Untreated Horses Research Articles

Dental Correction Does Not Alter Postprandial Nutrient Concentrations in Healthy Mares

Irregular wear patterns are theorized to cause poor feed digestion and weight loss in the horse. The objective of this study was to test the hypothesis that dental correction would increase postprandial nutrient concentrations and reduce fecal particle size (FPS) in clinically healthy mares. The study was conducted in 16 mares of mature age (4–17) who had not received dental care in the previous year. A diet consisting of ad libitum Coastal Bermudagrass hay and 1.36 kg of a pelleted feed was fed daily prior to and during the study. Eight mares received dental work and eight served as untreated controls. While the consumption of a concentrate meal increased plasma concentrations of glucose and amino acids at 90 minutes postfeeding (P < .001), dental correction did not have an influence on plasma nutrient concentrations (P > .1). On day 56, untreated control horses had a larger percent of large FPS than horses having received dental correction (14.7 ± 0.1 vs. 12.5 ± 0.1; P = .028). Dental correction may improve mechanical digestion of feed, but this does not translate to altered postprandial plasma nutrient concentrations following the consumption of a concentrate meal.

Effect of Sugar Beet Pulp on the Composition and Predicted Function of Equine Fecal Microbiota.

The purpose of this study is to determine the effect of the partial replacement of dietary hay with sugar beet pulp (SBP) on the composition and predicted function of the fecal microbiota of healthy adult horses. Fecal samples were collected daily for 12 days from six adult horses after removal from pasture, including a five-day acclimation period, and a seven-day period following the introduction of SBP into their diet, and compared to six untreated horses over a comparable period. Fecal DNA was subjected to 16S rRNA amplicon sequencing and a longitudinal analysis was performed comparing the composition and predicted function. While no significant treatment-associated changes in the richness, alpha diversity, or beta diversity were detected, random forest regression identified several high-importance taxonomic features associated with change over time in horses receiving SBP. A similar analysis of the predicted functional pathways identified several high-importance pathways, including those involved in the production of L-methionine and butyrate. These data suggest that feeding SBP to healthy adult horses acutely increases the relative abundance of several Gram-positive taxa, including Cellulosilyticum sp., Moryella sp., and Weissella sp., and mitigates the predicted functional changes associated with removal from pasture. Large-scale studies are needed to assess the protective effect of SBP on the incidence of the gastrointestinal conditions of horses.

The Effect of Inhaled Ciclesonide Treatment on Systemic Markers of Immune Function in Horses

The use of dexamethasone to control equine asthma is a common and effective treatment. Although short-term systemic dexamethasone treatment has not been shown to induce systemic immunosuppression in the horse, the goal of this study was to determine whether inhaled ciclesonide, an FDA-approved drug for the treatment of equine asthma, exerts any systemic immunosuppressive effects when compared to dexamethasone-treated and untreated horses. Eighteen light, mixed breed horses, ranging in age from 3 to 8 years of age, were used for this study and randomly assigned to one of three treatment groups: (1) nontreated controls, (2) ciclesonide treatment, or (3) dexamethasone treatment. Blood was collected daily for steady-state messenger RNA (mRNA) analysis, as well as at Days 0, 5, 10, and 15 of treatment for in vitro stimulation with Concanavalin A (ConA). Messenger RNA relative quantities were determined using RT-qPCR for select genes. Two-way, repeated measures analysis of variance was used to analyze qPCR data and results considered significant at P < .05. There were significant decreases in the steady-state, whole-blood expression of granzyme B and interferon-γ due to dexamethasone treatment, when compared to the nontreated control group. Within ConA-stimulated samples, there remained a suppressive effect of dexamethasone treatment on granzyme B expression compared to nontreated control horses. Similar effects were not noted in the ciclesonide-treated horses. Significant effects of ciclesonide treatment on markers of immune function were not noted in this study, suggesting a low risk for immunosuppression with inhaled ciclesonide treatment.

Detection of boldenone in the urine of female horses-ex vivo formation versus administration.

Boldenone is an anabolic-androgenic steroid (AAS) that is prohibited in equine sports. However, in certain situations, it is endogenous, potentially formed by the microbes in urine. An approach to the differentiation based on the detection of the biomarkers Δ1-progesterone, 20(S)-hydroxy-Δ1-progesterone and 20(S)-hydroxyprogesterone was assessed, and their concentrations were monitored in the urine of untreated female horses (n = 291) alongside boldenone, boldienone, testosterone and androstenedione. Using an ultra-sensitive analytical method, boldenone (256 ± 236 pg/mL, n = 290) and the biomarkers (Δ1-progesterone up to 57.6pg/mL, n = 8; 20(S)-hydroxy-Δ1-progesterone 85.3 ± 181 pg/mL, n = 130; 20(S)-hydroxyprogesterone 43.5 ± 92.1pg/mL, n = 158) were detected at low concentrations. The ex vivo production of Δ1-steroids was artificially induced following the storage of urine samples at room temperature for 7days in order to assess the concentrations and ratios of the monitored steroids. The administration of inappropriately stored feed source also resulted in an increase in 20(S)-hydroxy-Δ1-progesterone concentrations and the biomarker ratios. Using the results from different datasets, an approach to differentiation was developed. In situations where the presence of boldenone exceeds a proposed action limit of 5ng/mL, the presence of the biomarkers would be investigated. If Δ1-progesterone is above 50 pg/mL or if 20(S)-hydroxy-Δ1-progesterone is above 100 pg/mL with the ratio of 20(S)-hydroxy-Δ1-progesterone:20(S)-hydroxyprogesterone greater than 5:1, then this would indicate ex vivo transformation or consumption of altered feed rather than steroid administration. There remains a (small) possibility of a false negative result, but the model increases confidence that adverse analytical findings reported in female horses are caused by AAS administrations.

Performance assessment of an equine metabolomics model for screening a range of anabolic agents.

Despite their ban, Anabolic Androgenic Steroids (AAS) are considered as the most important threat for equine doping purposes. In the context of controlling such practices in horse racing, metabolomics has emerged as a promising alternative strategy to study the effect of a substance on metabolism and to discover new relevant biomarkers of effect. Based on the monitoring of 4 metabolomics derived candidate biomarkers in urine, a prediction model to screen for testosterone esters abuse was previously developed. The present work focuses on assessing the robustness of the associated method and define its scope of application. Several hundred urine samples were selected from 14 different horses of ethically approved administration studies involving various doping agents' (AAS, SARMS, β-agonists, SAID, NSAID) (328 urine samples). In addition, 553 urine samples from untreated horses of doping control population were included in the study. Samples were characterized with the previously described LC-HRMS/MS method, with the objective of assessing both its biological and analytical robustness. The study concluded that the measurement of the 4 biomarkers involved in the model was fit for purpose. Further, the classification model confirmed its effectiveness in screening for testosterone esters use; and it demonstrated its ability to screen for the misuse of other anabolic agents, allowing the development of a global screening tool dedicated to this class of substances. Finally, the results were compared to a direct screening method targeting anabolic agents demonstrating complementary performances of traditional and omics approaches in the screening of anabolic agents in horses.

Effects of oral treatment with chondroitin sulfate and glucosamine in an experimental model of metacarpophalangeal osteoarthritis in horses

BackgroundCombined chondroitin sulfate (CS) and glucosamine (GlcN) has been widely used in oral formulations to prevent and treat osteoarthritis. CS is effective for controlling pain in osteoarthritic patients, whereas GlcN can stimulate glycosaminoglycan synthesis, thus reducing extracellular matrix degradation. Although several studies have been published on this topic, the effectiveness of treatment with oral CS and GlcN remains uncertain. The objective of this study was to analyze the progression of experimentally induced osteoarthritis in horses and verify the effectiveness of an oral compound based on CS and GlcN to treat and/or modulate this disease. The study analyzed the metacarpophalangeal joint of the left thoracic limb of 16 horses divided into two groups, with eight horses treated with CS and GlcN in the treated group (GT) and eight untreated horses in the control group (GC). Chondral lesions were induced through arthroscopy, which was defined as time-point zero (T0). Physical, ultrasonographic, and radiographic examinations and synovial fluid biomarkers measurements were performed on days 0, 30, 60, 90, and 120. At the end of the experiment (T4), arthroscopy was performed again to macroscopically evaluate the joints and collect material for microscopic analysis.ResultsSignificant differences were observed between groups in some evaluated parameters, such as visual lameness assessment, synovial concentrations of prostaglandin E2, and ultrasound examination. However, the GT still presented slightly improved results for joint flexion angle, analysis of lameness using sensors, and histopathological analysis of chondral repair tissue, however, without the statistical significance (p>0.05).ConclusionsThe treatment was considered effective in the clinical modulation of experimental osteoarthritis, with improvement of some parameters in the GT. However, this type of treatment may not be entirely effective to change the catabolic process in articular cartilage and the progressive induced chondral damage.

Parasite dynamics in untreated horses through one calendar year

BackgroundHorses are host to a plethora of parasites. Knowledge of the seasonality of parasite egg shedding and transmission is important for constructing parasite control programs. However, studies describing these patterns are sparse, and have largely been conducted only in the United Kingdom. This study evaluated strongylid egg shedding patterns and transmission dynamics of Strongylus vulgaris in naturally infected and untreated mares and foals through one calendar year in Kentucky, USA. The study also investigated the existence of a peri-parturient rise (PPR) in strongylid egg counts in foaling mares and collected information about Strongyloides westeri and Parascaris spp. in the foals.MethodsThis study was conducted from January to December 2018. A herd of 18 mares, one stallion, and 14 foals born in 2018 were followed throughout the year. Sera and feces were collected biweekly from all horses, and worm burdens enumerated in 13 foals at necropsy. An S. vulgaris ELISA antibody test was run on all serum samples. Fecal egg counts were determined for all horses, and coproculture and qPCR assay were employed to test for the presence of S. vulgaris in the mature horses. Data were analyzed using the proc glimmix procedure in the SAS 9.4 software program.ResultsWe found a general lack of seasonality in strongylid egg shedding throughout the year among the mature horses, and no PPR was demonstrated. Shedding of S. vulgaris eggs displayed a higher abundance during the spring, but findings were variable and not statistically significant. Anti-S. vulgaris antibody concentrations did not display significant fluctuations in the mature horses, but evidence of passive transfer of antibodies to the foals was demonstrated, and foals assumed their own production of antibodies starting at approximately 20 weeks of age. Overall, colts shed higher numbers of strongylid, ascarid, and S. westeri eggs than fillies.ConclusionsThis study demonstrated a lack of seasonality in strongylid egg shedding for the study population, which is in stark contrast to previous studies conducted elsewhere. This strongly suggests that more studies should be done investigating these patterns under different climatic conditions.Graphical

Effects of branched-chain amino acids on immune status of young racing horses.

High-intensity exercise and competition are associated with depressed immune function. Young horses, which participate in high-intensity exercise and competitions, are at increased risk for the development of infectious disease due to depression of immune function. The effects of branched-chain amino acid (BCAA) supplementation on the immune status of young racing horses were evaluated, determining whether BCAA might help to avoid or reduce immune suppression during exercise and competitions. Twenty horses (10 male and 10 female) were treated with BCAA supplementation; another twenty untreated horses (10 male and 10 female) constituted control group. Peripheral blood was collected from each animal and evaluated for lymphocyte subsets, phagocytosis analysis of monocytes and granulocytes, lymphocyte proliferative response, and expression of cytokine-encoding messenger ribonucleic acids (mRNAs). The numbers of CD4+, CD8+, and major histocompatibility complex (MHC) class II+ cells in females of the treated group were significantly higher than those in females of the control group. The lymphocyte proliferative response in female of the treated group also was significantly higher than that in females of the control group. In addition, expression of mRNAs encoding interleukin-1β (IL-1β) and interferon-γ (IFN-γ) in females of the treated group was significantly higher than that in females of the control group. There were no significant differences between males of the treated and control groups. The results of this study indicated the positive effects of BCAA supplementation in counteracting immunosuppression in young female racing horses during and following high-intensity exercise.

Colonic Health in Hospitalized Horses Treated with Non-Steroidal Anti-Inflammatory Drugs – A Preliminary Study

Non-steroidal anti-inflammatory drugs (NSAIDs) can cause right dorsal colitis, but longitudinal clinical studies are lacking. This study investigates whether NSAID treated horses develop right dorsal colonic pathology in a clinical setting. Non-gastrointestinal hospitalized horses treated with NSAIDs >4 days, and untreated hospital-owned teaching horses and non-gastrointestinal client-owned hospitalized horses were included. All horses were monitored over time with clinical examinations (focusing on presence of colic, depression, reduced appetite, unstructured feces), ultrasonographic intestinal wall measurements, fecal occult blood tests (semi-quantitative results), and blood analysis (total protein and albumin concentrations, white blood cell and neutrophil counts). Outcomes were recorded as “ultrasonographically thickened right dorsal colon (RDC) walls”, “colitis” and “right dorsal colitis”. Findings over time were compared to baseline values and to control horses. Seventeen NSAID treated horses and 5 controls were included. NSAID treated horses developed thickened RDC walls (4/9), and subclinical and mild colitis (9/11) and right dorsal colitis (4/10), whereas all control horses remained healthy. The first changes were identified on treatment day 2. RDC walls of treated horses were significantly thicker compared to their own baseline values and compared to control horses. In conclusion, presumptive colon pathology was identified with a high incidence, starting early in the course of treatment, but with low severity. Appropriate monitoring should be advised throughout NSAID treatment. Additional research for noninvasive diagnostic tests for colon pathology is required.

Assessment of clinical and microbiota responses to fecal microbial transplantation in adult horses with diarrhea.

Background and aimsFecal microbial transplantation (FMT) is empirically implemented in horses with colitis to facilitate resolution of diarrhea. The purpose of this study was to assess FMT as a clinical treatment and modulator of fecal microbiota in hospitalized horses with colitis.MethodsA total of 22 horses with moderate to severe diarrhea, consistent with a diagnosis of colitis, were enrolled at two referral hospitals (L1: n = 12; L2: n = 10). FMT was performed in all 12 patients on 3 consecutive days at L1, while treatment at L2 consisted of standard care without FMT. Manure was collected once daily for 4 days from the rectum in all colitis horses, prior to FMT for horses at L1, and from each manure sample used for FMT. Fecal samples from 10 clinically healthy control horses housed at L2, and 30 healthy horses located at 5 barns in regional proximity to L1 were also obtained to characterize the regional healthy equine microbiome. All fecal microbiota were analyzed using 16S amplicon sequencing.Results and conclusionsAs expected, healthy horses at both locations showed a greater α-diversity and lower β-diversity compared to horses with colitis. The fecal microbiome of healthy horses clustered by location, with L1 horses showing a higher prevalence of Kiritimatiellaeota. Improved manure consistency (lower diarrhea score) was associated with a greater α-diversity in horses with colitis at both locations (L1: r = -0.385, P = 0.006; L2: r = -0.479, P = 0.002). Fecal transplant recipients demonstrated a greater overall reduction in diarrhea score (median: 4±3 grades), compared to untreated horses (median: 1.5±3 grades, P = 0.021), with a higher incidence in day-over-day improvement in diarrhea (22/36 (61%) vs. 10/28 (36%) instances, P = 0.011). When comparing microbiota of diseased horses at study conclusion to that of healthy controls, FMT-treated horses showed a lower mean UniFrac distance (0.53±0.27) than untreated horses (0.62±0.26, P<0.001), indicating greater normalization of the microbiome in FMT-treated patients.

Precision and spatial variation of cyathostomin mucosal larval counts

Cyathostomins are pervasive parasites of equids across the world. Larval stages encyst in the mucosa of the cecum, ventral and dorsal colon and can induce an inflammatory response leading to larval cyathostominosis, a life-threatening generalized typhlocolitis. Mucosal digestion is the only gold standard procedure for identifying and quantifying all larval stages. There is a lack of standardization of this technique and several aspects are ambiguous, such as precision of the method and the possibility of spatial variation of mucosal larval counts. The aim of this study was to estimate precision for enumeration of early third stage larvae (EL3) and late third stage/fourth stage (LL3/L4) larvae and investigate spatial variation of encysted counts within large intestinal organs. Six naturally infected and untreated horses aged 2–5 years were euthanized as part of an anthelmintic efficacy study, and the cecum (Cec), ventral colon (VC) and dorsal colon (DC) were collected. Each organ was rinsed, weighed, and visually separated into 3 equally sized sections. Two 5% tissue samples were collected from each section, a total of six replicates per organ. The mucosae were digested, and 2% examined under the microscope for presence of EL3 and LL3/L4 stage larvae. Overall, 59 % of the harvested larvae were EL3s, and 41 % were LL3/L4s. The ventral colons represented 45 % of the total organ weight, and contributed 37 and 41 % of the EL3s and LL3/L4s harvested, respectively. The Cec, representing only 27 % of the weight contributed 23 % of EL3s and 47 % of LL3/L4s. The DC represented 28 % of the total organ weight, and 28 % and 12 % of the total EL3s and LL3/L4s, respectively. Coefficients of variation varied from 33 to 183 % for EL3 counts and 38–245% for LL3/L4 counts. There were no statistically significant associations between EL3 counts and either organ or location. For LL3/L4 counts there were no statistically significant differences between the three locations within organs (p = 0.1166), but the DC had significantly lower counts than the other two organs (p < 0.0001). Increasing the number of mucosal replicates from each organ improved estimation, but required a considerably increased workload. In conclusion, mucosal larval cyathostomin counts are highly variable, complicating their use for treatment efficacy estimation.

Preliminary study on the effects of pergolide on left ventricular function in the horses with pituitary pars intermedia dysfunction.

BackgroundPituitary pars intermedia dysfunction (PPID), a neurodegenerative disease leading to reduced dopamine production, is a common disease in aged horses. The treatment is based on administration of the dopamine agonist pergolide. This drug has been related to valvular fibrosis in humans, but the cardiovascular effect of this drug has not yet been investigated in horses.ObjectivesTo determine whether pergolide induces valvular disease in horses or affects the cardiac function.MethodsStandard, tissue Doppler (TDE) and two-dimensional speckle tracking (STE) echocardiography were performed in horses with diagnosed PPID based on adrenocorticotropic hormone dosage. Measurements taken in horses treated with pergolide were compared with those from untreated horses with nonparametric t-tests. Furthermore, measurements from follow-up examinations performed at least three months after the initial exam were compared with a Wilcoxon signed rank test for repeated measurements in each group.ResultsTwenty-three horses were included. None of the 12 horses under treatment developed valvular regurgitation. Furthermore, no differences in the measurements of the left ventricular systolic or diastolic function could be seen between the group of horses with treatment and those without treatment. Measurements taken in the follow-up exam did not differ compared to those taken in the initial exam in both groups.ConclusionsNo changes of the left ventricular function assessed by TDE and STE could be shown in a small population of horses with confirmed PPID. Treatment with pergolide did not affect the ventricular function nor induce valvular disease.

Intrasynovial triamcinolone treatment is not associated with incidence of acute laminitis.

Intrasynovial corticosteroid injections are commonly used in the treatment of equine orthopaedic disease, but corticosteroid administration is widely considered a risk factor for the development of laminitis. Despite a list of putative mechanisms and a number of case reports of steroid-induced laminitis, no case-control or cohort studies investigating the association between use of intrasynovial corticosteroids and acute laminitis have been published. To quantify the risk of laminitis posed by intrasynovial triamcinolone acetonide (TA) administration in a mixed population of horses. Retrospective observational cohort study. Clinical records of horses registered with one large UK equine practice were reviewed retrospectively to identify all horses receiving intrasynovial TA treatment between 1 January 2007 and 31 December 2017. A total of 1510 horses were selected and records investigated for incidence of laminitis over a 4-month period following treatment. For each TA-treated horse, an untreated horse, individually matched by age, sex, date of treatment and client type, was selected from the clinical records. Untreated horses were then investigated for laminitis over the same 4-month period. Data were analysed in a 2×2 contingency table using Fisher's exact test. A total of 489 horses were lost to follow-up and 55 horses were excluded, leaving 966 treated and matched, untreated horses. The incidence of laminitis over the 4-month study period in both groups was identical: 3/966 horses (0.31%) (95% C.I. [0.08%, 0.91%]), equivalent to 0.93 cases per 100 horses per year (P>.9). Retrospective study; large proportion (489/1510) of horses lost to follow-up; large proportion of study population were racehorses; selection method resulted in disproportionate selection of horses born before 2013; similar incidence between groups may reflect existing risk-based selection by clinicians. intrasynovial triamcinolone acetonide administration does not increase the risk of laminitis in this study population.

Restoring pars intermedia dopamine concentrations and tyrosine hydroxylase expression levels with pergolide: evidence from horses with pituitary pars intermedia dysfunction

BackgroundPituitary pars intermedia dysfunction (PPID) develops slowly in aged horses as degeneration of hypothalamic dopaminergic neurons leads to proliferation of pars intermedia (PI) melanotropes through hyperplasia and adenoma formation. Dopamine (DA) concentrations and tyrosine hydroxylase (TH) immunoreactivity are markedly reduced in PI tissue of PPID-affected equids and treatment with the DA receptor agonist pergolide results in notable clinical improvement. Thus, we hypothesized that pergolide treatment of PPID-affected horses would result in greater DA and TH levels in PI tissue collected from PPID-affected horses versus untreated PPID-affected horses.To test this hypothesis, pituitary glands were removed from 18 horses: four untreated PPID-affected horses, four aged and four young horses without signs of PPID, and six PPID-affected horses that had been treated with pergolide at 2 µg/kg orally once daily for 6 months. DA concentrations and TH expression levels in PI tissues were determined by high performance liquid chromatography with electrochemical detection and Western blot analyses, respectively. ResultsDA and TH levels were lowest in PI collected from untreated PPID-affected horses while levels in the pergolide treated horses were similar to those of aged horses without signs of PPID.ConclusionsThese findings provide evidence of restoration of DA and TH levels following treatment with pergolide. Equine PPID is a potential animal model of dopaminergic neurodegeneration, which could provide insight into human neurodegenerative diseases.

Sample Entropy Analysis of Horses with and without Lameness at Trot before and after Sedation

The horses were trotted in a straight line, and the acceleration data were recorded from the movement of the horse’s head. Inertial sensors were used to collect the information. The sample entropy was used to characterize the dynamics of horse gait. The gait of sound and lame horses was compared, and the sound horses had smaller values of the sample entropy. The effects of sedative detomidine on the gait of lame horses were also examined. The values of sample entropy for sedated horses were smaller than the values of the sample entropy for untreated horses. The sample entropy can provide important information about the dynamics of the equine gait.

The effect of different antimicrobial treatment regimens on the faecal shedding of ESBL-producing Escherichia coli in horses

Fourth-generation cephalosporins can select for extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in horses, but it is unknown to what extent this occurs compared to penicillin/gentamicin combination treatment. The objective was to evaluate the effect of different antimicrobial treatments on faecal shedding and diversity of ESBL-producing Escherichia coli (ESBL-EC) in horses.Upon hospital admission, 86 horses in need of antimicrobial treatment or prophylaxis were randomly allocated to receive penicillin and gentamicin (PG) or cefquinome (CEF). Untreated horses were included as controls (NOAMD, n = 33). Faecal samples from admission (T1), 3 days after admission (T2), and faecal swabs 28 days after discharge (T3) were cultured selectively. Differences in prevalence (T1, T2, T3) and counts (T1, T2) of ESBL-EC between groups and over time were analysed. On a subset of ESBL-EC isolates, antimicrobial susceptibility testing (n = 45) and whole-genome sequencing followed by SNP-analysis (n = 46) were performed.The prevalence of ESBL-EC at T1 was 12 % with no significant difference between groups. In all groups, significantly higher carriage rates were observed at T2 and T3 compared to T1. Carriage and counts of ESBL-EC at T2 were significantly higher in treated compared to untreated horses. There was no significant difference between PG and CEF at any time points. Despite a large genetic diversity, indistinguishable ESBL clones were observed in different horses over time.In conclusion, antimicrobial treatment and hospitalization increased prevalence and counts of ESBL-EC, and transmission of ESBL-EC in the hospital was suspected. These findings highlight the importance of antimicrobial stewardship and infection control practices in equine medicine.

MRI Features of Fetlock and Pastern Regions in 30 Chronically, Un-Treated Lame Draft Horses Confirmed by Postmortem Examination

Lameness from fetlock and pastern regions is a big challenge to most equine practitioners and produces a detrimental effect on horses' activity and on owners' finances. Nuclear scintigraphy, radiography and ultrasonography are not conclusive when assessing of fetlock and pastern lameness. This study describes the magnetic resonance imaging (MRI) features in 30 draft horses with chronic, un-treated lameness attributable to fetlock and pastern regions as well as confirms these features by postmortem examination. Thirty-three cadaver limbs were collected after euthanasia, imaged by MR and lastly examined grossly. Seventeen lesions were recorded and described using MRI. MRI revealed injuries of both soft and osseous tissues in 24 horses (80%), soft tissue injuries in five horses (16.7%) and bone and cartilage injuries in one horse (3.3%). All horses had multiple MRI abnormalities. The most frequent MR lesions were digital tenosynovitis (n=13), straight sesamoidean desmitis (n=10), osteosclerosis in the distal part of third metacarpal bone (MCIII) or first phalanx (PI, n=10), adhesions between straight sesamoidean ligament (SSL) and deep digital flexor tendon (DDFT, n=9), oblique sesamoidean desmitis (n=7), cartilage erosions of fetlock or pastern joints (n=7), adhesions between proximal digital annular ligament and DDFT (n=6), DDFTendinitis at pre-navicular part (n=6), proximal digital annular desmitis (n=5), subchondral bone cyst of PI (n=3), and cyst like lesions in PI and PII (n=2). In conclusion, MRI played a pivotal role in comprehensive evaluation of fetlock and pastern regions and it is highly recommended for examination of all structures of fetlock and/or pastern regions in chronically lame draft horses.

Race performance following epiglottic entrapment surgery in Thoroughbred yearlings.

Epiglottic entrapment can occur in yearling Thoroughbreds (TB); however, race performance following surgical correction is unknown. To determine the race performance of horses treated surgically for epiglottic entrapment as yearlings as compared to an untreated cohort. A second objective was to identify risk factors for treated horses not racing post-operatively. Retrospective cohort and case-control studies. Medical (1989-2014) and race records of 66 treated TB racehorses were reviewed. Observed abnormalities on pre- and post-operative endoscopic images and surgical method were recorded. Race records (EquineLine) were recorded. Racing performance of treated yearling TBs and two of their maternal half-siblings, which were used as the untreated cohort, was evaluated in a cohort study. A case-control study was used to investigate risk factors for not racing post-operatively among treated horses. Quarterly starts and earnings were compared to an untreated cohort. Survival analysis was used to assess career longevity. Rates of racing and earnings were compared between groups using Poisson and negative binomial regression respectively. Associations between clinical variables and not racing post-surgery were evaluated using logistic regression. Sixty-six treated horses were identified, 65 of which had at least one half-sibling. Proportions of horses that raced were similar for treated and maternal cohorts (70.0 vs. 70.8%, P=0.9). Treated horses performed similarly to untreated horses. In treated horses, epiglottic entrapment with abnormal right arytenoid movement was associated with never racing (OR 15.40, 95% CI 1.64-144.23, P=0.02). More females were affected by epiglottic entrapment than males (47/66 vs. 19/66 respectively, P<0.001). The retrospective design over a prolonged period of time with cases obtained from a single hospital population. Low case numbers likely influenced the outcome of the multivariable analysis. Thoroughbred racehorses treated in their yearling year for epiglottic entrapment had no differences in performance variables compared to their untreated cohort. Epiglottic entrapment with abnormal right arytenoid movement might decrease odds of racing post-operatively.

What we know regarding the use of bisphosphonates in horses

Currently two bisphosphonates (BPs) are licensed for use in horses. Both tiludronate (TIL) and clodronate (CLO) are labelled specifically for the treatment of navicular disease, but are administered frequently for other suspected causes of lameness. Recommended administration routes are not always used, resulting in the risk of potential toxicities or increased patient morbidity. Numerous reports exist describing subjective improvements in subjective lameness following the administration of TIL or CLO, but little objective data exists to confirm this, or even reveal the effects these drugs have on the equine athlete. Our group has investigated the influence of TIL and CLO on pelvic biopsies from horses, before and 60 days after drug administration. MicroCT and histomorphometry were performed on all samples to evaluate changes to bone cells and structure, following a single dose of TIL (1mg/kg) or CLO (1.8mg/kg). Sixty days was chosen as the second biopsy date based on the clinical improvement observed in lameness studies reported in the literature. Biopsies were collected from a total of 19 horses (5 each for either TIL or CLO and 9 controls) at day 0 (pretreatment) and subsequently at day 60. No biologically significant histomorphometric or microCT differences were revealed in the bone structure, cells, or remodeling kinetics between the treated or control horses or between Day 0 biopsies (internal controls). This may have been related to study design and sampling times, or may reflect the relatively low potency of TIL and CLO as inhibitors of osteoclastic activity in the horse. The CLO group and their control horses also had the original biopsy site biopsied again at day 60, to investigate the effect on bone healing. Again, no changes were observed between the treated and untreated horses. TIL has been shown to have negative effects on chondrocytes, in horses, when administered at higher levels than those achieved following IV administration. This was investigated in response to veterinarians giving TIL via intraarticular injection or intravenous regional limb perfusions. The effects of high levels of CLO on chondrocytes have not been investigated to date, but the authors have completed a pharmacokinetic study which revealed plasma, synovial and urinary levels of CLO subsequent to administration of a single dose of CLO, at the appropriate dose. Renal injury is an acknowledged potential complication in healthy horses following administration of BPs. In the horses we investigated after administration of CLO, no alterations in serum BUN or creatinine or urine protein:creatinine ratios were observed. This information will help direct future studies into the safety and viability of CLO and its use in horses. With the lack of response seen in normal equine bone using clinically relevant doses, future investigations need to focus on examining the responses in a diseased state, or in a more refined model. Unfortunately, navicular disease is characterized by a wide variety of bone pathology and clinical signs, resulting in no standard model for investigation. For this reason, future investigation is necessary to identify the effects and potential benefits of these commonly used medications.Support or Funding InformationFunded by the LSU SVM EHSPThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Using quarterly earnings to assess racing performance in 66 thoroughbreds after transendoscopic laser surgery for treatment of epiglottic entrapment

To assess the outcome of transendoscopic laser surgery for the treatment of epiglottic entrapment (EE) and determine the influence of preoperative morphological characteristics on outcomes. Retrospective cohort study. Thoroughbred racehorses treated with transendoscopic laser surgery (n = 66) and untreated cohorts (n = 132). Medical, surgical, and race records of 66 horses treated with transendoscopic laser surgery were compared with untreated cohorts randomly selected from their last race presurgery. Postsurgery data were collated as number of starts and race winnings for each quarter after the date of surgery. Treated horses performed worse (P = .002) than their untreated cohorts in their last race presurgery. Although treated horses raced fewer times (P < .001) and earned less money (P < .001) in the first quarter after surgery compared with untreated horses, quarterly earnings or starts did not differ between groups after the first quarter. Among variables tested, subepiglottic membrane resection was the only prognostic factor; horses requiring this resection raced fewer times (P = .001) but without a significant difference in earnings. Horses treated for EE via transendoscopic laser surgery returned to a performance standard comparable to their untreated cohorts by the second quarter postsurgery. Horses with entrapments requiring resection raced fewer times postoperatively than the untreated cohorts. Treated horses can be expected to perform equivocally to that of untreated cohorts in all but the first quarter following surgery except in those cases where resection of the entrapping membranes is required.