Field-training in young two-year-old thoroughbreds: investigating cardiorespiratory adaptations and the presence of exercise induced pulmonary hemorrhage.

BACKGROUND: Comparatively little is known regarding the initial cardiorespiratory response of young racehorses to training. The objectives were to compare physiological parameters before and after introductory training and determine whether young Thoroughbreds show endoscopic signs of exercise-induced pulmonary hemorrhage (EIPH). Ten Thoroughbreds (20-23 months) underwent 12-weeks of introductory training, including weekly speed sessions. Two 600 m high-speed exercise tests (HSET) were performed following weeks 4 and 12 while wearing a validated ergospirometry facemask. Peak oxygen consumption (V̇O2pk) and ventilatory parameters (tidal volume, VT; peak inspiratory and expiratory flow, PkV̇I, PkV̇E; respiratory frequency, Rf; minute ventilation, V̇E) were measured. The ventilatory equivalent of oxygen (V̇E/V̇O2) and the aerobic and anaerobic contributions to energy production were calculated. Maximal heart rate (HRmax) and HR at maximal speed (HRVmax) were determined. Post-exercise hematocrit, plasma ammonia and blood lactate were measured. Evidence of EIPH was investigated via tracheobronchoscopy post-exercise. Results were compared (paired t-test, P < 0.05). RESULTS: Horses were faster following training (P < 0.001) and V̇O2pk increased 28 ml/(kg total mass.min) (28 ± 16%; P < 0.001). Ventilatory (V̇E, P = 0.0015; Rf, P < 0.001; PkV̇I, P < 0.001; PkV̇E, P < 0.001) and cardiovascular parameters (HRmax, P = 0.03; HRVmax, P = 0.04) increased. The increase in V̇E was due to greater Rf, but not VT. V̇E/V̇O2 was lower (26 ± 3.6 vs 23 ± 3.7; P = 0.02), indicating improved ventilatory efficiency. Anaerobic contribution to total energy production increased from 15.6 ± 6.1% to 18.5 ± 6.3% (P = 0.02). Post-exercise hematocrit (P < 0.001), plasma ammonia (P = 0.03) and blood lactate (P = 0.001) increased following training. Horses showed no signs of EIPH. CONCLUSIONS: Young two-year-old Thoroughbreds responded well to introductory training without developing tracheobronchoscopic evidence of EIPH.

Digital lamellar inflammatory signaling in an experimental model of equine preferential weight bearing.

BACKGROUND: Supporting limb laminitis (SLL) is a complication of severe orthopedic disease in horses and is often life-limiting, yet the pathophysiology remains obscure. HYPOTHESIS/OBJECTIVES: To investigate the role of digital lamellar inflammatory signaling in the pathophysiology of SLL using a model of unilateral weight bearing, hypothesizing that there would be evidence of lamellar inflammation in limbs subjected to the model. ANIMALS: Thirteen healthy adult Standardbred horses were used for this study (11 geldings, 2 mares; mean age 6.5 ± 2.5 years; mean body weight 458.3 ± 32.8 kg). METHODS: Randomized controlled experimental study. A steel shoe with a custom insert was applied to a randomly selected front foot of 7 horses; 6 horses were unshod and served as controls. After 92 hours, all horses were humanely euthanized, and digital lamellar samples were collected. Lamellar protein and mRNA were isolated and used to perform western blot and PCR. RESULTS: Lamellar concentrations of IL-6 mRNA were higher in SL tissue than IL HIND tissue (median [25%-75%] normalized copy number 191 [111-3060] and 48 [25-74], respectively; P=.003), and lamellar concentrations of COX-2 mRNA were higher in SL tissue than CON tissue (normalized copy number 400 [168-634] and 125 [74-178], respectively; P=.007). Lamellar concentrations of IL-1B, IL-10, and COX-1 mRNA were not significantly different between groups. The concentrations of phosphorylated (activated) STAT1 and STAT3 proteins were higher in SL (0.5 [0.35-0.87] and 1.35 [1.1-1.7], respectively) compared to CON (0.24 [0.09-0.37] and 0.31 [0.16-037]) and UL HIND (0.27 [0.19-0.37] and 0.38 [0.24-0.5]); P=0.01 and P<0.001. CONCLUSIONS AND CLINICAL IMPORTANCE: Lamellar inflammatory signaling was higher in tissue from horses subjected to prolonged unilateral weight-bearing, suggesting that these pathways could be relevant to the pathophysiology of SLL.

Equine pituitary pars intermedia dysfunction: Identifying research priorities for diagnosis, treatment and prognosis through a priority setting partnership.

Pituitary pars intermedia dysfunction (PPID) is the most prevalent endocrine disorder of older equids. To date, key research areas likely to have the greatest impact on equine health have not been identified. In human medicine, public and patient involvement is widely used to inform research agendas. This study aimed to engage with veterinary surgeons and horse owners to identify evidence gaps ('uncertainties') and prioritise these into a list of the 10 most important PPID research questions. The James Lind Alliance (JLA) Priority Setting Partnership (PSP) Framework was adapted. Questions about the diagnosis, treatment and prognosis of PPID were gathered via an online survey targeting veterinary surgeons and horse owners with experience of PPID. Thematic analysis was used to form a longlist of collated indicative research questions (CIRQs), defined by the JLA as true 'evidence uncertainties' when not answered by a published, clinically relevant, up-to-date systematic review. In an interim prioritisation survey, questions were ranked by weighted scores creating a shortlist of 25 that were taken forward to the PSP workshop, where participants reached a consensus on the top 10. Useable responses containing ≥1 question were received from 524 respondents (92.6% owners, n = 485; 7.4% veterinary surgeons, n = 39). After screening for relevance, 1,260 individual questions were included in thematic analysis, resulting in 47 CIRQs. Interim prioritisation votes for the CIRQs were received from 360 respondents. The top 10 questions prioritised at the PSP workshop focused on long-term prognosis, diagnostic accuracy, efficacy of pergolide treatment, alternative treatment/management strategies and potential treatment options for poor responders to pergolide. The quantity of questions generated indicates an extensive number of uncertainties regarding the diagnosis, treatment and prognosis of PPID. The top 10 research questions will help to inform key areas for evidence synthesis and knowledge translation, and to direct future research into areas most important to end users involved in caring for and treating animals with PPID.

Navicular Syndrome-related changes to collagen proportion of different cross-sections of the flexor tendons in equine distal forelimb.

The aim of this study was to quantify the distribution of aligned and non-aligned collagen in cross-sections of the superficial digital flexor tendon (SDFT) and deep digital flexor tendon (DDFT) in different levels of the distal forelimb of equines diagnosed with NS (Navicular Syndrome). Sixty equine forelimbs were collected. Was compared two groups (NA, Not affected vs. NS-group) by t-Student. Diagnosis of NS was based on clinical and lameness examination, diagnostic analgesia and radiological findings. The proportion of aligned and non-aligned collagens at 2 levels for the SDFT and 3 levels for the DDFT were measured by histochemical stains. The amount of aligned and non-aligned collagen in tendons were calculated using Colour-Based Segmentation function. Regarding collagen, there were significant differences in the amount of aligned collagen (NA: 21.2 ± 1.31; NS-group: 12.2 ± 4.67; p = 0.0026) and non-aligned collagen (NA: 21.8 ± 2.22; NS: 25.1 ± 1.73; p = 0.0241) at the DDFT insertion in the distal phalanx. We concluded that the flexor tendons of the forelimb in equines with NS have different proportions of collagen than those that do not present the diagnosis, indicated by histologically visible increased proportions of non-aligned collagen and decreased of aligned collagen in the extracellular matrix.

Influence of osteochondrosis on the longevity and racing performance of standardbred trotters and pacers.

OBJECTIVE: To determine the influence of clinical osteochondrosis (OC) on the short-term (2, 3, and 4-year-old) and long-term racing performance and longevity of standardbred racehorses. STUDY DESIGN: Retrospective case-control study. SAMPLE POPULATION: Standardbred racehorses from a single breeding farm born between 2009 and 2017 that survived to racing age (n = 2711). Three hundred eighty-two (14%) horses were OC-affected (829 lesions confirmed arthroscopically during surgical treatment), and 2329 (86%) horses were nonaffected. METHODS: Racing performance data were obtained from an online database and evaluated with multiple linear regression models. RESULTS: Trotters were more likely than pacers to be affected by OC (odds ratio [OR] = 1.4, 95% CI = 1.1-1.9, P = .006). Compared with nonaffected horses, long-term OC-affected horses had 8.8 fewer starts (95% CI = -14.4 to -3.2, P = .002), 1.0 fewer wins (95% CI = -1.9 to -0.1, P = .030), and 3.8 fewer total number of first through third place finishes (95% CI = -6.2 to -1.4, P < .0001). Nonaffected horses had longer careers compared with OC-affected horses, racing 0.32 years longer (95% CI = -0.52 to -0.12, P = .002). Osteochondrosis had no impact on short-term racing performance. Horses with lesions at the distal intermediate ridge of the tibia or lateral trochlear ridge of the talus had decreased performance compared with horses without these lesions. CONCLUSION: Pacers were less likely than trotters to be affected by OC. Affected horses had fewer starts and shorter careers, despite early surgical intervention. CLINICAL SIGNIFICANCE: Osteochondrosis decreases long-term racing performance in racing standardbreds.

Prevalence of cardiac arrhythmias and R-R interval variation in healthy Thoroughbred horses during official Chuckwagon races and recovery.

The prevalence and severity of cardiac arrhythmias in healthy racehorses undergoing competition is not well defined. The aim was to characterize arrhythmias in Thoroughbreds participating in official Chuckwagon races and to determine normal beat-to-beat (R-R) variability during supramaximal exercise. Electrocardiograph (ECG) recordings were obtained during pre-race, race, and active-recovery from 82 clinically healthy Thoroughbreds. ECG recordings were analyzed for arrhythmias and mean percent R-R deviation. Plasma lactate and high-sensitivity troponin (hs-cTnT) were also measured. Fifty-two ECGs were included in the analysis. Arrhythmias were seen in 48/52 horses (92%) and were predominantly isolated events. No complex rhythms were observed. During the race, 92% of horses had arrhythmias (81% supraventricular premature complex [SVPC]; 33% ventricular premature complex [VPC]). Eleven percent of racing arrhythmias were VPCs (all singlets except for two couplets). During active-recovery, 58% of horses had arrhythmias (56% SVPC; 15% VPCs): Three horses had VPC couplets and one horse had a VPC triplet. All plasma hs-cTnT were within normal limits. The measured lactate was 28.5 ± 4.5 mmol/L, confirming supramaximal exercise. R-R variation ranged between -9.5 to +18.8% during pre-race (mean heart rate [HR], 155 ± 22 beats per min [bpm]), -27.8 to +45.3% during racing (mean HR, 200 ± 9 bpm) and -16.4 to +40.1% during active-recovery (mean HR, 165 ± 14 bpm). Maximal and 1st percentile R-R shortening and lengthening were significantly greater at race than pre-race and active-recovery (P < 0.0001). Racing and active-recovery maximal R-R lengthening were significantly greater than pre-race (P = 0.0003). Supraventricular premature complexes and VPCs are prevalent in healthy horses undergoing Chuckwagon racing. R-R variation is greater during racing than has previously been described.

Cardiac arrhythmias in poorly performing Standardbred and Norwegian-Swedish Coldblooded trotters undergoing high-speed treadmill testing.

The significance of cardiac arrhythmias and their possible association with upper airway obstruction are frequently considered in the clinical investigation of poor performance. The specific aims of this retrospective study of a group of poorly performing Standardbred and Norwegian-Swedish Coldblooded trotters were to: (1) describe the overall frequency and frequency distributions of arrhythmias; (2) describe arrhythmia characteristics including percent prematurity, relative recovery cycle lengths and QRS morphology; (3) describe variability of normal RR intervals; and (4) explore possible associations between upper airway abnormalities and arrhythmia categories during peak exercise and recovery. The records of 103 trotters presented to the Norwegian University of Life Sciences for high-speed treadmill testing were reviewed. The occurrence of at least one arrhythmic event was high (77-78%) when considering all exercise periods and 6-10% prematurity criteria. Triplets, salvos, and/or paroxysmal tachyarrhythmias occurred in 8% of horses during peak exercise. Complex ventricular arrhythmias occurred in 15% of horses in the first 2 min of recovery. Evaluation of QRS morphology and return cycle lengths demonstrated areas of overlap in characteristics typically attributed to either supraventricular or ventricular arrhythmias. There was no association between airway diagnosis and arrhythmias during any exercise period. The maximum average HR during peak exercise was an excellent predicter for complex ventricular arrhythmias during recovery. Because perfect categorization of arrhythmias is not possible, future studies should report descriptive arrhythmia information. Prospective studies that evaluate various degrees of upper airway obstruction and the effect on known initiators of arrhythmogenesis are needed.

The Role of Neutrophils in the Pathophysiology of Asthma in Humans and Horses.

Asthma is a common and debilitating chronic airway disease that affects people and horses of all ages worldwide. While asthma in humans most commonly involves an excessive type 2 immune response and eosinophilic inflammation, neutrophils have also been recognized as key players in the pathophysiology of asthma, including in the severe asthma phenotype where neutrophilic inflammation predominates. Severe equine asthma syndrome (sEAS) features prominent neutrophilic inflammation and has been increasingly used as a naturally occurring animal model for the study of human neutrophilic asthma. This comparative review examines the recent literature in order to explore the role of neutrophil inflammatory functions in the pathophysiology and immunology of asthma in humans and horses.

Assessment of platelet biology in equine patients with systemic inflammatory response syndrome.

In addition to maintaining hemostasis, platelets have an important role in modulating innate and adaptive immune responses. A low platelet count has been found to be a negative prognostic factor for survival in humans and horses with critical illnesses, such as sepsis or systemic inflammatory response syndrome (SIRS). Decreased platelet aggregation, caused by in vivo activation, has been found in human patients with severe sepsis. In our prospective controlled study, we assessed platelet biology in blood samples from 20 equine SIRS cases and 120 healthy control horses. Platelet variables such as platelet count, large platelet count, clumps, plateletcrit, mean platelet volume, and mean platelet component concentration were analyzed by laser flow cytometry (Advia 2120) from K3EDTA blood and from citrate blood. Hirudin blood samples were analyzed by impedance aggregometry (Multiplate analyzer; Roche) for platelet aggregation, including spontaneous aggregation and aggregation by 4 different agonists: adenosine diphosphate (ADPtest), ADP + prostaglandin E1 (ADPtestHS), arachidonic acid (ASPItest), and collagen (COLtest). SIRS cases had significantly lower platelet counts in K3EDTA blood (p < 0.0001) compared to control horses. There were no significant differences in aggregation values between SIRS cases and controls. Non-surviving SIRS horses did not have statistically significant lower platelet counts or lower aggregation values for COLtest, ADPtest, or ADPtestHS compared to surviving SIRS horses, although 5 non-survivors were thrombocytopenic.

Hypercapnia and hyperlactatemia were positively associated with higher-grade arrhythmias during peak exercise in horses during poor performance evaluation on a high-speed treadmill.

Cardiac arrhythmias are common in horses during exercise, especially immediately post-exercise. The objectives of this study were to: (1) describe the frequency and type of cardiac arrhythmias detected in horses during incremental high-speed treadmill exercise testing (ITET); (2) determine if arterial blood gas (ABG) changes at peak and immediately post-exercise were associated with arrhythmias; and (3) determine whether upper or lower airway disease was associated with exercising cardiac arrhythmias. Horses (n = 368) presenting for an ITET underwent resting and exercising upper airway endoscopy, resting, exercising and post-exercise electrocardiography, resting and post-exercise echocardiography and exercising ABG. Arrhythmias were graded by the most severe arrhythmia present. Grade 1 arrhythmias were defined as one or two atrial (APCs) or ventricular premature complexes (VPCs), or one APC and one VPC, detected in 6.9% at peak and 16% at 0-2 min post exercise.. Grade 2 arrhythmias were >2 APCs or VPCs, or both, detected in 5.8% at peak and 16.6% at 0-2 min post exercise. Grade 3 included complex arrhythmias (couplets, triplets, R on T, multiform complexes or paroxysmal atrial or ventricular tachycardia), detected in 4.4% at peak and 7.3% at 0-2 min post exercise. Both partial pressure of arterial CO2 (PaCO2; P = 0.008) and lactate (P = 0.031) were significantly associated with arrhythmias occurring at peak exercise, but not immediately post-exercise. As PaCO2 and lactate increased, arrhythmia severity increased. Blood pH was significantly associated with grades 2 and 3 arrhythmias at 0-2 min post ITET (OR = 0.0002; P < 0.001). There was no significant association between grades 2 and 3 cardiac arrhythmias, inflammatory airway disease (IAD), or exercise-induced pulmonary hemorrhage (EIPH). When adjusted for lactate concentration (P = 0.06), higher PaCO2 concentrations in horses with and without exercising upper respiratory tract (URT) obstruction were associated with higher likelihood of grades 2 and 3 arrhythmias (P < 0.01). This study demonstrated that at peak exercise, with severe hypercapnia and hyperlactatemia, there was increased risk for grades 2 or 3 cardiac arrhythmias and, as the PaCO2 and lactate values increased further, the severity of those arrhythmias increased.

Age over 25 years, but not plasma adrenocorticotropic hormone con-cen-tration above the seasonally adjusted reference range is predictive for radio-graphically assessed changes of chronic laminitis in elderly horses.

INTRODUCTION: Endocrinopathic laminitis occurs as a consequence of hormonal derangements like pituitary pars intermedia dysfunction (PPID). The objective of the present study was to assess the occurrence of radiographic changes associated with chronic laminitis in elderly, clinically sound horses. Fifty-one horses were included in the study. Horses were assigned to different age groups, in groups according to their BCS and CNS as well as to groups with different ACTH concentrations in order to assess their risk of chronic laminitis (reported as odds ratios (OR) and confidence intervals (CI)). Horses assigned to an older age group (26-32 years) were significantly more likely to have radiographically assessed changes of chronic laminitis than horses in a younger age group (15-25 years) (OR 3.33; CI 1.05-10.59). The other variables (body condition score, cresty neck score, ACTH concentration) were not associated with an increased risk of having laminitic changes in these horses.

INTRODUCTION: La fourbure endocrinopathique survient à la suite de troubles hormonaux tels que le dysfonctionnement de la pars intermedia de l'hypophyse (DPIH). L'objectif de la présente étude était d'évaluer les changements radiographiques associés à la fourbure subclinique chez les chevaux âgés cliniquement sains. Cinquante et un chevaux ont été inclus dans l'étude. Les chevaux ont été assignés à différents groupes d'âge, en groupes en fonction de leur Body Condition Score (BCS) et de leur Cresty Neck Score (CNS) ainsi que des groupes avec différentes concentrations d'ACTH afin d'évaluer leur risque de fourbure chronique (rapportés sous forme de rapports de cotes (Odds-Ratio, OR) et d'intervalles de confiance (IC)). Les chevaux faisant partie d'un groupe d'âge plus avancé (26 à 32 ans) étaient significativement plus susceptibles de présenter des signes radiographiques de fourbure chronique que les chevaux d'un groupe d'âge plus jeune (15 à 25 ans) (OR 3,33; IC 1,05­10,59). Les autres variables (BCS, CNS, concentration d'ACTH) n'étaient pas associées à un risque accru de modifications de type fourbure chez ces chevaux.

Leptospira spp. in horses in southern Brazil: Seroprevalence, infection risk factors, and influence on reproduction.

Leptospirosis in horses is often associated with reproductive disorders. In the southern states of Brazil, horses are used for various jobs and cultural practices; nevertheless, serological surveillance for Leptospira is rare. Therefore, the objective of this study was to determine the seroprevalence of Leptospira spp. in horses in southern Brazil, as well as to identify the risk factors for infection and its impacts on reproduction. We performed microscopic agglutination tests for 12 serovars that corresponding 9 serogroup (Sejroe, Icterohaemorrhagiae, Australis, Pyrogenes, Pomona, Canicola, Grippotyphosa, Tarassovi and Ballum) in 595 samples from 60 herds. A brief history was obtained to analyze risk factors for reproductive disorders. A total of 45.9% of the tested horses were seropositive, of which the most frequent serogroups were Icterohaemorrhagiae (Icterohaemorrhagiae and Copenhageni serovars) and Ballum (Ballum serovar). Simple infections were found in 45.4% of seropositive animals, while mixed infections occurred in 54.6% of horses. There was a correlation between seropositivity and age and sex, that is, seropositivity was more frequent in animals over 6 years old and in females. There was no correlation between seropositivity and reproductive disorders. We conclude that there is a high seroprevalence of Leptospira spp. in southern Brazil with predominance of Icterohaemorrhagiae serogroup, mainly in older animals. Location, breeds, contact with dogs or other domestic animals are not risk factors, whereas gender is a risk factor. Reproductive disorders are not due to leptospirosis in the study region.

Atrial fibrillation in horses part 1: Pathophysiology.

Atrial fibrillation (AF) is the most common clinically relevant arrhythmia in horses, with a reported prevalence up to 2.5%. The pathophysiology has mainly been investigated in experimental animal models and human medicine, with limited studies in horses. Atrial fibrillation results from the interplay between electrical triggers and a susceptible substrate. Triggers consist of atrial premature depolarizations due to altered automaticity or triggered activity, or local (micro)reentry. The arrhythmia is promoted by atrial myocardial ion channel alterations, Ca2+ handling alterations, structural abnormalities, and autonomic nervous system imbalance. Predisposing factors include structural heart disease such as valvular regurgitation resulting in chronic atrial stretch, although many horses show so-called 'lone AF' or idiopathic AF in which no underlying cardiac abnormalities can be detected using routine diagnostic techniques. These horses may have underlying ion channel dysfunction or undiagnosed myocardial (micro)structural alterations. Atrial fibrillation itself results in electrical, contractile and structural remodelling, fostering AF maintenance. Electrical remodelling leads to shortening of the atrial effective refractory period, promoting reentry. Contractile remodelling consists of decreased myocardial contractility, while structural remodelling includes the development of interstitial fibrosis and atrial enlargement. Reverse remodelling occurs after cardioversion to sinus rhythm, but full recovery may take weeks to months depending on duration of AF. The clinical signs of AF depend on the aerobic demands during exercise, ventricular rhythm response and presence of underlying cardiac disease. In horses with so-called 'lone AF', clinical signs are usually absent at rest but during exercise poor performance, exercise-induced pulmonary hemorrhage, respiratory distress, weakness or rarely collapse may develop.

Effect of digital hypothermia on lamellar inflammatory signaling in the euglycemic hyperinsulinemic clamp laminitis model.

BACKGROUND: Continuous digital hypothermia (CDH) prevents lamellar failure in the euglycemic hyperinsulinemic clamp (EHC) model of laminitis, but the protective mechanisms are unclear. HYPOTHESIS/OBJECTIVES: To determine if CDH inhibits lamellar inflammatory signaling in the EHC model of laminitis. ANIMALS: Eight Standardbred horses. METHODS: Prospective experimental study. Horses underwent an EHC, with 1 forelimb treated with CDH and the other kept at ambient temperature (AMB). Horses were euthanized 48 hours after initiation of the EHC and lamellar tissue was analyzed via polymerase chain reaction (pro-inflammatory cytokine and chemokine genes-CXCL1, CXCL6, CXCL8, IL-6, MCP-1, MCP-2, IL-1ß, IL-11, cyclooxygenase 1 and 2, tumour necrosis factor-alpha [TNF-α], E-selectin, and intercellular adhesion molecule-1 [ICAM-1]) and immunoblotting (phosphorylated and total signal transducer and activator of transcription 1 [STAT1] and STAT3). RESULTS: Compared to AMB, lamellar messenger ribonucleic acid (mRNA) concentrations of CXCL6 (P =.02), CXCL8 (P = .008), IL-6 (P = .008), IL-1ß (P = .008), IL-11 (P = .008), and cyclooxygenase-2 (P = .008) were decreased in CDH. Cyclooxygenase-1 (P = .008) was increased in CDH, while CXCL1 (P = .15), MCP-1 (P = .05), MCP-2 (P = .46), TNF-α (P = .05), E-selectin (P = .15), and ICAM-1 (P = .15) mRNA were not significantly different. Compared to AMB, lamellar concentration of total STAT3 protein was decreased in CDH (P < .001), but there was no change in phosphorylated STAT3 (P-STAT3 [S727] P = .19; P-STAT3 [Y705] P = .05). There was no change in lamellar concentrations of total STAT1 (P = .75) or phosphorylated STAT1 (P-STAT1 [S727], P = .25; P-STAT1 [Y701], P = .64). CONCLUSIONS AND CLINICAL IMPORTANCE: These data add further support for the use of CDH as a first aid treatment for severe acute laminitis associated with hyperinsulinemia in horses.

Assessment of peripheral blood neutrophil respiratory burst, phagocytosis and apoptosis in obese non-insulin dysregulated horses.

Obesity is a highly prevalent condition in horses. Dysfunctional neutrophil activity has been reported in metabolically healthy obese humans, but minimal data exist regarding horses. The present study evaluated the effect of obesity on apoptosis, phagocytosis and oxidative burst activity of peripheral blood neutrophils from lean and obese non-insulin dysregulated horses. Seven lean (BCS, body condition score 4-6/9) and five obese (BCS 8-9) horses were enrolled in the study. All animals underwent two metabolic tests (OGT, oral glucose test; IRT, insulin response test) before their selection to ensure their metabolic status (non-insulin dysregulated). A single blood sample was obtained from each horse, and a discontinuous density gradient was carried out to isolate neutrophils. Phagocytosis, apoptosis and reactive oxygen species (ROS) production assays were performed for each animal. All statistical analyses were performed with unpaired two-tailed t-tests. Results indicate that neutrophils from obese non-insulin dysregulated horses have a significantly increased ROS production (P < .0001), with no changes observed on phagocytosis (P > .05) or apoptosis (P > .05) when compared to the control group. In conclusion, our results demonstrate that obesity per se, in absence of other endocrine disorders, alters neutrophil reactive oxygen species production. More research is needed to understand the role of obesity on the equine immune system of horses, and its role in the development of endocrine disorders.

Pathological bradyarrhythmia in horses.

Pathological bradyarrhythmia is rare in horses but should be especially considered when presented with a horse that has signs consistent with episodic weakness or collapse. This paper reviews the literature describing our current knowledge of, and possible mechanisms causing, clinically significant bradyarrhythmia in horses.

Automatic detection of break-over phase onset in horses using hoof-mounted inertial measurement unit sensors.

A prolonged break-over phase might be an indication of a variety of musculoskeletal disorders and can be measured with optical motion capture (OMC) systems, inertial measurement units (IMUs) and force plates. The aim of this study was to present two algorithms for automatic detection of the break-over phase onset from the acceleration and angular velocity signals measured by hoof-mounted IMUs in walk and trot on a hard surface. The performance of these algorithms was evaluated by internal validation with an OMC system and a force plate separately. Seven Warmblood horses were equipped with two wireless IMUs which were attached to the lateral wall of the right front (RF) and hind (RH) hooves. Horses were walked and trotted over a force plate for internal validation while simultaneously the 3D position of three reflective markers, attached to lateral heel, lateral toe and lateral coronet of each hoof, were measured by six infrared cameras of an OMC system. The performance of the algorithms was evaluated by linear mixed model analysis. The acceleration algorithm was the most accurate with an accuracy between -9 and 23 ms and a precision around 24 ms (against OMC system), and an accuracy between -37 and 20 ms and a precision around 29 ms (against force plate), depending on gait and hoof. This algorithm seems promising for quantification of the break-over phase onset although the applicability for clinical purposes, such as lameness detection and evaluation of trimming and shoeing techniques, should be investigated more in-depth.

Serum cortisol and thyroid hormone concentrations and survival in foals born from mares with experimentally induced ascending placentitis.

BACKGROUND: There are few publications on occurrence of nonthyroidal illness syndrome in foals and on the prognostic value of cortisol and thyroid hormone (TH) concentrations in newborn foals. OBJECTIVES: To determine serum cortisol and TH concentrations (total and free thyroxine: T4 and F T4 ; total and free triiodothyronine: T3 and F T3 ) in foals born from mares with placentitis, to determine their association with survival, and their use as prognostic markers. ANIMALS: A cohort of 29 newborn foals comprising 5 Control, 14 Low-risk, and 10 Sick foals were evaluated over the first week of life. METHODS: In this prospective study foals born to mares with experimentally-induced placentitis were assigned to Low-risk or Sick groups while foals born to control mares were classified as Control based on clinical findings. Foals were also classified as Term (n = 13), Dysmature (n = 7), or Premature (n = 9), and survival rate was recorded. Serum cortisol and TH hormone concentrations were measured at 0, 12, 24, 48, and 168 hours of life. RESULTS: Sick non-surviving foals had lower (P < .05) T3 : cortisol ratio at 12 (3.68 ± 1.06 versus 18.58 ± 2.78), 24 (5.47 ± 2.34 versus 23.40 ± 3.82), and 48 (10.47 ± 6.29 versus 26.6 ± 2.90) hours of life when compared to Sick surviving foals and lower (P < .05) T4 : cortisol ratio at 12 (75.12 ± 21.71 versus 414.47 ± 58.47) and 24 hours (127.83 ± 55.21 versus 430.87 ± 80.31) after birth than Sick surviving foals. CONCLUSION AND CLINICAL IMPORTANCE: Placental infections can impair fetal thyroid function. Low T3 : cortisol and T4 : cortisol ratios seem to be good prognostic markers in newborn foals.

Equine hydrallantois is associated with impaired angiogenesis in the placenta.

INTRODUCTION: Hydrallantois is the excessive accumulation of fluid in the allantoic cavities during the last trimester of pregnancy, leading to abdominal wall hernias, cardiovascular shock, abortion, and dystocia. It has been postulated that hydrallantois is associated with structural and/or functional changes in the chorioallantoic membrane. In the present study, we hypothesized that angiogenesis is impaired in the hydrallantoic placenta. METHOD: Capillary density in the hydrallantoic placenta was evaluated in the chorioallantois via immunohistochemistry for Von Willebrand Factor. Moreover, the expression of angiogenic genes was compared between equine hydrallantois and age-matched, normal placentas. RESULTS: In the hydrallantoic samples, edema was the main pathological finding. The capillary density was significantly lower in the hydrallantoic samples than in normal placentas. The reduction in the number of vessels was associated with abnormal expression of a subset of angiogenic and hypoxia-associated genes including VEGF, VEGFR1, VEGFR2, ANGPT1, eNOS and HIF1A. We believe that the capillary density and the abnormal expression of angiogenic genes leads to tissue hypoxia (high expression of HIF1A) and edema. Finally, we identified a lower expression of genes associated with steroidogenic enzyme (CYP19A1) and estrogen receptor signaling (ESR2) in the hydrallantoic placenta. DISCUSSION: Based on the presented data, we believe that formation of edema is due to disrupted vascular development (low number of capillaries) and hypoxia in the hydrallantoic placenta. The edema leads to further hypoxia and consequently, causes an increase in vessel permeability which leads to a gradual increase in interstitial fluid accumulation, resulting in an insufficient transplacental exchange rate and accumulation of fluid in the allantoic cavity.