest of the diaphyseal parameters (0.02 $\pm$ 0.01 per mm increase in MC3 length, p = 0.01, 95% CI [0.01, 0.03]).

Main limitations: A limited number of foals were included with similar breeding.

Conclusion: The mid-diaphyseal dorsal cortical bone thickness and proportions could be measured to monitor musculoskeletal development and identify foals at increased risk of shin soreness or those that are immature or otherwise need more time before the commencement of fast training.

Background: Equine osteoarthritis (OA) is predominantly diagnosed through clinical examination and radiography, leading to detection only after significant joint pathology. The pathogenesis of OA remains unclear and while many medications modify the disease's inflammatory components, no curative or reversal treatments exist. Identifying differentially abundant metabolites and proteins correlated with osteoarthritis severity could improve early diagnosis, track disease progression, and evaluate responses to interventions.

Objectives: To identify molecular markers of osteoarthritis severity based on histological and macroscopic grading.

Study design: Cross-sectional study.

Methods: Post-mortem synovial fluid was collected from 58 Thoroughbred racehorse joints and 83 joints from mixed breeds. Joints were histologically and macroscopically scored and categorised by OA and synovitis grade. Synovial fluid nuclear magnetic resonance metabolomic and mass spectrometry proteomic analyses were performed, individually and combined.

Results: In Thoroughbreds, synovial fluid concentrations of metabolites 2-aminobutyrate, alanine and creatine were elevated for higher OA grades, while glutamate was reduced for both Thoroughbreds and mixed breeds. In mixed breeds, concentrations of three uncharacterised proteins, lipopolysaccharide binding protein and immunoglobulin kappa constant were lower for higher OA grades; concentrations of an uncharacterised protein were higher for OA grade 1 only, and apolipoprotein A1 concentrations were higher for OA grades 1 and 2 compared with lower grades. For Thoroughbreds, gelsolin concentrations were lower for higher OA grades, and afamin was lower at a higher synovitis grade. Correlation analyses of combined metabolomics and proteomics datasets revealed 58 and 32 significant variables for Thoroughbreds and mixed breeds, respectively, with correlations from -0.48 to 0.42 and -0.44 to 0.49.

Main limitations: The study's reliance on post-mortem assessments limits correlation with clinical osteoarthritis severity.

Conclusions: Following stratification of equine OA severity through histological and macroscopic grading, synovial fluid metabolomic and proteomic profiling identified markers that may support earlier diagnosis and progression tracking. Further research is needed to correlate these markers with clinical osteoarthritis severity.

Background: Surgical site infection (SSI) is a frequent complication following emergency equine laparotomy, negatively impacting equine welfare, increasing treatment costs and presenting a hospital biosecurity risk.

Objectives: To determine if a sutured-on stent dressing for incisional protection during anaesthetic recovery reduced SSI following emergency laparotomy.

Study design: Randomised controlled trial.

Methods: Eligible horses were randomised to a sutured-on stent (intervention) or textile dressing (control) as the primary component of a 3-layer abdominal bandage placed for anaesthetic recovery. Horses were followed up to 90 days postoperatively. Data were analysed according to intention-to-treat principles. Time to SSI (primary outcome) for each group was analysed using a Cox proportional hazard model. Secondary outcomes (SSI and pyrexia during hospitalisation, days hospitalisation and incisional hernia formation at 90 days) were analysed using Chi-squared tests and a univariable logistic regression model (categorical data) or by comparing means between groups (continuous data).

Results: Of 352 eligible horses enrolled (167 intervention group, 185 control group), SSI developed in 101 (28.7%) at a mean of 9.7 days (SD 4.6 days). Rate of SSI was not significantly different between groups unadjusted (hazard ratio [HR] 0.83, 95% CI 0.56-1.23, p = 0.4) or adjusted for variables significantly associated with rate of SSI (HR 0.88, 95% CI 0.59-1.30, p = 0.5). There were no significant differences in secondary outcomes between intervention and control groups.

Main limitations: Single-centre study evaluating incisional protection from a primary dressing under a secondary adhesive and tertiary fabric abdominal bandage for anaesthetic recovery.

Conclusions: Use of a sutured-on stent compared with a textile adhesive dressing as the primary layer of an abdominal bandage for anaesthetic recovery did not reduce the rate of SSI. Further RCT are warranted to investigate efficacy of other interventions on reduction of SSI following emergency laparotomy in horses.

Background: Surgical site infection (SSI) is an important complication following emergency celiotomy in the horse. Judicious antimicrobial use is important for the prevention of antimicrobial resistance and the limitation of antimicrobial-associated complications. Previous studies in horses have found no association between SSI and perioperative antimicrobial duration, but the ideal duration of antimicrobial administration in horses undergoing exploratory celiotomy remains unclear.

Objective: To compare SSI and describe post-operative complications, survival, duration and cost of hospitalisation in horses receiving one of two antimicrobial protocols following clean or select clean-contaminated emergency exploratory celiotomy.

Study design: Prospective randomised clinical study.

Methods: Adult horses undergoing clean or selected clean-contaminated emergency celiotomy at The University of Georgia Teaching Hospital (2013-2019) were prospectively enrolled and randomised to protocol A (pre- and intra-operative antimicrobials only, n = 39) or protocol B (antimicrobials continued for 72 h of post-operative administration, n = 37). Incisional closure and protection were standardised. The prevalence of SSI was compared between protocols for horses surviving beyond day five of hospitalisation and additional clinical outcomes were described.

Results: Horses in protocol A had an increased prevalence of SSI during hospitalisation compared with protocol B (6/37 [16%] vs. 0/35 [0%]; p = 0.03). The difference was of borderline significance at 4 weeks post-operatively (7/32 [22%] vs. 1/31 [3%]; p = 0.05).

Main limitations: Planned enrolment was not met, providing only enough data for a small study. Numbers were limited by inclusion criteria as well as difficulties regarding owner consent and surgeon-determined enrolment. In light of the low statistical power of the study, results should be used to direct further research, and caution must be taken in applying them to clinical practice.

Conclusions: The difference in hospitalised SSI between groups and the low prevalence of SSI, particularly in the 72-h post-operative group, supports the need for continued research to determine optimal antimicrobial duration and protocols to reduce SSI in horses undergoing exploratory celiotomy.