Prevalence and performance effects of neonatal disease in Thoroughbred and Standardbred foals in South-Eastern Australia.

BACKGROUND: There is little information on foal mortality and the epidemiology of diseases in the neonatal period in Australian equine breeding enterprises. METHODOLOGY: This was a prospective cohort study of 1219 foals on 15 breeding farms in south-eastern Australia to identify the proportion of foals recognised on farm as abnormal at birth or within the first 48 h postpartum, determine the prevalence and risk factors for neonatal disease and assess the subsequent performance of foals in the study population. RESULTS: Overall, 27 foals died within 6 weeks of birth in the study population (2.2%), 142 foals (11.6%) were reported as abnormal at birth, and 304 (25.3%) were regarded as abnormal in the first 48 h postpartum. Non-septic orthopaedic disease (NSOD) was the most common abnormality recognised. Premature foals and foals born after dystocia or abnormal parturition were more likely to have clinical abnormalities recognised, but the intensity of nursing care did not predict outcome. Prophylactic administration of antimicrobial drugs was associated with increased mortality and septic disease. Maternal periparturient problems, foal gender, abnormality at birth and the presence of septic disease or neonatal maladjustment were associated with decreased performance outcomes, whereas measures to assess and augment passive immune transfer were associated with improved athletic performance. CONCLUSIONS AND RELEVANCE: Information in the current study is important for the treatment and management decisions on farm and to identify industry welfare and production priorities. Although the incidence of all outcome variables was variable, factors recognised on farm in the peri-parturient period were predictive of subsequent athletic performance.

Disclosure of disability or misconduct in veterinary graduate registration: balancing confidentiality, equity and stakeholder interests.

BACKGROUND: Veterinary registration processes, including disclosure of disability or misconduct, vary across jurisdictions in Australasia, and there is currently no clear mechanism for the communication of registration requirements to prospective or current students. Procedures for registration of graduating students are evolving but are not necessarily responsive to conflicting imperatives for confidentiality, protection of stakeholder interests and graduate support. OBJECTIVE: To obtain opinions from members of the veterinary profession in Australasia on issues relating to graduate registration, including communication between veterinary schools and registration bodies. METHOD: This was an online survey. RESULTS: Responses were received from 245 members of the profession, including employers, educators, current students, recent graduates and board members. Respondents agreed on the importance of the survey topic to all stakeholder groups, and responses reflected the complex, contestable and nuanced nature of inherent concepts. Responses were strongly polarised between individuals with an appetite for reform, improved discourse around disability and remediation of unprofessional conduct and those with concerns and experiences suggesting boards and educators could not responsibly manage processes that included increased disclosure of disability or prior conduct. CONCLUSION: Issues related to disability and misconduct should be addressed separately in any change to registration processes. A harmonisation of registration processes across jurisdictions is desirable, but the legal implications of any potential changes require careful consideration. There is a need for improved support of disability, remediation of misconduct and a desire to promote diversity within the profession. The survey evoked strong emotions, and future discussion requires sensitivity, empathy and insight.

Chlamydia psittaci infection as a cause of respiratory disease in neonatal foals.

BACKGROUND: During 2016-2018, 15 critically ill neonatal foals with acute respiratory distress associated with Chlamydia psittaci infection were presented to three referral hospitals in New South Wales. Chlamydia psittaci has not previously been associated with the development of neonatal respiratory disease. OBJECTIVES: To investigate and describe the clinical features and outcome of C. psittaci infection in neonatal foals. STUDY DESIGN: Multicentre retrospective case series. METHODS: The clinical, clinicopathological, necropsy and histological features of 15 foals with confirmed C. psittaci infection were reviewed and reported. RESULTS: Thirteen foals with C. psittaci infection died or were subjected to euthanasia within 36 h of hospitalisation and two foals survived to discharge. Findings during post-mortem examination of nonsurviving foals included bronchopneumonia, pulmonary congestion, hepatic congestion and hepatic inflammation. Detection of C. psittaci was achieved using polymerase chain reaction (PCR) testing of swabs of nasal secretions (4/6) and rectal mucosa (5/7) from live foals, lung tissues of foals at necropsy (11/14) and foetal membranes (4/5). MAIN LIMITATIONS: Small numbers of confirmed cases of neonatal C. psittaci infection and inconsistent sampling methods. CONCLUSIONS: Chlamydia psittaci should be considered a differential diagnosis for neonatal foals with signs of severe systemic disease, including equine neonatal acute respiratory distress syndrome (EqNARDS). Chlamydia psittaci is a zoonotic pathogen and a personal protective equipment (PPE) should be worn for the management of foals with suspected or confirmed infection.

The application of faecal egg count results and statistical inference for clinical decision making in foals.

This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC) from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C1), the mean of three (X¯1-3) or nine counts (X¯1-9) and the upper 5% confidence limit of the gamma confidence interval (CI) of the estimate of the distribution mean (µ) from three (UCL1-3) and nine counts (UCL1-9) were determined for a range of egg count thresholds. The UCL1-9 was used as the best estimate of µ, hypothesis testing for treatment and the comparison of treatment decision-making using C1, X¯1-3, X¯1-9 and UCL1-3. The results of this study demonstrated that a point estimate (C1 or X¯1-3) was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C1 compared with UCL1-9. Of the foals with C1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for µ takes this variability into account and is recommended for use when interpreting FEC data from horses.

Antimicrobial stewardship in equine practice.

Antimicrobial stewardship involves the judicious use of antimicrobials balanced against the requirement to treat the presenting clinical condition. The same mandate and principles as discussed in human medicine and other veterinary disciplines are relevant to equine practice. This brief review will focus on available resources for equine practitioners, emerging perspectives on antimicrobial use and stewardship, and opportunities for more effective antimicrobial use in equine practice. There is a need for improved client education, availability of faster and more accurate techniques for identification and sensitivity testing of bacterial pathogens, and the development of novel agents.

Student selection to a rural veterinary school. 2: predictors of student performance and attrition.

OBJECTIVE: To evaluate the extent to which current selection processes at Charles Sturt University, New South Wales, Australia, predict performance within and attrition from the veterinary degree program. DESIGN: Retrospective evaluation of application details and student performance data. METHODS: Database records of 424 students entering the veterinary program were retrieved from university records, including all students graduating (n = 356) or leaving the program without completing (n = 68) between 2005 and 2016. Demographic data were related to results of selection processes and achievement within the degree using univariable and multivariable general linear and logistic regression analyses. RESULTS: The grade point average achieved over the 6 years of the degree was influenced by academic achievement prior to entry, gender (females performed ≈ 2% better than males) and interview scores. Preceptor evaluation of final-year clinical performance was associated with interview scores, gender (males performed ≈ 4% better than females) and residential address at the time of application. Attrition for personal reasons was more common for female students and students who had completed a prior degree, and students who experienced academic or personal attrition had lower written application scores. Factors that have been previously linked to poor academic outcomes, including rural or low socioeconomic background, were not associated with adverse student outcomes. CONCLUSION: Selection processes did not systematically disadvantage students admitted to the degree program. Gender differences in personal attrition and academic and clinical performance warrant further evaluation. Factors in addition to academic aptitude predicted student success.

Student selection to a rural veterinary school. 1: applicant demographics and predictors of success within the application process.

OBJECTIVE: To determine demographic details of applicants to the veterinary degree program at and relate this information to student selection processes. DESIGN: Retrospective evaluation of applicant data. METHODS: Database records of 4042 applicants to the veterinary program (2006-2016) were retrieved from university records. Summary statistics were used to determine basic demographic data, which were related to pre-entry academic achievement and results of selection processes using univariable and multivariable analyses. RESULTS: The number of applications, interviews and acceptance of offers fluctuated but did not vary substantively for the duration of the study. Gender, rurality (as assessed by residential and school postcodes), socioeconomic background, academic background and pre-entry academic achievement all significantly influenced written application and interview scores in the multivariate models. Rural background, written application score, number of applications, pre-entry academic history and achievement significantly affected the chances of receiving an interview. Chances of receiving an offer and subsequent program entry were significantly influenced by academic background, interview score and pre-entry academic achievement. Male applicants were more likely to receive an offer, but gender had no effect on program entry. Rural residential and school background was associated with significantly reduced ATAR in comparison with city-based applicants. CONCLUSION: Selection processes effectively identified applicants with demographic backgrounds and life experiences consistent with the School's commitment to the veterinary needs of rural and regional Australia. Findings support the provision of an academic loading for the ATAR results of rural students. Effects of these selection outcomes on student performance should be evaluated.

Exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 are associated with lower airway inflammation and airway cytology in the horse.

BACKGROUND: Exhaled breath condensate (EBC) analysis is a noninvasive method to assess the lower respiratory tract. In human subjects, EBC hydrogen peroxide (H2 O2 ), pH and leukotriene B4 (LTB4 ) are useful for detection and monitoring of inflammatory lung diseases, including asthma. OBJECTIVES: To determine associations between EBC biomarkers and cytological and endoscopic definitions of lower airway inflammation (LAI) while controlling for sampling and environmental variables. STUDY DESIGN: Prospective, cross-sectional study. METHODS: Clinical, endoscopic and airway cytological findings from 47 horses were compared with EBC pH and concentrations of H2 O2 and LTB4 by univariate and multivariable analyses. Dichotomous (presence/absence of airway inflammation) and continuous outcome variables (differential cell counts in tracheal aspirate and bronchoalveolar lavage fluid, BALF) were evaluated and potential effects of collection and methodological factors were included. RESULTS: EBC pH and H2 O2 concentrations were higher in horses with LAI and both were positively associated with the percentage of neutrophils in BALF (P<0.05). Mast cell percentage in BALF was negatively associated with EBC pH, and BALF eosinophil percentage was positively associated with EBC LTB4 (P<0.05). Ambient temperature, relative humidity and assay methodology significantly impacted some analytes. MAIN LIMITATIONS: LAI is challenging to categorise due to a variety of clinical and cytological phenotypes. Although the study was designed to overcome this limitation, numbers of horses were small in some categories. CONCLUSIONS: EBC pH and H2 O2 concentrations are altered by airway inflammation, suggesting a role for these biomarkers in the diagnosis and monitoring of airway disease. Environmental and methodological factors can influence these biomarkers and should be considered in the interpretation of results.

The consistency and influence of environmental and animal factors on exhaled breath condensate hydrogen peroxide, pH and leukotriene B4 in horses.

This study was performed to determine the consistency of exhaled breath condensate (EBC) hydrogen peroxide (H2O2), pH and leukotriene B4 (LTB4) measurements in asymptomatic horses and to define the influence of environmental and animal factors on these variables. Intra- and inter-day consistency for both H2O2 and pH measurements were adequate, with intraclass correlation coefficients ≥0.8, whereas the consistency for LTB4 was poor. H2O2 was influenced by ambient temperature (TA), humidity, time of day and collection location (all P<0.01), while pH was influenced by respiratory rate during EBC collection and TA (both P<0.001). The consistency of EBC H2O2 and pH measurements may be sufficient for use as diagnostic biomarkers in horses. However, the influence of identified environmental and animal factors should be considered.

Pharmacokinetic and pharmacodynamic effects of two omeprazole formulations on stomach pH and gastric ulcer scores.

REASONS FOR PERFORMING THE STUDY: Limited data are available on the relative pharmacokinetics and pharmacodynamics of different omeprazole formulations. OBJECTIVES: To compare pharmacokinetic and pharmacodynamic effects of a novel omeprazole formulation against a currently registered product. STUDY DESIGN: Masked 2 period, 2 treatment crossover. METHODS: Twelve clinically healthy horses were studied over two 6-day treatment periods. Horses were randomly assigned to receive a novel omeprazole paste (Ulcershield: ULS) or a currently registered reference omeprazole product (OMO). Gastric pH was measured continuously for 10 h on the day prior to commencing treatment (Day -1) and after 6 days of oral treatment (Day 5) using in situ antimony pH probes within an indwelling nasogastric tube. Plasma pharmacokinetics were determined on Days 0 and 6. RESULTS: Treatment significantly (P<0.005) increased gastric pH on Day 5, compared to results obtained prior to treatment (Day -1) and there was no significant difference between products (P = 0.773). Similarly, comparison of median hourly gastric pH (P = 0.593), mean gastric pH (P = 0.154), percentage time pH<4 (P = 0.259) and area under the time-gastric pH response curve (P = 0.734) did not discriminate between products. Both treatments resulted in significantly lower gastric ulcer severity scores (both P = 0.004), with no difference between treatments (P = 0.688). Comparison of mean log area under time-plasma concentration curves demonstrated that, although the lower limit of the 90% confidence interval was within the -20% limit for bioequivalence, the upper limit was exceeded, suggesting that the test product could have greater bioavailability than the reference product. MAIN LIMITATIONS: The small sample size, large interhorse plasma omeprazole concentrations, and low bioavailability of omeprazole impacted the sensitivity of the bioequivalence analysis. CONCLUSIONS: ULS matched or slightly exceeded OMO plasma concentrations. Both products resulted in equivalent increases in gastric pH, gastric pH profiles and decrease in gastric ulcer scores. Thus, ULS was pharmacodynamically equivalent to OMO and was associated with an equivalent beneficial effect on gastric squamous mucosal ulceration.

Effects of sedation and salbutamol administration on hyperpnoea and tidal breathing spirometry in healthy horses.

Sedation is often required to perform pulmonary function testing (PFT) in horses, but drug effects may influence respiratory function. The current study was designed to characterise the effects of sedation and bronchodilator administration on absolute and relative indices of pulmonary function during eupnoeic respiration and carbon dioxide-induced hyperpnoea (rebreathing) in healthy horses using a pneumotachographic spirometry system. Sedation with acetylpromazine (ACP), xylazine, or both drugs in combination was associated with significant reductions in respiratory frequency, minute ventilation and peak airflows during eupnoeic respiration. Peak expiratory airflow occurred later in the respiratory cycle than was observed in untreated horses, and expiratory relative flow-time indices were also affected during eupnoeic respiration. Rebreathing attenuated the effects of sedation on indices of pulmonary function, suggesting that future studies should consider the use of induced hyperpnoea as part of the spirometry protocol. Based on the finding that all sedative agents had some effect on eupnoeic respiration, albeit least pronounced with ACP, the latter drug should be considered for sedation of horses undergoing PFT. Salbutamol increased peak inspiratory flow during eupnoeic respiration in healthy horses.

Demographic and preliminary employment data of the first two graduate cohorts from a rural veterinary school.

OBJECTIVE: To report initial career experiences and graduate employment destinations 1 and 5 years following graduation of the 67 graduates from the first two graduating classes of the veterinary science program at Charles Sturt University. DESIGN: Online survey of graduates from the 2010 and 2011 cohorts undertaken 12 months following course completion and descriptive data on graduate practice locations 5 years post-graduation. PROCEDURE: Questions covered general demographic information, issues relating to work-life balance and factors influencing vocational choices. Descriptive statistics and qualitative responses are reported, with comparisons between continuous variables by two-sample t-test and between categories by Chi-square analyses. Significance was set at P < 0.05. Graduates' locations 5 years after graduation were obtained from veterinary registration details and staff contact with graduates. RESULTS: Complete survey responses were received from 39 graduates of whom 34 were employed in regional areas, 1 in a very remote area, 3 in major cities and 1 overseas. Hours worked and salary received were consistent with other survey data, with new graduates working in regional practices earning slightly more than those working in metropolitan practices. At 5 years following graduation, the majority (56/61, 92%) remained in rural or regional Australian veterinary practices, with a further five graduates overseas and one lost to follow-up. CONCLUSION: This study supported the selection criteria and educational approaches at CSU in establishing most of the new graduates in rural and regional mixed veterinary practice.

Risk factors in equine transport-related health problems: A survey of the Australian equine industry.

BACKGROUND: Transportation can affect equine health and is a potential source of economic loss to the industry. OBJECTIVES: To identify journey (duration, vehicle, commercial or noncommercial) and horse (sex, age, breed, use, amateur or professional status) characteristics associated with the development of transport-related health problems in horses. STUDY DESIGN: Cross-sectional online survey. METHODS: An online survey was conducted targeting amateur and professional participants in the Australian equine industry; eligible respondents were required to organise horse movements at least monthly. Respondents provided details of the last case of a transport-related health problem that had affected their horse(s). Associations between type of health problem, journey and horse characteristics were examined with multivariable multinomial regression analysis. RESULTS: Based on 214 responses, health problems were classified as injuries, muscular problems, heat stroke, gastrointestinal and respiratory problems, and death or euthanasia. Respiratory problems were reported most frequently (33.7%), followed by gastrointestinal problems (23.8%) and traumatic injuries (16.3%). The type of health problem was associated with journey duration (P<0.001) and horse breed (P = 0.001). Injuries were more likely to occur on short journeys, whereas more severe illnesses (gastrointestinal and respiratory problems, and death or euthanasia) were more likely to occur on long journeys. Using Standardbreds as the reference group, Thoroughbreds, Arabians and Warmbloods were more likely to experience a severe illness than an injury. MAIN LIMITATIONS: Self-selected participation in the study and the self-reported nature of transport-related problems. CONCLUSIONS: Horses undertaking journeys of longer than 24 h are at greater risk for the development of severe disease or death. Further studies on long-haul transportation effects are required to safeguard the welfare of horses moved over long distances.

Reliability of breath by breath spirometry and relative flow-time indices for pulmonary function testing in horses.

BACKGROUND: Respiratory problems are common in horses, and are often diagnosed as a cause of poor athletic performance. Reliable, accurate and sensitive spirometric tests of airway function in resting horses would assist with the diagnosis of limitations to breathing and facilitate investigations of the effects of various treatments on breathing capacity. The evaluation of respiratory function in horses is challenging and suitable procedures are not widely available to equine practitioners. The determination of relative flow or flow-time measures is used in paediatric patients where compliance may limit conventional pulmonary function techniques. The aim of the current study was to characterise absolute and relative indices of respiratory function in healthy horses during eupnoea (tidal breathing) and carbon dioxide (CO2)-induced hyperpnoea (rebreathing) using a modified mask pneumotrachographic technique well suited to equine practice, and to evaluate the reliability of this technique over three consecutive days. Coefficients of variation, intra-class correlations, mean differences and 95% confidence intervals across all days of testing were established for each parameter. RESULTS: The technique provided absolute measures of respiratory function (respiratory rate, tidal volume, peak inspiratory and expiratory flows, time to peak flow) consistent with previous studies and there was no significant effect of day on any measure of respiratory function. Variability of measurements was decreased during hyperpnea caused by rebreathing CO2, but a number of relative flow-time variables demonstrated good agreement during eupnoeic respiration. CONCLUSIONS: The technique was well tolerated by horses and study findings suggest the technique is suitable for evaluation of respiratory function in horses. The use of relative flow-time variables provided reproducible (consistent) results, suggesting the technique may be of use for repeated measures studies in horses during tidal breathing or rebreathing.

Survey of horse transportation in Australia: issues and practices.

OBJECTIVE: To survey amateur and professional participants on equine transportation management, practices and outcomes in Australia. METHODS: An online survey targeting people who organised horse movements at least monthly was made available to a broad cross-section of amateur and professional equine associations. Respondents were invited to provide demographic details and information relating to their routine transportation management practices and their experiences of issues relating to the transportation of horses. RESULTS: Of 797 usable responses involving approximately 17,000 horses and 313,000 individual horse transport events, transport-related behavioural problems were reported by 38% of respondents, particularly at loading. Transport-related health problems had been experienced during or after transportation by horses in the care of 67% of respondents. The most common problems reported were traumatic injuries (45.0%), diarrhoea (20.0%), muscular problems (13.0%), respiratory problems (12.3%), overheating (10.5%) and colic (10.3%). In the 2 years reviewed in the survey, 9.4% of participants reported at least one case of transport-associated pneumonia and 35 horses had died, most commonly from fractures, colic or pneumonia. Although respondents identifying as amateurs transported horses less frequently and over shorter distances, the incidence of transport-related problems was similar between amateurs and professionals. Respondents reported specific precautions before, during and after transportation, although management was often not compliant with the Australian Code of horse transportation. CONCLUSIONS: Responses indicated that there remains a substantial risk of adverse welfare and health outcomes for horses transported in Australia and management practices reported may not be compliant with current recommendations for transportation.

Respiratory Support for Pharmacologically Induced Hypoxia in Neonatal Calves.

Practical methods to provide respiratory support to bovine neonates in a field setting are poorly characterised. This study evaluated the response of healthy neonatal calves with pharmacologically induced respiratory suppression to nasal oxygen insufflation and to continuous positive airway pressure (CPAP) delivered via an off-the-shelf device. Ten calves were randomised to receive either nasal oxygen insufflation (Group 1, n = 5) or CPAP (Group 2, n = 5) as a first treatment after induction of respiratory depression by intravenous administration of xylazine, fentanyl, and diazepam. Calves received the alternate treatment after 10 minutes of breathing ambient air. Arterial blood gas samples were obtained prior to sedation, following sedation, following the first and second treatment, and after breathing ambient air before and after the second treatment. Oxygen insufflation significantly increased arterial oxygen partial pressure (PaO2) but was also associated with significant hypercapnia. When used as the first treatment, CPAP was associated with significantly decreased arterial partial pressure of carbon dioxide but did not increase PaO2. These results suggest that the use of CPAP may represent a practical method for correction of hypercapnia associated with inadequate ventilation in a field setting, and further research is required to characterise the use of CPAP with increased inspired oxygen concentrations.

Fibrinous pericarditis and pericardial effusion in three neonatal foals.

CASE SERIES: Three foals, aged between 5 and 10 days, were presented for assessment of lethargy, abdominal pain and joint effusion. Fibrinous pericarditis and pericardial effusion (PE) were recognised in each foal and considered as sequelae to systemic inflammatory response syndrome (SIRS) and suspected or confirmed septicaemia. CLINICAL COURSE AND OUTCOME: Diagnosis of pericarditis was made in two foals by echocardiographic examination and analysis of pericardial fluid, and during postmortem examination of the third foal. In both of the foals that underwent pericardiocentesis, PE was an exudate, no bacteria were identified on cytological analysis and bacterial culture was negative. Despite apparent response to treatment, two foals died 2 and 3 weeks, respectively, after discharge from hospital. One foal was euthanased during hospitalisation. CONCLUSION AND CLINICAL RELEVANCE: This report highlights the need to consider the development of pericarditis and PE in foals with SIRS and signs of cardiorespiratory dysfunction, and the requirement for protracted follow-up to monitor for clinical resolution.

Pharmacokinetics and safety of oral administration of meloxicam to foals.

BACKGROUND: The pharmacokinetics, efficacy, and safety of meloxicam have been evaluated in adult horses, but not foals. Physiologic differences between neonates and adults might alter drug pharmacokinetics and therapeutic index. HYPOTHESES: The pharmacokinetics of meloxicam will be different in foals compared with adult horses, and foals could be at increased risk for adverse drug effects. ANIMALS: Twenty lightbreed foals less than 6 weeks of age at commencement of the study. METHODS: Single and repeated oral dose pharmacokinetics were determined for meloxicam (0.6 mg/kg) in 10 foals. The safety of the drug was further evaluated in a 2nd group of 10 foals in a randomized blinded prospective study. RESULTS: Plasma concentrations after a single oral dose of meloxicam (0.6 mg/kg) and time to maximum plasma concentration were similar to adult horses. However, drug clearance was much more rapid in foals (elimination half-life 2.48 ± 0.25 hours). Administration of 0.6 mg/kg every 12 hours was well tolerated by foals for up to 3 weeks, with no evidence of drug accumulation in plasma. Adverse effects observed in adult horses at higher dose rates were not observed in foals given 1.8 mg/kg twice daily for 7 days. CONCLUSIONS AND CLINICAL IMPORTANCE: Meloxicam at an oral dose rate of 0.6 mg/kg every 12 hours provided plasma concentrations likely to be therapeutic. In contrast to findings for other NSAIDs, foals appeared more resilient to the adverse effects of this drug than was observed in adult horses.

Effects of meloxicam and phenylbutazone on equine gastric mucosal permeability.

BACKGROUND: Newer NSAIDs that more selectively target the induced isoform of the cyclooxygenase enzyme (COX2) activity might reduce adverse effects while preserving therapeutic benefits of these drugs. OBJECTIVES: To compare the effect of oral administration of multiple dose rates of meloxicam and phenylbutazone (PBZ) on gastric mucosal integrity in horses. ANIMALS: Twenty-five light breed horses. METHODS: In vivo toxicity study. Horses were randomly assigned to 5 treatment groups, receiving placebo, PBZ (4.4 mg/kg PO q12h day 1, 2.2 mg/kg PO q12h for 4 days, 2.2 mg/kg PO q24h for 9 days), or 3 dose rates of meloxicam (0.6 mg/kg q24h, 1.8 mg/kg q24h, 3.0 mg/kg q24h) for 14 days. Sucrose permeability testing was performed on Day 0 (before treatment) and on Day 13. All personnel involved with data collection or analysis were blinded to treatment. RESULTS: Administration of PBZ at the above dose rate significantly increased gastric permeability to sucrose, evidenced by increased peak serum sucrose concentrations (280-1,580 pg/µL, P = .001) after treatment. Similar changes were not evident after administration of meloxicam at any dose rate tested, or in control horses (P > .05). Treatment was not associated with significant differences in ulceration of the squamous or glandular mucosa. Peak sucrose concentrations were not correlated with serum total protein or albumin concentrations (R(2) = -0.07, P = .61, R(2) = -0.08, P = .58, respectively). CONCLUSION AND CLINICAL IMPORTANCE: These results suggest that PBZ was associated with greater compromise to gastric mucosal integrity than meloxicam.

Pharmacokinetics and safety of single and multiple oral doses of meloxicam in adult horses.

BACKGROUND: Safety of meloxicam, a potent NSAID with selective COX-2 inhibition, has not been evaluated in horses. OBJECTIVES: To evaluate pharmacokinetics and safety of single and repeated oral doses of meloxicam in adult horses. ANIMALS: Forty-nine healthy, university-owned adult lightbreed horses. METHODS: Study conducted in 2 parts. Part I addressed pharmacokinetics of single oral dose meloxicam (0.6 mg/kg) in 16 horses. Part II, 33 horses were randomly assigned to 5 treatment groups to assess prolonged administration (0.6 mg/kg PO q24h for 6 weeks, n = 7) or higher doses (1.8 mg/kg, n = 7, or 3.0 mg/kg PO q24h, n = 7) of meloxicam for 2 weeks, compared with control horses (placebo, n = 7, or phenylbutazone, 4.4 mg/kg q12h on day 1, 2.2 mg/kg q12h for 4 days, then 2.2 mg/kg q24h for 9 days, n = 5). RESULTS: Maximum plasma concentration following a single oral dose of meloxicam was 915.1 ± 116.9 ng/mL and elimination half-life 10.2 ± 3.0 hours. Meloxicam (0.6 mg/kg, q24h, PO for 6 weeks) yielded plasma concentrations between 100 and 1000 ng/mL and was well tolerated by healthy adult horses. Administration of 3-5 times the recommended dose of meloxicam was associated with decreased total serum protein and albumin concentrations, gastrointestinal damage, renal damage, or bone marrow dyscrasia. PBZ administration was associated with the development right dorsal colitis, gastric ulceration, and protein losing enteropathy in 2 horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Administration meloxicam at 0.6 mg/kg q24h was well tolerated for 6 weeks, without drug accumulation in plasma. Higher doses were associated with dose-dependent adverse effects typical of class of drugs.