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Abstract Background Parasympathetic tone activity (PTA) in response to nociceptive stimulus in conscious non‐sedated horses is unknown. Objectives Study PTA, heart rate (HR), and horse grimace scale (HGS) at rest and during mechanical nociceptive stimulation. Animals Ninety healthy young adult horses (females, males): 30 each of Friesians, Quarter Horses, and Warmbloods. Methods Prospective control study. The study consisted of habituation to equipment (Day 1), baseline recordings (Days 2 and 3), and nociceptive testing applying mild pressure to the metacarpus (Day 4). Parasympathetic tone, HR, and HGS were recorded simultaneously on Days 2 to 4. Each study lasted 30 minutes and was done in triplicate at 3 different time points per day. Results Baseline PTA was not different among breeds. It decreased in Warmbloods and Quarter Horses during placement of the stimulus device without stimulation (P

Abstract Background Detailed descriptions of clinical signs associated with radiological findings of the caudal cervical vertebral column are not available. Objectives/Hypotheses Describe the clinical features associated with neck pain or stiffness, neck‐related thoracic limb lameness, proprioceptive ataxia consistent with a cervicothoracic spinal cord or nerve lesion, and their frequency of occurrence compared with control horses. Animals A total of 223 Warmblood horses. Methods Case‐control study. Controls and cases were recruited prospectively. All horses underwent predetermined lameness and neurologic examinations. The frequency of occurrence of each clinical feature was compared between cases and controls and relative risk (RR) were calculated. Results Ninety‐six cases and 127 controls were included. Forty‐seven (49%) of the cases were classified as neurologic, 31 (32.3%) had thoracic limb lameness, and 18 (18.7%) had neck stiffness or pain or both. Focal caudal cervical muscle atrophy (46, 47.9%), hypoesthesia (38, 39.6%), patchy sweating (16, 16.7%), hyperesthesia (11, 11.5%), and pain upon firm pressure applied over the caudal cervical articular process joints and transverse processes (58, 60.4%) were only observed in cases (P

Abstract Background In 2020, a novel neurologic disease was observed in juvenile Quarter Horses (QHs) in North America. It was unknown if this was an aberrant manifestation of another previously described neurological disorder in foals, such as equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM). Hypothesis/Objectives To describe the clinical findings, outcomes, and postmortem changes with Equine Juvenile Spinocerebellar Ataxia (EJSCA), differentiate the disease from other similar neurological disorders, and determine a mode of inheritance. Animals Twelve neurologically affected QH foals and the dams. Methods Genomic DNA was isolated and pedigrees were manually constructed. Results All foals (n = 12/12) had a history of acute onset of neurological deficits with no history of trauma. Neurological deficits were characterized by asymmetrical spinal ataxia, with pelvic limbs more severely affected than thoracic limbs. Clinicopathological abnormalities included high serum activity of gamma‐glutamyl transferase and hyperglycemia. All foals became recumbent (median, 3 days: [0–18 days]), which necessitated humane euthanasia (n = 11/12, 92%; the remaining case was found dead). Histological evaluation at postmortem revealed dilated myelin sheaths and digestion chambers within the spinal cord, most prominently in the dorsal spinocerebellar tracts. Pedigree analysis revealed a likely autosomal recessive mode of inheritance. Conclusions and Clinical Importance EJSCA is a uniformly fatal, rapidly progressive, likely autosomal recessive neurological disease of QHs

Abstract Background Comprehensive descriptions of equids with granulocytic anaplasmosis (EGA) with neurologic or muscle disease and other atypical presentations are scarce in the literature. Objective Describe the clinical signs, laboratory findings, treatment, and outcome of equids with EGA with emphasis on neurologic and muscle disease. Animals Thirty‐eight horses, 1 donkey. Methods Retrospective study. Equids with EGA were included. The electronic data base was searched from January 2000 to December 2022 using the words anaplasmosis, ehrlichiosis, granulocytic, and rickettsia. Signalment and clinical data were reviewed. Data were evaluated for normality using Shapiro‐Wilk test. Parametric and nonparametric statistics were used for normally and non‐normally distributed data. Results Common (41%) and other (59%) presentations were seen in horses ≥ 4 years of age (median, 14 years) with an overrepresentation of males (77%). Neurologic disease was common (41%), mainly presenting as diffuse symmetrical proprioceptive ataxia. Brain disease was less common manifesting as obtundation and cranial nerve deficits. Muscle disease was less common, with QH breeds with the variant causing myosin heavy chain myopathy (MYHM) having severe disease. Cavitary effusion, cardiomyopathy and disseminated intravascular coagulation (DIC) were uncommon. Clinical laboratory results varied depending on disease stage. Muscle enzyme activities were significantly higher in horses with muscle disease. Outcome was favorable with prompt tetracycline treatment. Death and long‐term sequelae were not reported. Conclusions and Clinical Importance Common and atypical presentations of EGA have a favorable outcome with prompt tetracycline treatment. Quarter horse breeds with muscle disease should be genotyped for MYHM.

Abstract Background Juvenile idiopathic epilepsy (JIE) is categorized as a generalized epilepsy. Epilepsy classification entails electrocortical characterization and localization of epileptic discharges (ED) using electroencephalography (EEG). Hypothesis/Objectives Characterize epilepsy in Egyptian Arabian foals with JIE using EEG. Animals Sixty‐nine foals (JIE, 48; controls, 21). Methods Retrospective study. Inclusion criteria consisted of Egyptian Arabian foals: (1) JIE group diagnosed based on witnessed or recorded seizures, and neurological and EEG findings, and (2) control group of healthy nonepileptic age‐matched foals. Clinical data were obtained in 48 foals. Electroencephalography with photic stimulation was performed under standing sedation in 37 JIE foals and 21 controls. Results Abnormalities on EEG were found in 95% of epileptic foals (35 of 37) and in 3 of 21 control asymptomatic foals with affected siblings. Focal ED were detected predominantly in the central vertex with diffusion into the centroparietal or frontocentral regions (n = 35). Generalization of ED occurred in 14 JIE foals. Epileptic discharges commonly were seen during wakefulness (n = 27/37 JIE foals) and sedated sleep (n = 35/37 JIE foals; 3/21 controls). Photic stimulation triggered focal central ED in 15 of 21 JIE foals. Conclusions and Clinical Importance Juvenile idiopathic epilepsy has a focal onset of ED at the central vertex with spread resulting in clinical generalized tonic‐clonic seizures with facial motor activity and loss of consciousness. Electroencephalography with photic stimulation contributes to accurate phenotyping of epilepsy. Foals with this benign self‐limiting disorder might serve as a naturally occurring animal model for self‐limited epilepsy in children.

Abstract Background Rapid and accurate markers to aid diagnosis of sepsis are needed in neonatal foals. The CBC variable red blood cell distribution width (RDW) to platelet ratio (RPR) is associated with inflammatory response and linked to poor outcomes of sepsis in human patients. Hypothesis Explore the correlation of RPR with sepsis in neonatal foals and evaluate RPR predictive and prognostic value. Animals Three hundred seventeen hospitalized neonatal foals ≤7 days of age that had a CBC and physical exam performed at admission between 2012 and 2021. Methods Retrospective case‐control study. Clinical records were used to calculate sepsis scores and define groups. Red blood cell distribution width to platelet ratio was calculated and compared between groups (septic vs nonseptic) based on Kruskal‐Wallis and Wilcoxon signed‐rank tests. A multivariate logistic regression model to predict sepsis was created. The cutoff for RPR was obtained based on the maximal Youden Index. The Kaplan‐Meier method and the log‐rank test were used to estimate survival curves and compare survival rates based on RPR. Results Red blood cell distribution width to platelet ratio was significantly higher in septic foals (Median = 0.099, confidence interval [CI] [0.093; 0.108]) than in sick nonseptic (0.085, CI [0.083; 0.089]) and healthy foals (0.081, CI [0.077; 0.086]; P

Abstract The neurosteroid allopregnanolone (ALLO) is under investigation as a treatment for benzodiazepine‐refractory status epilepticus (SE). Here, we assess the cardiopulmonary safety of intravenous ALLO by itself and after a clinically recommended dose of midazolam (MDZ) in two healthy adult beagles. Each dog received ALLO (1 mg/kg, IV), and after a washout period of 2 weeks, each dog was dosed with MDZ (0.2 mg/kg, IV) followed 10 minutes later by ALLO. Behavioral state, vital signs, arterial blood gases, blood chemistries, and plasma ALLO concentrations were monitored for up to 6 hours after dosing. The dogs appeared sleepy but were fully responsive after both treatments. No depression of mean arterial pressure or respiratory rate was noted. Blood gas measurements failed to show evidence of drug‐induced acute respiratory acidosis. Estimated maximum plasma ALLO concentrations were in the range of 1500 to 3000 ng/ml. The results indicate that intravenous ALLO can be used safely to treat benzodiazepine‐refractory SE, even when administered shortly after a benzodiazepine.

Abstract Background A standardized protocol for electroencephalography (EEG) under standing sedation for the investigation of epilepsy in foals is needed. Hypothesis/Objectives To evaluate a modified standardized EEG protocol under standing sedation using sublingual detomidine hydrochloride in Egyptian Arabian foals. Animals Nineteen foals (controls, 9; juvenile idiopathic epilepsy [JIE], 10). Methods Descriptive clinical study. Foals were classified as controls or epileptic based on history or witnessed seizures and neurological examination. Foals were sedated using sublingual detomidine hydrochloride at a dosage of 0.08 mg/kg to avoid stress associated with injectable sedation. Once foals appeared sedated with their heads low to the ground and with wide base stance (30 minutes), topical lidocaine hydrochloride was applied at the determined locations of EEG electrodes. Fifteen minutes were allowed for absorption and electrodes were placed, protected, and EEG recording performed. Results Level of sedation was considered excellent with no need of redosing. The EEG recording lasted from 27 to 51 minutes and provided interpretable data. Epileptic discharges (ED) were noted predominantly in the central‐parietal region in 9 of 10 epileptic foals. Photic stimulation triggered ED in 7 of 10 epileptic foals and in none of the controls. Foals were not oversedated and recovered uneventfully. Conclusions and Clinical Importance Sublingual detomidine hydrochloride is a safe, painless, simple, and effective method of sedation for EEG recording in foals. Sublingual sedation allowed the investigation of cerebral electrical activity during states of sleep and arousal, and during photic stimulation for the investigation of epilepsy in foals.

Abstract Background Cerebrospinal fluid (CSF) is highly labile and delayed processing might alter results of analysis. Hypothesis/Objectives To determine the effects of time and addition of autologous serum on cytological evaluation of CSF. Animals Ten client‐owned adult horses requiring euthanasia. Methods Prospective study. Serum and CSF were collected from each horse before and within 10 minutes after euthanasia. CSF samples were divided into 15 aliquots (2 mL each); 1 aliquot was submitted for routine CSF analysis within 60 minutes of collection. Four drops of autologous serum were added to 7 of the aliquots, and stored at 4°C (serum group); the remaining 7 samples were stored unaltered at 4°C (control group). Total nucleated cell count (TNCC) and cell morphology score were done at T4, T8, T12, T24, T48, T72, and T96 hours after collection. Protein concentration was measured in the control group at T0 and T96 hours. Results The cell morphology scores were significantly different in the control group at T48 (median 2, range 0‐4), T72 (2, 0‐4), and T96 (3, 0‐4) in comparison to T0 (1). No change was observed in the serum group. TNCC remained stable over time in both groups. No statistically significant difference in CSF protein concentration was found between T0 and T96. Conclusions and Clinical Importance The addition of autologous serum to an aliquot of CSF sample before shipping improves the preservation of cell morphology up to 96 hours after collection.

Abstract Background Trigeminal‐mediated headshaking (TMHS) in horses is a form of neuropathic pain of undetermined cause that often results in euthanasia. The role of microbiota in TMHS has not been investigated in diseased horses. Objective To investigate if gastrointestinal microbiota in the cecum is different in horses with TMHS compared to a control population, during a summer season with clinical manifestations of disease. Animals Ten castrated horses: five with TMHS and five neurologically normal controls. Methods All horses were sourced from our institution and kept under the same husbandry and dietary conditions. All horses were fed orchard grass hay for 30 days and then were euthanized due to chronic untreatable conditions including TMHS and orthopedic disease (control group). Caecal samples for microbiota analysis were collected within 20 min after euthanasia. Sequencing was performed using an Illumina MiSeq platform and the microbiome was analyzed. Results The caecal microbiota of horses with TMHS was similar to control horses in terms of diversity but differed significantly with Methanocorpusculum spp. having higher abundance in horses with TMHS. Conclusions and clinical importance Methanocorpusculum spp. was more abundant in the cecum of horses with TMHS. However, its role in disease is unknown. Furthermore, it could also represent an incidental finding due to our small population size.

Abstract Background Sidewinder gait in horses is poorly understood and characterized by walking with the trunk and pelvic limbs drifting to 1 side. Hypothesis/objectives To report causes, clinical and diagnostic features. Animals Horses examined at 2 institutions. Materials and Methods Retrospective study (2000‐2019). Cases with sidewinder gait, neurological and orthopedic examination, and diagnostic work up or postmortem evaluation were included. Descriptive statistics were performed. Results Twenty‐four horses (mean age 18.9 years) of various breeds and both sexes were included. Onset was acute (N = 10), subacute (N = 6), and insidious (N = 8). Electromyography and muscle biopsy supported neurologic disease and further aided in localizing site of lesion (N = 9/9). Neurologic causes included dynamic thoracolumbar spinal cord compression (N = 5), equine protozoal myeloencephalitis (N = 4, confirmed and presumed [2 each]), thoracic myelopathy of unknown etiology (N = 4), gliosis (N = 2), and thrombosis of thoracic spinal cord segments (N = 1). Non‐neurologic causes included osteoarthritis of the coxofemoral joint (N = 4), multiple displaced pelvic fractures (N = 2), bilateral rupture of the ligamentum capitis ossis femoris (N = 1), and severe myonecrosis of multiple pelvic limb muscles (N = 1). Case fatality was 79%. Conclusion and Clinical Importance Sidewinder gait is usually observed in older horses and can have neurologic or musculoskeletal etiologies. Electromyography can be used as a diagnostic aid to determine neurologic versus non‐neurologic disease and further localize those of neurologic origin. The condition often has a poor prognosis for function and life.

Abstract Background Transient hypothalamic‐pituitary‐adrenal axis dysfunction occurs in critically ill foals with sepsis and neonatal maladjustment syndrome (NMS). Cortisol is the most commonly measured steroid. However, a complex interaction of various steroid compounds might play a role in pathophysiology of this disorder. Objective To identify steroid compounds present at high concentrations at birth that rapidly and steadily decrease within the first 7 days of life in healthy foals and that might be supportive diagnosis of NMS and other neonatal disorders. Animals Ten healthy neonatal Quarter Horse foals (5 females and 5 males). Methods Prospective study. Blood was collected in heparinized tubes within 30 minutes after birth, and at 12, 24, 48, 72, 96, 120, 144, and 168 hours of age. Plasma was separated and a panel of steroid compounds was analyzed using liquid chromatography‐mass spectrometry. A nonlinear regression model was used to determine decay concentrations over time. Confidence intervals (CIs) were calculated and significance was set a P ≤ .05. Results Five compounds were identified: pregnenolone, progesterone, deoxycorticosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate. Pregnenolone and progesterone concentrations rapidly decreased by 24 hours of age and remained low throughout the first 7 days of life. Their half‐life (95% CI) was short at 3.7 (3.4, 4.0) and 4.5 (2.8, 6.1) hours, respectively. No statistical differences in the concentrations of these compounds were found between males and females. Conclusions and Clinical Relevance Progesterone might be a useful marker for identifying continuous endogenous production of neuroactive steroids in foals with suspected NMS and other neonatal diseases.

Abstract Background Oral administration of magnesium and boron might have a beneficial effect on headshaking behavior in horses. Objective Evaluate the effects of oral magnesium alone or in combination with boron on headshaking behavior in affected horses. Animals Twelve geldings (6 healthy controls and 6 affected). Methods Prospective randomized controlled dietary trial over 42 days in 12 horses (6 horses diagnosed with trigeminal‐mediated headshaking and 6 unaffected healthy controls). All horses received a hay diet and were randomized into 3 treatment groups: pelleted feed combination (PF), pelleted feed combination with magnesium (M), and pelleted feed combination with magnesium‐boron (MB) with a week washout of hay only between treatments. Headshaking behavior and biochemical blood variables were assessed at baseline (hay only) and then after each week of supplementation. Results All 3 diet interventions increased blood ionized and total magnesium. Groups M and MB further increased Mg2+ when compared to PF. Horses receiving treatments had a significant reduction in headshaking behavior, as measured by incidence rate ratio (IRR), when compared to unsupplemented hay diet (44% for PF, IRR, 0.558; CI, 0.44, 0.72; P

Phenobarbital is a common drug used to manage epilepsy in goats. However, the recommended dose and dosing frequency are based on studies in dogs and horses. Studies describing the pharmacokinetics of phenobarbital when administered orally and assessing changes in behavior with concurrent electroencephalogram (EEG) readings are warranted in goats. The objectives of this study were to determine the bioavailability of orally administered phenobarbital and determine the effect of phenobarbital on brain activity using EEG in healthy goats. A cross-over design with 8 non-pregnant goats was performed. The goats were administered phenobarbital intravenously at 10 mg/kg, followed by a 2 week wash out period, and then administered phenobarbital, orally, at 10 mg/kg. Plasma sample determination of phenobarbital concentrations were collected at 13 time points. Continuous EEG readings with simultaneous video recording for 12 h was performed to determine the state of vigilance using a behavior scoring system prior to and after phenobarbital administration. Bioavailability of phenobarbital was 24.9%. Mean ± SD for half-life was similar between the oral (3.80 ± 0.826 h) and intravenous (4.0 ± 0.619 h) routes. Time to observed maximum concentration (Tmax), and maximum plasma concentration (Cmax) for the oral administration were 1.75 ± 0.46 h and 4,478.7 ± 962.4 ng/mL, respectively. Clearance was 152.5 ± 102.7 ml/h/kg. Area under the curve from zero to infinity (AUC0→∞) was 155,813 ± 218,448 and 38,763 ± 9,832 h*ng/mL for the intravenous and oral administration routes, respectively. Behavior score at 3 h after phenobarbital administration was different (P = 0.0002) from the score prior to administration for the oral administration route. In contrast, behavior scores before administration of phenobarbital and each time point after administration were not different (P >0.05) for the intravenous administration route or other oral administration route time points. Bioavailability of phenobarbital was poor, and the half-life was very short due to a high clearance. Doses >10 mg/kg should be considered when phenobarbital is administered orally in goats.

Abstract Background It is currently unknown if the intrathecal administration of a high dose of allogeneic mesenchymal stem cells (MSCs) is safe, how MSCs migrate throughout the vertebral canal after intrathecal administration, and whether MSCs are able to home to a site of injury. The aims of the study were: 1) to evaluate the safety of intrathecal injection of 100 million allogeneic adipose-derived MSCs (ASCs); 2) to assess the distribution of ASCs after atlanto-occipital (AO) and lumbosacral (LS) injection in healthy horses; and 3) to determine if ASCs homed to the site of injury in neurologically diseased horses. Methods Six healthy horses received 100 × 106 allogeneic ASCs via AO (n = 3) or LS injection (n = 3). For two of these horses, ASCs were radiolabeled with technetium and injected AO (n = 1) or LS (n = 1). Neurological examinations were performed daily, and blood and cerebrospinal fluid (CSF) were evaluated prior to and at 30 days after injection. Scintigraphic images were obtained immediately postinjection and at 30 mins, 1 h, 5 h, and 24 h after injection. Three horses with cervical vertebral compressive myelopathy (CVCM) received 100 × 106 allogeneic ASCs labeled with green fluorescent protein (GFP) via AO injection and were euthanized 1–2 weeks after injection for a full nervous system necropsy. CSF parameters were compared using a paired student’s t test. Results There were no significant alterations in blood, CSF, or neurological examinations at any point after either AO or LS ASC injections into healthy horses. The radioactive signal could be identified all the way to the lumbar area after AO ASC injection. After LS injection, the signal extended caudally but only a minimal radioactive signal extended further cranially. GFP-labeled ASCs were not present at the site of disease at either 1 or 2 weeks following intrathecal administration. Conclusions The intrathecal injection of allogeneic ASCs was safe and easy to perform in horses. The AO administration of ASCs resulted in better distribution within the entire subarachnoid space in healthy horses. ASCs could not be found after 7 or 15 days of injection at the site of injury in horses with CVCM.

Intracranial neoplasia in horses is rare compared to other species. Detailed information such as neurological, electroencephalographic, and histopathological examination of horses with intracranial neoplasia associated with seizures is scarce in the literature. Furthermore, ganglioglioma has not been reported in the horse. A 7-year-old Quarter horse cross Paint gelding was examined due to recurrent seizure-like episodes of 1-year duration. The seizures had been increasing in frequency and length, occurring up to 20 times a day at the time of presentation. Neurological examination revealed intermittent obtundation and multiple left sided abnormalities consisting of upper motor facial and tongue hemiparesis, facial hyperesthesia and cervical hypoesthesia, proprioceptive deficits, thoracic limb hypermetria upon head elevation; and intermittent paroxysmal activity consistent with seizures. Cranial nerve reflexes were normal. Vocalization, conjugate vertical nystagmus, intermittent blindness, left sided head tilt and flexion of neck, and lack of response to environmental stimuli were observed during seizure activity. A right sided cerebrothalamic disease was suspected. An electroencephalogram confirmed seizure activity with main focus on the right side at the central, parietal, and occipital regions further supporting neuroanatomical localization. Additionally, subclinical paroxysmal activity was noted on the electroencephalogram. A ganglioglioma was identified in the right cerebrothalamic area, and other cranial parts of the brainstem based on immunohistochemical examination. To the authors' knowledge this is the first report of intracranial ganglioglioma in the horse. This intracranial neoplasia should be added to the possible causes of intracranial masses and seizures in horses.

Entrapped, stranded and recumbent equids often require emergency rescue. The success of the rescue is often affected by secondary injuries from struggling of the horse to rise and from injury secondary to attempted rescue by pulling on the head or limbs of the equid. Therefore, having ready access to simplified rescue equipment which can be easily applied would be desirable. The devices currently available for these manipulations are not always readily available at the site of an incident. Here, we describe and illustrate the step-by-step use of a Loops System consisting of 183 cm round slings, which can be positioned on the recumbent horse utilizing commercially available and reasonably priced equipment. The Loops System is basically composed of four round slings placed in such a way that utilizes the skeletal system for support. The procedures are illustrated utilizing a recumbent life-size horse model or mannequin. We suggest that the Loops System kit may allow enhanced ability for responders to provide care to a recumbent horse.

Comprehensive reports of the caseload of donkeys and mules in veterinary hospitals in the United States are lacking. We compiled the information of the caseload of donkeys and mules at the Veterinary Medical Teaching Hospital at the University of California, Davis for a ten-year period, from 2008 to 2017. The overall equid caseload was 94,147, of which 996 (1.06%) were donkeys and mules. Most of the neonates seen were mules. Most miniature donkeys were between 2 and 10 years of age, and standard donkeys and mules were 10 to 20 years old. The body condition scores were predominantly high, especially in donkeys. Most miniature and standard donkeys resided in sanctuary and rescue farms and their use was not stated. Most mules were used for riding, packing or driving. Medical complaints represented 62% of the total visits and wellness visits represented 38% of total visits. The donkeys and mules in the case population described here received a good standard of veterinary care with regular vaccinations, deworming, routine dental care, and treatment of ailments. Our study is the first report of the life expectancy, use, body condition, preventative health and veterinary medical care of a population of donkeys and mules in the western United States.

Stranded and recumbent equids often require emergency rescue, and a successful rescue often requires vertical lifting of the animal. Currently, the devices used for vertical lifting of equids are not readily available at an incident or urgent situation. The current study describes and evaluates the use of a simple lift device utilizing commercially available, and reasonably priced, equipment. The system, referred to as the Loop Vertical Lift System or Loops System, is basically composed of four round slings placed in such a way that utilizes the skeletal system for support. The study demonstrates the lifting of six standing, sedated adult horses for 3 min without adverse effects. In conclusion, this novel lift system is an affordable, practical and quick alternative to rescue a stranded or recumbent horse that requires a brief vertical lift of the animal. In contrast, for longer-term lifting and support, other devices such as the UC Davis Large Animal Lift, the Anderson Sling Support Device, or the Animal Rescue and Transport Sling (ARTS) should be used as deemed appropriate.

Trigeminal-nerve-mediated headshaking represents a major welfare challenge for owners and veterinarians and is caused by a low threshold firing of the trigeminal nerve resulting in pain manifested as violent head jerking that often terminates the horse’s career and life due to poor quality of life and suffering. As metabolic changes such as acid–base status and electrolytes play a role in nerve firing, this study sought to assess the effects following administration of hypertonic solutions on headshaking behavior in affected horses. This prospective randomized controlled crossover design utilized six horses affected with trigeminal-mediated headshaking and three treatment groups receiving intravenous administration of 5% dextrose solution at 2 mL/kg bwt (DS), NaCl 7.5% at 4 mL/kg bwt (HS), or NaHCO3 8.4% at 2 mmol/kg bwt (HB). Horses were assessed for headshaking behavior changes at times T0 (baseline, before infusion) and T15, 30, 60, 120 min post infusion. Venous blood variables: pH, HCO3−, standard base excess (SBE), Na+, Cl−, K+, Ca2+, Mg2+, total magnesium (tMg), glucose, and lactate were measured at T0 (baseline, before infusion) and T5, 15, 30, 60, 120 min post infusion. Strong ion difference (SID) and anion gap (AG) were calculated for each time point. With HB treatment, there was greater than 50% reduction in headshaking rate. There was an effect of time on increasing headshaking rate. There was an effect of breed on headshaking rate. Changes in blood parameters following DS were virtually absent. Infusion of HS caused mild changes and did not vary much from baseline except for SID and AG. Only infusion of HB caused blood pH and HCO3− to be outside of the physiologic range (alkalemia and metabolic alkalosis, respectively), SBE to double or triple, AG to decrease, and SID to increase compared to baseline. Infusion of DS was followed by increase in blood glucose and decrease in blood Na+. Infusion of HS was followed by increase in Na+ and Cl− and decrease in Mg2+. Infusion of HB was followed by decrease in Mg2+. Blood tMg, K+, and Ca2+ decreased slightly, but did not vary greatly from baseline following any of the treatments, remaining within physiologic ranges. Changes in blood composition were transient. Among all treatments, only HB had an effect on headshaking rate. The limited effects following these fluids were likely due to normal mechanisms of regulation of blood levels of pH and electrolytes. Further investigations of changes in electrolytes that might affect nerve firing should be explored.

Horses are a precocious species that must accomplish several milestones that are critical to survival in the immediate post-birth period for their survival. One essential milestone is the successful transition from the intrauterine unconsciousness to an extrauterine state of consciousness or awareness. This transition involves a complex withdrawal of consciousness inhibitors and an increase in neuroactivating factors that support awareness. This process involves neuroactive hormones as well as inputs related to factors such as cold, visual, olfactory, and auditory stimuli. One factor not previously considered in this birth transition is a yet unreported direct neural reflex response to labor-induced physical compression of the fetus in the birth canal (squeezing). Neonatal maladjustment syndrome (NMS) is a disorder of the newborn foal characterized by altered behavior, low affinity for the mare, poor awareness of the environment, failure to bond to the mother, abnormal sucking, and other neurologically-based abnormalities. This syndrome has been associated with altered events during birth, and was believed to be caused exclusively by hypoxia and ischemia. However, recent findings revealed an association of the NMS syndrome with the persistence of high concentrations of in utero neuromodulating hormones (neurosteroids) in the postnatal period. Anecdotal evidence demonstrated that a novel physical compression (squeeze) method that applies 20 min of sustained pressure to the thorax of some neonatal foals with this syndrome might rapidly hasten recovery. This survey provides information about outcomes and time frames to recovery comparing neonatal foals that were given this squeeze treatment to foals treated with routine medical therapy alone. Results revealed that the squeeze procedure, when applied for 20 min, resulted in a faster full recovery of some foals diagnosed with NMS. The adjunctive use of a non-invasive squeeze method may improve animal welfare by hastening recovery and foal–mare interactions that minimize health problems. This would also avoid or reduce costs arising from hospitalization associated with veterinary and nursing care that sometimes leads owners to elect for euthanasia.