Study of arterial blood pressure in newborn foals using an electronic sphygmomanometer

An electronic sphygmomanometer which functions on oscillometric principles, was used to measure arterial blood pressure in foals. Its accuracy was assessed by comparison with results obtained by direct measurement in anaesthetised pony foals, aged 34 to 64 days. Correlations between data obtained by the two methods were highly significant but the sphygmomanometric readings were consistently lower than those obtained by direct measurement. An equation was derived from the pooled values for mean, systolic and diastolic pressure measurements. This was used as a correction factor when the oscillometric method was employed in the field on Thoroughbred foals, during the first three days post partum, and on pony foals during the first day only. There were no significant differences between systolic, diastolic and mean values in Thoroughbreds on Days 1, 2 or 3 after birth. Measurements recorded on the first day after foaling were significantly lower (P less than 0.025) in ponies than in Thoroughbreds. Blood pressure measurements in Thoroughbreds and ponies were substantially higher than those reported previously using the ultrasonic Doppler technique.     

Failure of Calcium Channel Blockade to Prevent Intra-abdominal Adhesions in Ponies

Intra-abdominal adhesions were created by localized serosal trauma in 11 adult ponies at three locations on the small intestine. Six ponies received verapamil hydrochloride (0.2 mg/ kg) subcutaneously every eight hours for three days, and five ponies received an equal volume of saline solution at the same intervals. The investigators were not informed which treatments the ponies received. Systolic, diastolic, and mean carotid arterial pressures and heart rates were measured six hours before surgery, and then 0.5, 1, 1.5, and 8 hours after the first treatment on each day for three days. One pony was euthanatized on day 13 because of colic, and the other 10 ponies were euthanatized 14 days after surgery. Scoring methods were used to assess the severity of adhesion formation and to grade the histologic appearance of the abraded sites. No significant differences were found for rectal temperature, packed cell volume, total plasma proteins, heart rate, and systolic, diastolic, or mean arterial pressures between control and verapamil-treated ponies. No significant differences were detected between the treatment groups for adhesion scores per abraded site, total adhesion scores per pony, the total number of adhesions per pony, or in the histologic scores.     

Why Are Mares with Pneumovagina Susceptible to Bacterial Endometritis? A Personal Opinion

Pneumovagina is the abnormal presence of air in the vagina, which may lead to pneumometra and endometritis. Predisposing factors are abnormal perineal conformation and weakness of the vestibulovaginal sphincter. This report examines why ponies and some other breeds are less susceptible to pneumovagina than Thoroughbreds and consequently less susceptible to endometritis. Observations on vaginal ballooning during vaginoscopic examination led to the conclusion that there is a fundamental difference in intra-abdominal pressures between horses and ponies, and between mares with high or low body condition scores. This difference in the extreme cases, for example, a small fat pony versus a large thin Thoroughbred, means that the pressure gradient in the former is from the uterus through the vagina to the exterior, whereas the case is reversed in the latter. Although the uterus is at a negative pressure relative to the exterior, evacuation of fluids is seriously disadvantaged, leading to an inability to resolve uterine infections.     

Cardiovascular, acid-base, electrolyte, and plasma volume changes in ponies developing alimentary laminitis.

Twelve Shetland ponies were fed a high-starch ration. Seven ponies which had a transitory metabolic acidosis developed laminitis 56 hours (+/- 3.5, SEM) after overfeeding. These ponies also developed persistent hypokalemia, hyperthermia, and increased heart rate 24 hours before the onset of lameness. Serum sodium, serum chloride, hematocrit, plasma volume, and blood volume were unchanged. At the onset of clinical signs of laminitis, cardiac output and blood pressure increased, but total peripheral resistance was unchanged. None of the measured or calculated values predicted the onset of laminitis. Hypertension appeared to be a response to, rather than a cause of, lameness. Three of the remaining ponies apparently died of shock 29.3 +/- 2.7 hours after overfeeding. All 3 had severe metabolic acidosis; decreased cardiac output, systemic arterial pressure, and plasma volume; and increased hematocrit, total peripheral resistance, and pulmonary vascular resistance. The 11th pony was unaffected and the 12th pony was euthanatized.     

Turbidimetric measurement of IgG(T) in the serum of healthy Thoroughbreds and ponies

The turbidimetric analysis of IgG(T) in the serum of horses is described. Reference values are provided for 'worm-free' ponies (2.6 +/- 0.7 g/litre), stabled Thoroughbreds two years old and over (4.1 +/- 1.3 g/litre), grazing Thoroughbred broodmares (7.1 +/- 2.4 g/litre) and regularly wormed adult and young ponies grazing pasture contaminated with intestinal parasite eggs and larvae.     

A comparative study of bovine herpesvirus 1247 and equine herpesvirus 1 in ponies.

The clinical and immunological response of ponies exposed to a bovine herpesvirus isolate and equine herpesvirus 1 were compared. Each virus was inoculated into two ponies by the intranasal route. One uninoculated pony was used with each group as a contact control. The four inoculated ponies developed a mild rhinitis with an increase in rectal temperature. Virus was recovered from nasal secretions collected from the four inoculated and one contact pony. All ponies developed a serum neutralizing antibody to each virus. The data show that the two viruses are similar.     

Estimation of urinary flow rate in weanling and yearling horses

In an attempt to validate the use of urinary creatinine concentration as an index of urinary flow rate, a series of timed quantitative urine collections were done on several groups of weanling and yearling ponies and Thoroughbreds. A total of 411 urine samples were generated by 19 ponies and 12 Thoroughbreds. Urinary flow rates and urinary creatinine concentrations were measured. When all the data were examined, urinary flow rates were independent of creatinine concentrations. However, for any given animal, daily urinary creatinine excretion was constant over several days, and urinary creatinine concentrations were related to urinary flow rates in a negative curvilinear fashion. Urinary flow rates in young horses can be estimated from urinary creatinine concentrations, but separate curves relating the 2 variables must first be derived for each animal.     

The pharmacokinetics of meclofenamic acid in the horse

The pharmacokinetics of meclofenamic acid were studied in Thoroughbred horses and in ponies. After intravenous (i.v.) administration of either 2 mg/kg or 4 mg/kg sodium meclofenamate the elimination half-life was of the order of 0.9 h while the volume of distribution was found to be 0.128 litre/kg. Elimination was in accordance with a one-compartment model. Following oral administration of either meclofenamic acid (4 mg/kg) or sodium meclofenamate (4 mg/kg) a much longer terminal half-life than that calculated for K _el from i.v. data was found. This anomaly indicated that the 'flip-flop' phenomenon was present, i.e. K _a exceeded K _el. More rapid and higher peak levels occurred following sodium meclofenamate than meclofenamic acid, although total bioavailability was similar. Studies in ponies with meclofenamic acid showed a lower absorption than that found in Thoroughbreds. Overnight fasting before meclofenamic acid administration did not alter the rate or extent of absorption. Intramuscular administration of sodium meclofenamate resulted in low plasma concentrations and after 25 h only 46% of the drug had been absorbed.     

Effects of training on maximum oxygen consumption of ponies

OBJECTIVES: To establish maximum oxygen consumption VO2max) in ponies of different body weights, characterize the effects of training of short duration on VO2max, and compare these effects to those of similarly trained Thoroughbreds. ANIMALS: 5 small ponies, 4 mid-sized ponies, and 6 Thoroughbreds. PROCEDURE: All horses were trained for 4 weeks. Horses were trained every other day for 10 minutes on a 10% incline at a combination of speeds equated with 40, 60, 80, and 100% of VO2max. At the beginning and end of the training program, each horse performed a standard incremental exercise test in which VO2max was determined. Cardiac output (Q), stroke volume (SV), and arteriovenous oxygen content difference (C [a-v] O2) were measured in the 2 groups of ponies but not in the Thoroughbreds. RESULTS: Prior to training, mean VO2max for each group was 82.6 = 2.9, 97.4 +/- 13.2, and 130.6 +/- 10.4 ml/kg/min, respectively. Following training, mean VO2max increased to 92.3 +/- 6.0, 107.8 +/- 12.8, and 142.9 +/- 10.7 ml/kg/min. Improvement in VO2max was significant in all 3 groups. For the 2 groups of ponies, this improvement was mediated by an increase in Q; this variable was not measured in the Thoroughbreds. Body weight decreased significantly in the Thoroughbreds but not in the ponies. CONCLUSIONS AND CLINICAL RELEVANCE: Ponies have a lower VO2max than Thoroughbreds, and larger ponies have a greater VO2max than smaller ponies. Although mass-specific VO2max changed similarly in all groups, response to training may have differed between Thoroughbreds and ponies, because there were different effects on body weight.     

Respiratory airflow patterns in ponies at rest and during exercise.

The exercise-induced changes in the equine breathing pattern were studied by analyzing tidal breathing flow-volume loops recorded in ten ponies both at rest and during a standardized exercise. Airflow, tidal volume, esophageal pressure and mask pressure were simultaneously recorded before, during and after a treadmill exercise. From the collected data, respiratory frequency and total pulmonary resistance were calculated, tidal breathing flow-volume loops were retraced using a computerized method and loop indices were measured for each period of the experimental protocol. For each pony, results of three consecutive daily measurements were averaged. The exercise loop indices were compared with the corresponding resting values using a one-way analysis of variance. The significantly changed indices were correlated with respiratory frequency and total pulmonary resistance. Several types of respiratory patterns were observed at rest as well as during exercise, although each pony was relatively constant in its own pattern of breathing. Most resting inspiratory and expiratory airflow curves were found to be biphasic. When ponies started running, the airflow developed an increasingly rectangular pattern. During strenuous exercise, both inspiratory and expiratory airflow curves showed a substantial increase of the volume acceleration and tended to a plateau. The loop indices relating the expiratory to the inspiratory airflow were significantly increased compared with their rest values. Correlations of these indices with respiratory frequency and total pulmonary resistance were weak.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of flunixin meglumine on blood pressure and fluid compartment volume changes in ponies given endotoxin

A study was conducted to determine whether body fluids undergo a net shift from one compartment to another during endotoxin-induced shock in the pony, and whether flunixin meglumine alters these endotoxin-induced changes in the volumes of body fluid compartments. Total blood, RBC, and plasma volumes were determined, using 51Cr-labeled RBC and PCV that were corrected for trapped plasma. Total body water was measured by distribution of 3HOH. Arterial blood pressure was measured directly, using a blood pressure transducer. Treatment (flunixin meglumine, 1.1 mg/kg of body weight) was given to 6 of the 12 ponies 1 minute before an IV injection of Escherichia coli endotoxin (100 micrograms/kg of body weight, LD100). The PCV and RBC volume increased in both groups; however, the hemoconcentration was less in flunixin meglumine-treated ponies. In nontreated ponies, total blood volume and plasma volume decreased significantly during the first hour after endotoxin administration. In treated ponies, total blood volume did not vary significantly, and plasma volume decreased only slightly. In both groups, the increase in PCV was apparently due to splenic contraction, which increased the number of circulating RBC. Hemoconcentration was further increased in nontreated ponies by the loss of plasma into the interstitial space. Flunixin meglumine reduced plasma loss, minimized hemoconcentration, and maintained normal blood volume. Total body water remained constant in treated and nontreated ponies.     

Equine serum lipids: serum lipids and glucose in Morgan and Thoroughbred horses and Shetland ponies.

Concentrations of serum phospholipids, triglycerides, total cholesterol, nonesterified fatty acids, and glucose were determined for 9 months (September, 1972, to May, 1973) in 19 fasting horses and ponies (8 Morgan horses, 7 Thoroughbred horses, and 4 Shetland Ponies). Morgan horses had higher concentrations of total lipid than did Thoroughbreds, although the relative proportions of each type of lipid were similar in the 2 breeds. Shetland Ponies had higher nonesterified fatty acid and lower glucose concentrations than did either breed of horse. In both breeds of horses, concentrations of serum triglycerides in the cold months (December to March) were lower than those in the warm months. In the Shetland Pony, there was no seasonal variation in triglycerides, but a significant increase was seen in concentration of nonesterified fatty acids in the cold months. The significance of these findings is discussed.     

Acute experimentally induced aflatoxicosis in the weanling pony

Nineteen weanling ponies and 1 adult pony were given a single oral dose of aflatoxin B1 (AFB1). Dosages were: 0, 0.5, 1, 2, 4, 5, 6, and 7.4 mg of AFB1/kg of body weight. Vital signs were monitored, and whole blood and serum collected for analysis of serum enzymes, prothrombin time, blood cell counts, and serum urea nitrogen. Ponies that died were examined for gross lesions, and tissues were collected for histopathologic examination and analysis of AFB1 and AFM1 residues. Two of the 4 ponies given the 2 mg/kg dose and all ponies given the larger dosages died within 76 hours. Clinical signs included increased rectal temperature, faster heart and respiratory rates, abdominal straining, bloody feces, and tetanic convulsions. At necropsy, ponies that died of acute aflatoxicosis showed visceral petechiae and hepatic focal lesions. Histopathologic changes included severe hepatic necrosis, vacuolation, and bile duct hyperplasia. Aflatoxins B1 and M1 were recovered from liver, kidney, skeletal muscle, and gastrointestinal contents. One other pony given the 2 mg/kg dose died 32 days after dosing, and 1 control pony died after 70 days. Continuous elevations in prothrombin time and serum aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyl transpeptidase levels were observed in ponies dosed at 4 mg/kg or more. Significant (P less than 0.05) elevations in these values, which peaked 2 to 3 days after dosing, were seen in ponies given the 2 mg/kg dose. This group also had significant increases over controls in PCV and hemoglobin concentration 5 days after dosing.     

A Preliminary Comparison of Lidocaine and Xylazine as Epidural Analgesics in Ponies

Xylazine (0.35 mg/kg) or lidocaine (0.35 mg/kg) was injected into the epidural space of six ponies to compare their effectiveness as epidural analgesics. Each pony received both treatments at 1 week intervals with the order of treatments randomized. Xylazine produced analgesia of significantly longer duration (247 +/- 58 minutes) than that produced by an equal dose of lidocaine (135 +/- 22 minutes). Mild transient ataxia of no clinical significance developed in all ponies with both treatments. Spinal cords were removed from two ponies and examined histologically. No discernible pathologic changes were noted.     

Experimental Coxofemoral Replacement Hemiarthroplasty in the Pony

For the in vivo evaluation of hip joint prostheses that are developed for man, the suitability of the pony as an animal model has been studied. Human and custom made prostheses were implanted into 1 femur in each of 7 ponies to replace the femoral head. The surgical approach was through a caudolateral incision. The prosthesis was fixed in the femur with bone cement. Because of errors in the implantation technique and resulting lack of sufficient fixation 2 ponies as well as 1 control animal with an excision arthroplasty were unwilling or unable to stand. Rigid fixation of the implant was achieved in 3 ponies. They were returned to pasture after 8 days. A full return to a normal gait did not occur within an observation period of up to 3 months. All 3 ponies developed a dorsolateral coxofemoral luxation and pseudarthrosis within the first 10 days. A mismatch between the equine anatomy and human prosthesis geometry was thought to be the cause. We, therefore, believe that the pony does not provide a suitable model for the testing of human femoral joint implants. The results, however, indicate that coxofemoral surgery can be performed in the adult pony. For clinical reconstruction of joint function, a custom made total artificial hip joint might provide better results.     

Electroencephalographic Responses to a Noxious Surgical Stimulus in Mules,Horses, and Ponies

The aim of this study was to investigate the electroencephalographic (EEG) response of equidae to a castration stimulus. Study 1 included 11 mules (2½–8 years; 230–315 kg) and 11 horses (1½–3½ years; 315–480 kg); study 2 included four ponies (15–17 months; 176–229 kg). They were castrated under halothane anesthesia after acepromazine premedication (IV [study 1] and intramuscular [study 2]) and thiopental anesthetic induction. Animals were castrated using a semiclosed technique (study 1) and a closed technique (study 2). Raw EEG data were analyzed and the EEG variables, median frequency (F50), total power (Ptot), and spectral edge frequency (F95), were derived using standard techniques at skin incision (skin) and emasculation (emasc) time points. Baseline values of F50, Ptot, and F95 for each animal were used to calculate percentage change from baseline at skin incision and emasculation. Differences were observed in Ptot and F50 data between hemispheres in horses but not mules (study 1) and in one pony (study 2). A response to castration (>10% change relative to baseline) was observed in eight horses (73% of animals) and four mules (36% of animals) for F50 and nine horses (82%) and four mules (36%) for Ptot. No changes in F95 data were observed in any animal in study 1. Responses to castration were observed in three ponies (75% of animals) for F50, one pony (25%) for F95, and all ponies for Ptot. Alteration of acepromazine administration and castration technique produced a protocol that identified changes in EEG frequency and power in response to castration.     

Phenolsulfonphthalein pharmacokinetics and renal morphologic changes in adult pony mares with gentamicin-induced nephrotoxicosis

Changes in renal function, determined by pharmacokinetics of phenolsulfonphthalein (PSP), and renal morphologic features were examined in adult pony mares given 20 mg of gentamicin sulfate/kg of body weight, IV, q 8 h (group A) n = 7 or isotonic saline solution, IV, q 8 h, n = 5 (group B) for 14 days. Susceptibility of ponies to gentamicin-induced nephrotoxicosis was varied. Two group-A ponies developed acute renal failure and were euthanatized before treatment day 14, whereas 5 group-A A ponies did not develop physical or behavioral abnormalities after 14 days of gentamicin administration. All group-A ponies but none of group-B ponies developed ultrastructural abnormalities of the proximal tubular epithelium, consistent with gentamicin-induced nephrotoxicosis. Significant (P less than 0.05) differences were not detected in pharmacokinetic values of either group. Clearance of PSP was reduced in 4 group-A ponies that developed the most severe gentamicin-induced nephrotoxicosis. Changes in clearance of PSP were significantly (P less than 0.05) correlated with changes in the serum creatinine concentration.     

Urinary concentration of corticoids in ponies with hyperlipoproteinaemia or hyperadrenocorticism

The urinary corticoid:creatinine (c:c) ratio was determined in ten pony mares suffering from hyperlipoproteinaemia. The mean (+/- sd) urinary c:c ratio of these ten ponies (47 +/- 31 x 10(-6)) was not significantly different from that of twelve pony mares with a pituitary pars intermedia adenoma (31 +/- 18 x 10(-6). The correlation between the urinary concentration of corticoids and plasma total lipids, and the correlation between the urinary c:c ratio and plasma total lipids in ponies with hyperlipoproteinaemia were not significant (P > 0.05; r = 0.53 and r = 0.008, respectively). Preliminary results favour primary hyperadrenocorticism being associated with hyperlipoproteinaemia. In conclusion, the data presented here suggest that cortisol can contribute to insulin resistance in ponies with hyperlipoproteinaemia.     

Incidence of polysaccharide storage myopathy: necropsy study of 225 horses

Muscle samples were obtained at necropsy from 225 horses and ponies 1 year of age or older. Samples were processed in routine manner and were stained with hematoxylin and eosin and with periodic acid-Schiff for glycogen. Sections were examined for abnormal glycogen content and amylase-resistant complex polysaccharide and for chronic myopathic change (excessive fiber size variation, increase in number of internal nuclei). A total of 101 horses and ponies with lesions of polysaccharide storage myopathy were identified. Age of affected horses ranged from one to 30 years, with a mean of 14.7 years. Mean age of nonaffected horses was 12 years. Incidence of polysaccharide storage myopathy varied depending on breed; Thoroughbreds had the lowest (27%) and draft-related horses had the highest (86%) incidence. Chronic myopathic changes were more severe in polysaccharide storage myopathy-affected horses than in nonaffected horses. Results of this study indicate that polysaccharide storage myopathy is a common disorder of many breeds of horses and ponies.     

Suppression of the pathogenic effects of Strongylus edentatus larvae with thiabendazole.

Four pony foals were inoculated with Strongylus edentatus infective larvae and on days 3 and 4 postinfection two of the ponies were treated with thiabendazole, each at the rate of 440 mg/kg of body weight. Total circulating eosinophil counts in untreated ponies increased to over 1700 per cu mm after the second week postinfection. In the treated ponies as well as in an uninfected untreated pony eosinophil counts did not increase beyond 100 per cu mm. At necropsy on day 35 postinfection the cecum, colon and omentum of treated ponies were normal and few tracks were present on the surface of the liver. In untreated ponies nodules were observed on the serosal surface of the cecum and right ventral colon and white foci and tracks were numerous on the surface of the liver. A total of 53 fourth stage larvac was recovered from the livers of the thiabendazole treated ponies and 1194 from the untreated ones.