High-speed treadmill videoendoscopic examination of the upper respiratory tract in the horse: the results of 291 clinical cases

Do tight nosebands have an effect on the upper airways of horses?

BACKGROUND/OBJECTIVES

The public perception relating to the welfare of horses involved with equestrian sports is associated with training methods used and the presentation of horses at events. In this context, very tight nosebands, which are intended to prevent the horse from opening its mouth, also attract a lot of attention. Various studies have evaluated the impact of tight nosebands on stress parameters, whereas the effect of tight nosebands on upper airway function is unknown. Therefore, the aim of the study was to use overground endoscopy to evaluate changes in pharyngeal and laryngeal function when a tight noseband is fitted. Moreover, the ridden horse pain ethogram (RHpE) was applied to investigate signs of discomfort (Dyson et al., 2018).

STUDY DESIGN

A randomized, blinded, and prospective study was performed.

METHODS

Sixteen warmblood horses consisting of twelve mares and four geldings with a mean age of 11.63 ± 3.53 years were ridden on 2 consecutive days with either loose or tight nosebands (two fingers or no space between bridge of the nose and noseband, respectively) and inserted endoscope in a random order. Videos were taken in a riding arena during a standardized exercise protocol involving beginner level tasks for 30 min in all gaits. For video analysis, freeze frames were prepared and analyzed at the beginning of the expiration phase. Pharyngeal diameter was measured using the pharynx-epiglottis ratio. Other findings (swallowing, pharyngeal collapse, soft palate movements, and secretion) were also evaluated. Moreover, the RHpE was applied. Descriptive statistics and generalized linear mixed effects models were used. Results with a p-value < 0.05 were considered statistically significant.

RESULTS

While the pharynx-epiglottis ratio did not change significantly in horses ridden with loose versus tight nosebands, there was an increase in mean grade and total counts of parameters assessed in the pharyngeal region, for example, grade of secretion (1.5 [±SD 0.89] vs. 3.13 [±SD 0.96]; p = 0.0001), axial deviation of the aryepiglottic folds (0.29 [±SD 0.73] vs. 1.33 [±SD 1.44]; p = 0.01), and pharyngeal collapse (0.69 [±SD 0.87] vs. 1.88 [±SD 1.54]; p = 0.005) in horses ridden with tight nosebands. There was no RHpE score above 8 indicating musculoskeletal pain, but the RHpE scores were significantly higher in horses ridden with tight nosebands (p < 0.001).

MAIN LIMITATIONS

Video quality was limited when horses showed large amounts of secretion. Another limitation was the small number of horses.

CONCLUSIONS

Results add to the evidence obtained in other studies that tight nosebands do not only cause adverse reactions based on the RHpE score such as head behind the vertical or intense staring but also contribute to changes in the pharyngeal region, such as increased secretion and collapse of pharyngeal structures. This may provide further support for future decisions regarding regulations on nosebands.

Upper airway endoscopy in exercising horses: Findings in 164 barrel racing horses with respiratory clinical signs and/or poor performance

Barrel racing involves sprinting through a cloverleaf pattern in under 20 s. The prevalence of upper airway obstructions (UAO) in barrel racers is unknown, thus a retrospective analysis of 164 client-owned horses referred for overground endoscopy (OGE) between 2014 and 2022 was performed. Referring complaints included respiratory noise, cough, epistaxis, behaviour (owner reported stress/anxiety, refusal to enter arena, excessive head shaking), and/or poor performance. Horses performed a standardized exercise test with low and high-speed components. Videoendoscopic recordings were systematically scored by one experienced clinician. Exercising abnormalities included palatal instability (PI), intermittent dorsal displacement of the soft palate (iDDSP), nasopharyngeal collapse (NPC), recurrent laryngeal neuropathy (RLN), ventro-medial luxation of the apex of the corniculate process of the arytenoid (VLAC), medial deviation of the aryepiglottic fold (MDAF), vocal fold collapse (VFC), and cricotracheal ligament collapse. Associations between co-existing UAOs, age and sex were examined (McNemar's test; logistic regression; P < 0.05). During exercise, 24/164 (15%) horses had no UAO. In the remaining 140 horses, 56% had two or more. NPC was observed in 68/140 (49%), PI in 59/140 (42%), iDDSP in 55/140 (39%), VFC in 38/140 (27%), RLN in 27/140 (19%), VLAC in 14/140 (10%), MDAF in 8/140 (6%) and cricotracheal ligament collapse in 8/140 (6%). Nasopharyngeal collapse and RLN were primarily Grade 3 and Grade B, respectively. Associations exist between several co-existing UAOs, but not age or sex. Abnormalities were more frequent at low-speed (55%) than high-speed (22%), highlighting the importance of OGEs at different exercise intensities. Multiple UAOs appear common in barrel racers with clinical presentations.

Medical causes of poor performance and their associations with fitness in Standardbred racehorses

BACKGROUND

Poor performance is a multifactorial syndrome of racehorses, commonly associated with subclinical disorders, which can be diagnosed by exercise testing.

OBJECTIVES

Describe the prevalence of medical causes of poor performance in Standardbreds unassociated with lameness, and evaluate their relationships with fitness variables measured by exercise treadmill test.

ANIMALS

Hospital population of 259 nonlame Standardbred trotters referred for poor performance.

METHODS

The horses' medical records were retrospectively reviewed. Horses underwent a diagnostic protocol including resting examination, plasma lactate concentration, treadmill test with continuous ECG and assessment of fitness variables, creatine kinase activity, treadmill endoscopy, postexercise tracheobronchoscopy, bronchoalveolar lavage (BAL), and gastroscopy. The prevalence of different disorders was evaluated, including cardiac arrhythmias, exertional myopathies, dynamic upper airway obstructions (DUAOs), exercise-induced pulmonary hemorrhage (EIPH), moderate equine asthma (MEA), and gastric ulcers (EGUS). The associations of these disorders with fitness variables were investigated individually and using multivariable models.

RESULTS

Moderate equine asthma and EGUS were the most common disorders, followed by EIPH, DUAOs, cardiac arrhythmias, and exertional myopathies. Hemosiderin score was positively correlated with BAL neutrophils, eosinophils, and mast cells; increased creatine kinase activity was associated with BAL neutrophilia, DUAOs, premature complexes, and squamous gastric disease. Treadmill velocity at a plasma lactate concentration of 4 mmol/L and at heart rate of 200 beats per minute was negatively affected by BAL neutrophilia, multiple DUAOs, exertional myopathies, and squamous gastric disease.

CONCLUSIONS

The multifactorial nature of poor performance was confirmed, with MEA, DUAOs, myopathies and EGUS representing the main diseases involved in fitness impairment.

Sustainability and the Thoroughbred Breeding and Racing Industries: An Enhanced One Welfare Perspective

As society debates the use of animals in sport, entertainment, and leisure, there is an increasing focus on the welfare, social, and ecological impacts of such activities on the animals, human participants, people close to them, and the physical environment. This article introduces the "Enhanced One Welfare Framework" to reveal significant costs and benefits associated with Thoroughbred breeding and racing globally. In addition, relative to calls to ban horseracing and similar activities as part of sustainability approaches that focus chiefly on animals, the "Enhanced One Welfare Framework" is better positioned politically to guide discussions that renegotiate the conditions under which horses are used for sport and the impact racing has on humans and the planet. In 2020, the International Federation of Horseracing Authorities issued its minimum horse welfare standards based on the Five Domains model, positioning lifelong horse welfare as "fundamentally important to the viability and sustainability of the industry". In this article, we critique the One Welfare framework's historic lack of focus on sport and enhance it by including sport, leisure, and entertainment and framing it within the Five Domains model. We offer a novel extension of the Five Domains model beyond animal welfare to consider human welfare and the physical environmental impacts of the sport, leisure, and entertainment industries and propose innovations that may help thoroughbred breeding and racing assure a sustainable future.

Upper and Lower Airways Evaluation and Its Relationship with Dynamic Upper Airway Obstruction in Racehorses

Dynamic upper airway obstructions (DUAO) are common in racehorses, but their pathogenetic mechanisms have not been completely clarified yet. Multiple studies suggest that alterations of the pharyngo-laryngeal region visible at resting endoscopy may be predictive of the onset of DUAO, and the development of DUAO may be associated with pharyngeal lymphoid hyperplasia (PLH), lower airway inflammation (LAI) and exercise-induced pulmonary hemorrhage (EIPH). The present study aims to investigate the possible relationship between the findings of a complete resting evaluation of the upper and lower airways and DUAO. In this retrospective study, 360 racehorses (Standardbreds and Thoroughbreds) referred for poor performance or abnormal respiratory noises were enrolled and underwent a diagnostic protocol including resting and high-speed treadmill endoscopy, cytological examination of the bronchoalveolar lavage fluid and radiographic assessment of the epiglottis length. In this population, epiglottis flaccidity was associated with dorsal displacement of the soft palate, while no relationship was detected between DUAO and epiglottis length. No associations were detected between DUAO and PLH, LAI or EIPH. In conclusion, it is likely that epiglottis plays a role in upper airway stability, while airways inflammation does not seem to be involved in the pathogenesis of DUAO.

Association between dynamic upper airway obstructions and fitness parameters in Standardbred racehorses during high-speed treadmill exercise

OBJECTIVE

To evaluate the association between the severity of dynamic upper airway obstruction (DUAO) and selected fitness parameters in Standardbred racehorses measured by treadmill test.

ANIMALS

191 Standardbred racehorses that underwent a standardized diagnostic protocol for poor performance evaluation between 2002 and 2021 at the Veterinary Teaching Hospital, University of Milan.

PROCEDURES

Horses underwent a diagnostic protocol including clinical examination, lameness evaluation, laboratory analyses, ECG, resting upper airway endoscopy, metabolic incremental treadmill test, high-speed treadmill endoscopy, postexercise tracheobronchoscopy, and bronchoalveolar lavage fluid cytology. On the basis of findings of the high-speed treadmill endoscopy, horses were divided into the following groups: no DUAO, mild DUAO (medial deviation of the aryepiglottic folds or epiglottic entrapment), severe DUAO (dorsal displacement of the soft palate, nasopharyngeal collapse, dynamic laryngeal collapse, or epiglottic retroversion), and multiple DUAOs (different forms of DUAO occurring concomitantly). Fitness parameters, measured by incremental treadmill test, included speed at a heart rate of 200 bpm (V200), speed and heart rate at a lactate concentration of 4 mmol/L (VLa4, HRLa4), peak lactate, maximum speed, maximum hematocrit, and minimum pH. Data were compared between groups by use of descriptive and statistical analyses.

RESULTS

Horses affected by severe or multiple DUAOs showed lower V200 and VLa4, compared to the no-DUAO group; horses with multiple DUAOs also had higher peak lactate concentrations compared to horses without DUAOs.

CLINICAL RELEVANCE

While mild forms of DUAO do not affect athletic capacity, severe forms of DUAO and multiple DUAOs may lead to reduced fitness in Standardbred racehorses by impairing aerobic capacity.

Influence of unilateral and bilateral vocal cordectomy on airflow across cadaveric equine larynges at different Rakestraw grades of arytenoid abduction

Objective

To assess the effect of vocal cordectomy on airflow across equine larynges at different Rakestraw grades of arytenoid abduction using a unidirectional airflow model.

Study design

Ex vivo, repeated measures.

Sample population

Twenty cadaveric equine larynges.

Methods

The right arytenoid cartilage was maximally abducted in all larynges. Each larynx was assigned a Rakestraw grade A or B, and the left arytenoid was abducted accordingly. Each larynx was tested under 3 conditions: intact, left vocal cordectomy (LVC), and bilateral vocal cordectomy (BVC). Translaryngeal pressure and airflow were measured, and digital video footage was obtained. Translaryngeal impedance (TLI) was calculated, and the arytenoid left‐to‐right quotient angle (LRQ) and rima glottis cross‐sectional area (CSA) were measured from standardized still images.

Results

Vocal cordectomy reduced TLI by 14.5% in LVC in comparison with intact larynges at Rakestraw grade B (P = .014). In Rakestraw grade A position, neither unilateral nor bilateral vocal cordectomy had any effect on TLI. Regardless of Rakestraw allocation, both LVC and BVC increased CSA in comparison with intact larynges (P < .005), with BVC larynges experiencing a greater effect than LVC (P < .0001).

Conclusion

Using a unilateral airflow model, LVC improved TLI in larynges where arytenoid position approximated Rakestraw grade B. However, when the arytenoid position approximated Rakestraw grade A, there was no effect on TLI following LVC or BVC.

Clinical significance

Surgeons considering a vocal cordectomy should take into account the degree of arytenoid abduction before performing the procedure, as it may not be warranted from a TLI point of view.

Evaluation of postsale endoscopy as a predictor of future racing performance in an Australian thoroughbred yearling population

Introduction

Upper airway endoscopy of thoroughbred (TB) yearlings is commonly used in an attempt to predict laryngeal function (LF) and its impact on future race performance. The aim of this study was to determine if different grading systems and laryngeal grades were correlated with future performance.

Materials and Methods

Postsale endoscopic recordings were obtained from an Australian TB yearling sale during a four‐year period from 2008 to 2011. Horses were included if they had a diagnostic postsale video endoscopic recording and raced within Australia. Recordings were graded using the Havemeyer system and subsequently recategorised according to the Lane scale and two condensed scales. Performance data were sourced from Racing Australia and comparisons were made between groups.

Results

A total of 1244 horses met the inclusion criteria. There were no significant differences in sex or sales price between groups. There were no significant differences in the number of starts or wins between groups for any grading system. For the condensed Havemeyer scale, horses with intermediate LF were separated into two groups. Significant differences in earnings were found between ‘normal’ and ‘abnormal’ (P = 0.02) and ‘intermediate‐low’ and ‘abnormal’ grades (P = 0.03). There were no significant differences between horses with ‘intermediate‐high’ and ‘abnormal’ grades (P = 0.40). No significant differences were found between the two intermediate grades (P = 0.60) or between horses with normal LF and either ‘intermediate‐low’ or ‘intermediate‐high’ grades (P = 0.99).

Discussion

Resting LF in Australian yearling TBs assessed using a condensed Havemeyer grading scale had some predictive value for future racing performance. This information should be considered when performing yearling endoscopic examinations.

The Reported Use of Tongue-Ties and Nosebands in Thoroughbred and Standardbred Horse Racing-A Pilot Study

Simple Summary

Tongue-ties (TTs) are commonly used in racing to restrain a horse’s tongue to aid a rider’s/driver’s control of the horse and optimise upper airway function. Nosebands (NBs) may also be employed for similar purposes. This article reports on a survey that asked people involved in Thoroughbred (TB) and Standardbred (SB) racing whether they used TTs and NBs and, if they did, the reasons for their use, the preferred design of device, the devices’ perceived effectiveness at achieving the respondents’ desired outcome(s), any complications due to their use and whether or not these complications altered their decision to use a particular type of TT or NB. A total of 112 participants involved with TB and SB racing answered TT questions. It revealed that respondents who used TTs believed them to be very or extremely effective at preventing the tongue from moving over the bit and improving upper airway function. Both physical and behavioural complications due to the use of a TT were reported. The likelihood of a respondent reporting a complication due to TT use increased with every minute of reported application and a nine-minute increment in the reported duration of application doubled the odds of a respondent reporting a behavioural complication. The findings of this study should be considered only as those of a pilot study and should be interpreted with caution due to the small number of responses.

Abstract

This article reports on the results of a survey of racehorse trainers (n = 112) outlining the reasons for tongue-tie (TT) and noseband (NB) use by Thoroughbred trainers (TBTs) (n = 72) and Standardbred trainers (SBTs) (n = 40). The study also investigated the reported effectiveness of TTs and possible complications arising from their use. Tongue-tie use was reported by 62.5% (n = 70) of racehorse trainers. The reasons for TT use varied between TBTs and SBTs. For TBTs, the most common reason for TT use was to prevent or reduce airway obstruction (72.3%, n = 34), followed closely by to prevent or reduce airway noise (55.3%, n = 16). Standardbred trainers assigned equal importance for TT use [to prevent or reduce airway obstruction (69.6%, n = 16) and to prevent the horse from moving its tongue over the bit (69.6%, n = 16)]. Tongue-ties were considered significantly less effective at improving performance than at reducing airway obstruction and preventing the tongue from moving over the bit (t = −2.700, p = 0.0007). For respondents who used both TTs and NBs, there was a mild to moderate positive association between the reasons for using TTs and NBs. Of the 70 TT-using respondents, 51.4% (n = 36) recorded having encountered either a physical or behavioural complication due to TT use, with redness/bruising of the tongue (20.0%, n = 14) being the most common physical complication reported. Duration of use influenced the risk of observing complications. The likelihood of a respondent reporting a behavioural complication due to TT use increased with every minute of reported application and a nine-minute increment in application period doubled the odds of a respondent reporting a complication. Tightness was a risk factor for physical complications: Checking TT tightness by noting the tongue as not moving was associated with increased reporting of physical complications (OR = 6.59; CI 1.1–67.5). This pilot study provides some insight into how and why TTs are applied by some racehorse trainers, and the potential risks associated with their use. A further study of a larger cohort is recommended because these results are valid for only the 112 trainers who responded and cannot be generalized to the equine industry.

Endoscopic recurrent laryngeal neuropathy grade prevalence in a sample of thoroughbred yearlings at public auction in South Africa (2013-2019)

Endoscopy of thoroughbred (TB) yearlings at public auctions is common in South Africa. Laryngeal function (LF) is a common concern of buyers of young TBs. Cancellation of sale because of LF abnormalities is a concern for both the vendor and the buyer, with recurrent laryngeal neuropathy (RLN) being a common cause of sale cancellation. The aim of this descriptive study was to determine the prevalence of RLN at South African premier TB yearling sales. This study was designed as a retrospective descriptive analysis of upper respiratory tract (URT) endoscopic examinations to determine RLN grade, performed at two premier TB yearling sales in South Africa. Results of buyer-requested endoscopic examination from 2013 to 2019 were included. Results from the yearling sales were analysed for prevalence of RLN grade (using Rakestraw’s 4-point system) and compared to similar previously published studies. For analysis of effects of gender on RLN grading, horses were grouped and Fisher’s exact test was used to determine if there was a relationship between gender and grade. For comparison of the effects of age on grade, and sales year on grade, a Kruskal–Wallis test was conducted. A value of p < 0.05 was considered significant. A total of 858 horses were examined out of 4149 offered for sale; there were 57.58% colts and 42.42% fillies (mean age of 18.1 months). The annual percentage for grade 1 was 84.04% ± 9.98%, for grade 2: 14.49% ± 10.69%, for grade 3: 0.71% ± 0.57% and for grade 4: 0.76% ± 0.94%. There were no other significant findings. The exclusive nature of the sale and the increasing proclivity for pre-sale scoping may have skewed the results. This study shows that RLN grade incidences in TB yearlings at public auctions in South Africa are as follows: grade 1: 84.04%, grade 2: 14.49%, grade 3: 0.71% and grade 4: 0.76%. The results were similar to that of an adult population of horses examined in South Africa in a previous study.

Ex-vivo Mechanical Testing of Novel Laryngeal Clamps Used for Laryngeal Advancement Constructs

Rostral laryngeal advancement, also known as laryngeal tie-forward, is used to treat horses for intermittent dorsal displacement of the soft palate and has a morbidity rate of about 6%. We hypothesized that a novel laryngeal clamp would prevent morbidity associated with the sutures tearing through the thyroid cartilage. Larynges (n = 35 horses) were used for ex vivo testing. For uniaxial testing, 15 equine larynges were tested in one of three laryngeal tie-forward constructs [standard laryngeal tie-forward; modified laryngeal tie-forward using a suture-button; and modified laryngeal tie-forward using a laryngeal clamp]. For biaxial testing, 20 larynges were tested in one of two treatment groups: laryngeal tie-forward and laryngeal tie-forward using a laryngeal clamp. Constructs were tested in single cycle-to-failure. Statistical analyses were performed using ANOVA for uniaxial testing and t-tests for biaxial testing. The laryngeal tie-forward using a laryngeal clamp construct was superior to laryngeal tie-forward and laryngeal tie-forward using a suture-button constructs in resistance to pullout in uniaxial testing. The laryngeal tie-forward using a laryngeal clamp presented a significantly different method of failure than the standard laryngeal tie-forward in the biaxial testing. Failure modes for each construct were primarily by suture failure at the clamp (laryngeal tie-forward using a laryngeal clamp), suture pullout through the thyroid cartilage, or, less commonly, tearing of the cricothyroid ligament (laryngeal tie-forward). In uniaxial testing, the laryngeal tie-forward using a laryngeal clamp failed most commonly due to tearing of the cricothyroid ligament, whereas the standard laryngeal tie-forward and the laryngeal tie-forward using a suture-button failed due to the tearing of the cartilage. The laryngeal clamps provided greater stiffness, load at yield, and tensile stress at yield than did the standard construct. Laryngeal clamps may offer an alternative to standard methods of anchoring the thyroid cartilage when performing the laryngeal tie-forward procedure. Further testing and clinical trials are needed to elucidate the utility of the laryngeal tie-forward using a laryngeal clamp.

Exercise Induced Laryngeal Obstruction in Humans and Equines. A Comparative Review

Dynamic obstructions of the larynx are a set of disorders that occur during exercise in equines and humans. There are a number of similarities in presentation, diagnosis, pathophysiology and treatment. Both equines and humans present with exercise intolerance secondary to dyspnea. During laryngoscopy at rest, the larynx appears to function normally. Abnormalities are only revealed during laryngoscopy at exercise, seemingly triggered by increased ventilatory demands, and quickly resolve after cessation of exercise. Lower airway disease (asthma being the most prevalent condition), cardiac disease and lack of fitness are the major differentials in both species. Laryngoscopic examination during exercise should be performed from rest to peak exertion to allow for a comprehensive diagnosis, including where the airway collapse begins, and thereafter how it progresses. Dynamic disorders with most visual similarity between humans and equines are: aryepiglottic fold collapse (both species); equine dynamic laryngeal collapse (DLC) relative to some forms of human combined supraglottic/glottic collapse; and epiglottic retroversion (both species). Quantitative grading techniques, such as airway pressure measurement, that have proven effective in veterinary research are currently being piloted in human studies. Conditions that appear visually similar are treated in comparable ways. The similarities of anatomy and certain types of dynamic collapse would suggest that the equine larynx provides a good model for human upper respiratory tract obstruction during exercise. Thus, close collaboration between veterinarians and medical personal may lead to further advancements in understanding pathophysiologic processes, and enhance the development of improved diagnostic tests and treatments that will benefit both species.

Abnormalities detected at pre-purchase examination of National Hunt racehorses presented at sale

BACKGROUND

Few studies are available concerning prevalences of abnormalities in the Thoroughbred horse population.

OBJECTIVES

Determine the prevalence of commonly observed abnormalities in a National Hunt Thoroughbred population using results of pre-purchase examinations conducted at Thoroughbred sales venues.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Veterinary pre-purchase examination certificates for 13,603 3- and 4-year-old Thoroughbred National Hunt horses from Tattersalls Ireland, Goffs Ireland and Doncaster Bloodstock Sales Ltd. (DBS) Sales were analysed. All conditions noted by the veterinarians were recorded to determine the prevalence of abnormalities.

RESULTS

Abnormalities were recorded in 73.6% of horses; 12.0% had abnormalities likely to prejudice their use for racing. Metacarpal/metatarsal exostoses and tarsal-plantar desmitis affected 17.1 and 19.4% of the sample respectively, while 9.9% were found to make abnormal respiratory noises and 5.3% had recurrent laryngeal neuropathy. Age, year of birth and sex significantly affected the prevalence of many abnormalities (P<0.001). The proportions of horses sold differed significantly between horses with and without some abnormalities, with unaffected horses significantly more likely to be sold (e.g., prejudicial findings present vs. non-prejudicial/none, 38.1% vs. 77.6% respectively, P<0.001). A range of abnormalities significantly negatively affected the price at sale (P<0.001). Significantly higher proportions of horses in the lower price categories had multiple abnormalities (P<0.001).

MAIN LIMITATIONS

The study consisted only of horses entered into store horse sales and presented for sale. Horses kept for racing or breeding purposes or horses withdrawn prior to the panel veterinary pre-purchase examination were not included. The upper respiratory tract was only examined endoscopically in horses found to have an abnormal respiratory noise.

CONCLUSIONS

A large proportion of 3- and 4-year-old Thoroughbred National Hunt horses intended for sale are affected by abnormalities. The prevalence of many abnormalities increases with age and certain abnormalities are viewed negatively by purchasers, affecting sale of the horse and achieved sale price.

Prevalence of adverse events and their effect on completion of high speed treadmill exercise tests at a single institution (2000-2015)

BACKGROUND

Decline in high speed treadmill (HSTM) exercise testing may be attributed to the rise of over-ground endoscopy and telemetric electrocardiography, in addition to concerns of adverse events during treadmill exercise resulting in injury or inadequate testing.

OBJECTIVES

To describe adverse events occurring during HSTM exercise tests at a single institution and determine their effect on likelihood of completing diagnostic HSTM exercise testing.

STUDY DESIGN

Retrospective cohort study.

METHODS

Pearson's chi-square test was used to determine if a significant difference in frequencies of adverse events existed between complete and incomplete HSTM exercise tests. Two Firth logistic regression models were used to determine likelihood of exercise test completion given the presence of any adverse event, and the likelihood of exercise test completion for each type of adverse event.

RESULTS

The majority of horses presenting for HSTM evaluation underwent exercise testing (900/1003; 90%). Eight-hundred and seven (90%) exercise tests were completed. Adverse events occurred in 136 (15%) HSTM exercise tests of which 97 (71%) did not impact ability to complete HSTM testing. Adverse events significantly but variably decreased the likelihood of HSTM exercise test completion. Sixty-six percent of incomplete exercise tests were prematurely terminated due to poor performance abnormalities during which diagnosis of poor performance cause(s) was still achieved.

MAIN LIMITATIONS

Variable personnel recorded data over the study period. Per-test rather than per-horse evaluation does not account for the effect of multiple training and testing episodes performed in the same horse.

CONCLUSIONS

This study supports the continued usage of HSTM exercise testing for examination of horses with poor performance, with adverse events occurring infrequently. Adverse events reduced the likelihood of completing HSTM exercise testing although not all adverse events affected likelihood of completion similarly. In many cases, a performance limiting problem was identified for horses in which an exercise test was considered incomplete. The Summary is available in Spanish - see Supporting information.

Ultrasonographic findings post laryngoplasty in the horse

Laryngoplasty is commonly used to treat laryngeal hemiplegia in Thoroughbred racehorses. Evaluation of the success of the laryngoplasty is traditionally determined using endoscopy. Laryngeal ultrasonography and normal ultrasonographic appearance have been reported in the standing horse, but post-laryngoplasty and ventriculectomy ultrasonographic evaluation has limited literature coverage. A prospective case series of 10 Thoroughbred racehorses with left laryngeal hemiplegia was examined ultrasonographically and endoscopically prior to 3-10 days, 30-50 days, and 6-12 months after laryngoplasty and ventriculectomy. Anatomical structures and Plica vocalis movements were described and measurements and gradings analyzed by repeated means analysis of variance (P < .05). Postsurgical ultrasonographic visualization of Ventriculus laryngis entrances was possible. The distance between Plica vocalis in exhalation was significantly larger than that during inhalation (P < .05). Pre- and postsurgical caudal Basihyoideum and rostral Cartilago thyroidea depth was significantly different in some instances (P < .05). No significant differences in the Muscularis cricoarytenoideus lateralis measurements were found. Complications in the extra-luminal structures were found in seven horses including soft tissue swelling, seroma, and hematoma. A luminal Plica vocalis abscess and Plica vocalis granuloma were also detected ultrasonographically. Ultrasonography can be used to evaluate the post-laryngoplasty horse for assessing the success of the procedure, monitoring healing, and detecting complications.

Soft Palate Modification Using a Collagen Crosslinking Reagent for Equine Dorsal Displacement of the Soft Palate and Other Upper Airway Breathing Disorders

The mechanical properties of the soft palate can be associated with breathing abnormalities. Dorsal displacement of the soft palate (DDSP) is a naturally occurring equine soft palate disorder caused by displacement of the caudal edge of the soft palate. Snoring and a more serious, sometimes life-threatening, condition called obstructive sleep apnea (OSA) are forms of sleep-related breathing disorders in humans which may involve the soft palate. The goal of this study was to investigate the effect of injecting the protein crosslinker genipin into the soft palate to modify its mechanical properties for the treatment of equine DDSP with potential implications for the treatment of snoring and OSA in humans. Ex vivo experiments consisted of mechanical testing and a wind tunnel study to examine the effect of genipin on the mechanical properties, displacement, and vibration of equine soft palates. A pilot in vivo study was completed using DDSP and control horses to test the safety and effectiveness of injecting a genipin reagent into the soft palate. The wind tunnel testing demonstrated a greater than 50% decrease in transient deformation and a greater than 33% decrease in steady-state vibrations for all doses of genipin tested. Ultimate tensile stress, yield stress, and Young's modulus were higher in the genipin-treated distal soft palate specimens by 52%, 53%, and 63%, respectively. The pilot in vivo study showed a reduction of snoring loudness in all DDSP horses and elimination of DDSP in at least one of three horses. The difficulty of using a 1-meter-long endoscopic injection needle contributed to a consistent overinjection of the equine soft palates, causing excessive stretching (pillowing) and related degradation of the tissue. These ex vivo and in vivo results demonstrated reduced vibration amplitude and flaccidity and increased strength of genipin-treated soft palates, suggesting that genipin crosslinking could become an effective and safe treatment for soft palate related breathing abnormalities.

Use of technological innovations in broadening the application of equine exercise physiology

The quadrennial International Conference on Equine Exercise Physiology (ICEEP) allows focused presentations of a variety of horse exercise- and performance-related research data in cardiorespiratory, muscle, biomechanics, nutrition, genomics, and applied physiology. The most diverse section of the ICEEP meeting has been termed variously ‘Applied Exercise Physiology’ (ICEEP 8 and 9), ‘Applied Physiology: Training Methods, Exercise Testing and Selection’ (ICEEP 7), or ‘Applied Physiology of Athletic Performance’ (ICEEP 6 and earlier). The next ICEEP meeting is scheduled to be held in Australia in 2018. In this subspeciality of equine exercise physiology, scientists attempt to apply or put into practical field use the techniques and tools developed in the more basic sciences in order to assess the performance, training, and injury of horses working and performing under true, non-laboratory conditions. The real test of the value of this subspeciality will be the increased application and sustainability of the use of laboratory techniques in the assessment of equine athletes in field settings. This review summarises exercise physiology findings prior to the widespread use of equine laboratory treadmills which have tethered investigators to the laboratory, and explains and illustrates newer, more portable, often digital technological developments which have allowed investigations to move out of the laboratory and back to the field setting where horses train and compete on a daily basis.

Dynamic upper respiratory abnormalities in Thoroughbred racehorses in South Africa

Upper airway endoscopy at rest has been the diagnostic method of choice for equine upper respiratory tract (URT) conditions. Development of high-speed treadmill endoscopy improved the sensitivity of URT endoscopy by allowing observation of the horse's nasopharynx and larynx during exercise. However, treadmill exercise may not always accurately represent the horse's normal exercise as track surface, rider, tack and environmental variables are altered. Recently, the development of dynamic overground endoscopy (DOE) has addressed some of these shortcomings. A retrospective study was undertaken to describe the URT abnormalities detected during DOE in racehorses presenting with poor performance and/or abnormal respiratory noise. Patient records of Thoroughbred racehorses undergoing DOE from November 2011 to August 2012 were reviewed. Data collected included signalment, primary complaint, distance exercised, maximum speed and dynamic airway abnormalities detected. Fifty-two horses underwent DOE for investigation of poor performance and/or abnormal respiratory noise. The main abnormalities detected included axial deviation of the aryepiglottic folds (40%), vocal cord collapse (35%), abnormal arytenoid function (33%) and dorsal displacement of the soft palate (25%). A total of 40 horses were diagnosed with one or more abnormalities of the URT (77%). Fifteen horses (29%) had a single abnormality and 25 horses (48%) had multiple abnormalities. This study showed that DOE is a useful technique for investigating dynamic disorders of the URT in racehorses in South Africa. The total number and type of dynamic pathological conditions were comparable with those identified in similar populations in other geographical locations.

Pharyngeal diameter in various head and neck positions during exercise in sport horses

Background

In equine athletes, dynamic stenotic disorders of the upper airways are often the cause for abnormal respiratory noises and/or poor performance. There are hypotheses, that head and neck flexion may influence the morphology and function of the upper airway and thus could even induce or deteriorate disorders of the upper respiratory tract. Especially the pharynx, without osseous or cartilaginous support is prone to changes in pressure and airflow during exercise. The objective of this study was to develop a method for measuring the pharyngeal diameter in horses during exercise, in order to analyse whether a change of head-neck position may have an impact on the pharyngeal diameter.

Results

Under the assumption that the width of the epiglottis remains constant in healthy horses, the newly developed method for calculating the pharyngeal diameter in horses during exercise is unsusceptible against changes of the viewing-angle and distance between the endoscope and the structures, which are to be assessed. The quotient of the width of the epiglottis and the perpendicular from a fixed point on the dorsal pharynx to the epiglottis could be used to determine the pharyngeal diameter. The percentage change of this quotient (pharynx-epiglottis-ratio; PE-ratio) in the unrestrained head-neck position against the reference position was significantly larger than that of any other combination of the head-neck positions investigated. A relation between the percentage change in PE-ratio and the degree of head and neck flexion could not be confirmed.

Conclusions

It could be shown, that the pharyngeal diameter is reduced through the contact position implemented by the rider in comparison to the unrestrained head and neck position. An alteration of the pharyngeal diameter depending on the degree of head and neck flexion (represented by ground and withers angle) could not be confirmed.

Respiratory diseases and their effects on respiratory function and exercise capacity

Given that aerobic metabolism is the predominant energy pathway for most sports, the respiratory system can be a rate-limiting factor in the exercise capacity of fit and healthy horses. Consequently, respiratory diseases, even in mild forms, are potentially deleterious to any athletic performance. The functional impairment associated with a respiratory condition depends on the degree of severity of the disease and the equestrian discipline involved. Respiratory abnormalities generally result in an increase in respiratory impedance and work of breathing and a reduced level of ventilation that can be detected objectively by deterioration in breathing mechanics and arterial blood gas tensions and/or lactataemia. The overall prevalence of airway diseases is comparatively high in equine athletes and may affect the upper airways, lower airways or both. Diseases of the airways have been associated with a wide variety of anatomical and/or inflammatory conditions. In some instances, the diagnosis is challenging because conditions can be subclinical in horses at rest and become clinically relevant only during exercise. In such cases, an exercise test may be warranted in the evaluation of the patient. The design of the exercise test is critical to inducing the clinical signs of the problem and establishing an accurate diagnosis. Additional diagnostic techniques, such as airway sampling, can be valuable in the diagnosis of subclinical lower airway problems that have the capacity to impair performance. As all these techniques become more widely used in practice, they should inevitably enhance veterinarians' diagnostic capabilities and improve their assessment of treatment effectiveness and the long-term management of equine athletes.

Complex dynamic upper airway collapse: associations between abnormalities in 99 harness racehorses with one or more dynamic disorders

REASONS FOR PERFORMING STUDY

Many horses demonstrate dynamic collapse of more than one upper respiratory tract (URT) structure during high-speed treadmill videoendoscopy (HSTV).

OBJECTIVES

To report the frequency of complex dynamic URT collapse in harness racehorses and determine if an association exists between occurrence of certain disorders.

METHODS

Retrospective study of 99 Standardbreds and Coldblooded trotters that had one or more dynamic URT disorders identified during HSTV between 1998 and 2006. The horses underwent HSTV using a protocol that included periods of free head carriage and poll flexion until fully fatigued. Dynamic abnormalities were classified as: dynamic laryngeal collapse (DLC) associated with poll flexion; axial deviation of the aryepiglottic folds (ADAF); dynamically flaccid epiglottis (FE); caudal palatal instability (PI); intermittent dorsal displacement of the soft palate (iDDSP); pharyngeal collapse (PC); alar fold collapse (AFC) and nasal flutter (NF). Cluster analysis and Fisher's exact test was performed between groups. Significance was set at P<0.05.

RESULTS

The overall incidence of complex dynamic URT collapse was 69.7%. Axial deviation of the aryepiglottic folds was significantly associated with PI (P<0.0001) and FE (P<0.0001); iDDSP was significantly associated with PI (P = 0.004) only. Dynamic laryngeal collapse associated with poll flexion was significantly associated with FE (P = 0.002). Cluster analysis confirmed strong associations between the above diagnosis groups and weaker associations between others.

CONCLUSION

Caudal PI seems to result in 2 diagnosis groupings: one that leads to ADAF and the other to iDDSP. Dynamic collapse of the margins of the epiglottis was a common finding in this study strongly associated with DLC, PI and ADAF.

POTENTIAL CLINICAL RELEVANCE

The associations between certain dynamic diagnoses identified in this study seems best explained as due to local anatomic and functional weaknesses that influence other structures through the Bernouilli principle, rather than being due to a generalised neurological disorder.

Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998-2006)

REASONS FOR PERFORMING STUDY

Two genetically and phenotypically distinct horse breeds are used for harness racing in Scandinavia: the Standardbred (SB) and Coldblooded Trotter. These racehorses have identical environmental, management and racing conditions. Therefore, this study was undertaken to identify and compare the relative prevalence of upper respiratory tract (URT) obstructive disorders in these 2 breeds.

OBJECTIVES

To determine whether these 2 phenotypically different breeds of harness racehorses have different predispositions for URT disorders.

METHODS

Retrospective study of 88 Norwegian Coldblooded Trotters (NCT) and 97 SBs referred to this hospital for URT evaluation between 1998 and 2006. Case records of all horses diagnosed with an URT disorder during resting endoscopy, and all horses undergoing high-speed treadmill videoendoscopy (HSTV) with one or more periods of induced poll flexion were evaluated. The relative prevalence of URT disorders between the 2 breeds was analysed using a Fisher's exact test.

RESULTS

There was a significant (P<0.05) breed predisposition regarding 6 URT disorders. Bilateral dynamic laryngeal collapse associated with poll flexion and flaccid epiglottis was significantly more frequent in the NCT. Alar fold collapse and nasopharyngeal collapse were significantly more frequent in SBs. Epiglottic entrapment and nasal flutter were only diagnosed in the SBs. Dynamic disorders were more common than resting disorders in both breeds.

CONCLUSION

URT obstructive disorders (dynamic laryngeal collapse associated with poll flexion, flaccid epiglottis, pharyngeal collapse, alar fold collapse, nasal flutter and epiglottic entrapment) are breed related, indicating an anatomic or functional cause. Periods of induced poll flexion during HSTV was essential to declare harness racehorses free of URT disorders.

POTENTIAL RELEVANCE

Further anatomic or physiological studies comparing these breeds could potentially provide insight into the pathogenesis of certain URT obstructive disorders. Induced poll flexion should be included in routine HSTV examinations of all harness racehorses.

Physiological measurements and prevalence of lower airway diseases in Trotters with dorsal displacement of the soft palate

REASONS FOR PERFORMING STUDY

Dorsal displacement of the soft palate (DDSP) is one of the most common obstructive conditions of the upper respiratory tract in the racehorse. This condition has a complex aetiology which may be caused or exacerbated by pharyngeal inflammation. Additionally, lower respiratory airway diseases may be associated with DDSP thereby contributing to exercise intolerance in these horses.

OBJECTIVE

The aim of this study was to measure physiological variables during a standardised exercise test and to assess the prevalence and consequences of lower respiratory airway disease in horses with DDSP.

METHODS

A total of 46 horses were included in this study: 22 in the control and 24 in the DDSP groups. All horses performed a SET with measurement of heart rate (HR) and blood lactate concentration. One hour post exercise, respiratory samples were collected for cytological and bacteriological analysis.

RESULTS

During exercise, the DDSP group had higher blood lactate concentration than the control group. According to BAL results, 50 and 63% of control and DDSP group horses, respectively, had evidence of inflammatory airway disease (IAD). In the DDSP group, 42% of horses had a syndrome of tracheal inflammation (STI) with 71% of this group having bacteria isolated at >10(5) CFU/ml.

CONCLUSIONS

Horses with DDSP showed evidence of a high prevalence of IAD and STI with an associated positive bacteriology in 55% of the cases. Even if DDSP is treated by surgery, the authors' recommendation would be to investigate the possibility of lower respiratory airway problems which may also be impacting the horse's performance and/or surgery efficiency.