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Topic:Pony
Ponies are members of the Equidae family and share many physiological and anatomical characteristics, yet they are distinguished by several key differences. Ponies are generally smaller in stature, with a height at the withers of 14.2 hands (58 inches) or less, while horses exceed this height. In addition to size, ponies often exhibit a stockier build, thicker manes, tails, and coats, and a greater bone density compared to horses. These differences can influence their suitability for various tasks and environments. This topic encompasses a collection of peer-reviewed research studies and scholarly articles that explore the genetic, phenotypic, and behavioral distinctions between ponies and horses, as well as their implications for breeding, management, and performance in equine disciplines.
Effects of increased end-expiratory lung volume on breathing in awake ponies. We studied the changes in breathing and respiratory muscle electromyograms (EMG) during passively induced increases in end-expiratory lung volume (EELV) in awake normal (N), hilar nerve-denervated (HND), carotid body-denervated (CBD), and HND + CBD ponies. EELV was increased by applying continuous negative pressure (-10 and -20 cmH2O) around the torso of the standing pony. In all groups, negative pressure produced sustained increases in EELV that were linearly related to the degree of negative pressure. Elevated EELV decreased breathing frequency (f) in N and CBD ponies but increased f in HND ...
Effect of increased inspired CO2 on respiratory dead space in ponies. The objective of the present study was to determine the effect of elevated inspired CO2 on respiratory dead space (VD) of 12 normal, 8 carotid body-denervated (CBD), 7 hilar nerve-denervated (HND), and 6 CBD+HND ponies. The Fowler technique was used to determine VD on a breath-by-breath basis while the ponies breathed room air and inspired CO2 at 3 and 6%. During room air breathing, tidal volume (VT) and VD were greater in HND ponies than in normal and CBD ponies (P less than 0.05), and VT was less and VD/VT was greater after CBD than before CBD. For all groups. VD, VT, and breathing frequency...
Myocardial blood flow, metabolism, and function with repeated brief coronary occlusions in conscious ponies. Studies were performed in the conscious pony instrumented with a Doppler flow probe and hydraulic occluder on the left anterior descending coronary artery (LAD), sonomicrometry crystals and intraventricular micromanometer in the left ventricle, and catheters in the left atrium and anterior interventricular vein. Two-minute LAD occlusions were performed every 30 min continuously or during working hours. Data on release of catabolites (potassium, hydrogen ions, and lactate) and norepinephrine from the initially dysfunctional region were obtained periodically during a regimen of 445 +/- 56 occlus...
Production of 5 alpha-dihydroprogesterone during late pregnancy in the mare. Changes in the progesterone metabolite 5 alpha-dihydroprogesterone (5 alpha-DHP) in maternal plasma in late gestation, and possible sites of production of this steroid were studied in pony and Thoroughbred mares by an enzyme-linked immunosorbant assay for 5 alpha-DHP. In Thoroughbred mares, plasma 5 alpha-DHP increased from 63.7 +/- 10.5 ng/ml (27 days pre-partum) to 161.7 +/- 30.8 ng/ml (1 day pre-partum) falling to 90.2 +/- 16.1 ng/ml on the day of parturition. In pony mares, values rose from 30.8 +/- 8.1 ng/ml (27 days pre-partum) to 79.1 +/- 30.8 ng/ml (3 days pre-partum) and then decrease...
Triglyceride, insulin, and cortisol responses of ponies to fasting and dexamethasone administration. Ponies were evaluated for their response to feed withholding and exogenous administration of corticosteroids (dexamethasone 0.04 mg/kg intramuscular [IM]) in an attempt to reproduce the hyperlipemia syndrome. Because insulin resistance has been associated with hyperlipemia, all ponies were initially evaluated for insulin response to an oral glucose load and normal dexamethasone suppression of serum cortisol. Four ponies were identified as hyperinsulinemic reflecting insulin resistance. All ponies had suppressed cortisol concentrations following dexamethasone administration. Feed withdrawal res...
Prolactin secretion in lactating mares before and after treatment with bromocriptine. The effect of treating lactating mares with the dopamine agonist bromocriptine was investigated. Seven pony and 4 Thoroughbred lactating mares were given a single intramuscular (i.m.) injection of 100 mg bromocriptine between Days 18 and 28 after foaling when the secretion rate of prolactin was elevated. Prolactin and luteinizing hormone (LH) concentrations were measured in serial peripheral plasma samples taken before and after the treatment and, in 5 of the pony mares, levels of these hormones were also measured in pituitary venous effluent obtained by cannulation of the cavernous sinus. In ...
The effects of continuous treatment of stallions with high levels of a potent GnRH analogue. The effect of long-term treatment of stallions with a powerful gonadotrophin-releasing hormone (GnRH) analogue was investigated. In the first part of the study, 9 sexually mature pony stallions were allocated to 1 of 3 groups, each of which was treated with 240 micrograms or 60 micrograms Buserelin per day administered by subcutaneously sited osmotic pumps or 30-50 micrograms Buserelin per day via solid, slow-release implants injected subcutaneously. Peripheral blood plasma and serum samples were collected frequently and assayed for follicle-stimulating hormone (FSH) and luteinizing hormone (L...
Metabolic changes in thoroughbred and pony foals during the first 24 h post partum. Metabolic rates, rectal temperatures and respiratory quotients (RQ) were determined during the first 24 h post partum in Thoroughbred and pony foals and in relation to environmental temperature. Both breeds had high metabolic rates (greater than 200 W/m2) during the first hour post partum when they were wet and shivering; by 4 to 24 h values were fairly steady at about 153 and 105 W/m2 for Thoroughbred and pony foals, respectively. At birth, rectal temperature was lower in Thoroughbred foals than in pony foals; values increased during the first hour, and then decreased. At 24 h of age, both br...
Effect of interval between doses on response of the pony to sodium bicarbonate. Three pony geldings were given sodium bicarbonate orally in order to study the effect on blood pH and bicarbonate and to determine if frequency of dosing influences the response. In a preliminary study, it appeared that a carry-over effect might occur if the interval between dosing was only 2 days. The ponies received 2 doses of sodium bicarbonate (400 mg/kg) 7 days apart in trial one and then in trial two they received 2 doses of sodium bicarbonate 4 days apart. The sodium bicarbonate was mixed with 2 liters of warm water and given through a nasogastric tube on each trial day. Blood samples w...
Effect of constant light exposure on circulating gonadotrophin levels and hypothalamic gonadotrophin-releasing hormone (GnRH) content in the ovariectomized pony mare. Melatonin is thought to play a role in relaying photic information to the central nervous system as part of the seasonal reproductive cycle of the mare. However, the mechanisms by which melatonin may act are unknown. Therefore, this study was designed to determine whether exposure to constant light would, by reducing circulating melatonin concentrations, have any effect on hypothalamic gonadotrophin-releasing hormone (GnRH) content and circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Blood samples were collected for 12 h at 15-min intervals from 8 ovariect...
Paneth cell degranulation and lysozyme secretion during acute equine alimentary laminitis. The equine Paneth cell response to a shift in the microbial balance of the intestinal tract was studied by inducing an acute episode of alimentary laminitis in 6 mature ponies. The normal bacterial population of the gut was modified by administration of a carbohydrate-rich ration. During acute laminitis a dramatic degranulation of the Paneth cells occurred in the intestinal glands throughout the duodenum, jejunum, and ileum. Bacteriocidal lysozyme, which was immunohistochemically identified as a component of the Paneth cell secretory granule, was evident in the glandular lumina and in degranul...
Squamous cell carcinoma of the equine external genitalia: a review and assessment of penile amputation and urethrostomy as a surgical treatment. A retrospective analysis was performed on 48 cases of suspected neoplasia involving the equine external genitalia. Forty nine squamous cell carcinomata (SCC) and 23 squamous papillomata (SP) were identified. Two cases of epithelial hyperplasia and one case of habronemiasis were also recognised histopathologically. The glans penis was the most common site of tumour development accounting for 53 per cent of cases of SCC and 61 per cent of SP. The urethral diverticulum, urethral process or urethra was involved in 27.6 per cent (8/29) of cases of SCC. Twelve per cent (5/41) of cases of SCC were co...
Intra-follicular and peripheral steroid characteristics during vernal transition in the pony mare. This experiment investigated steroid production by ovarian tissues, in vitro, of pony mares during vernal transition from anoestrus to the breeding season. Follicular dynamics were monitored to detect the first, second, third or fourth transition follicle, greater than or equal to 30 mm diameter or the first large post luteal follicle of the breeding season. Twenty-four hours after a large follicle was detected, theca (T) and granulosa (G) tissues were harvested. Separate and co-incubations of these tissues were conducted to determine steroid production in early transition (ET), late transitio...
Effect of oral melatonin treatment on the seasonal physiology of pony stallions. This study tested the role of melatonin in the regulation of seasonal physiological change in the pony stallion. Four 3-year-old, Welsh Mountain pony stallions were housed initially under the prevailing short-day photoperiod in December (8 of light [L]:16 h of darkness [D]) before being transferred to long days (16L:8D) on 13 January for the remaining 22 weeks of the study. On Day 76 (11 weeks later) the stallions began an 11-week period of daily melatonin treatment (20 mg orally, 8 h after lights on). Marked changes in mean plasma testosterone, beta-endorphin and cortisol concentrations occur...
Effects of furosemide on ponies with recurrent airway obstruction. The effect of aerosol and intravenous administrations of furosemide was examined in ponies with recurrent obstructive pulmonary disease, commonly called 'heaves'. This recurrent airway disease bears many similarities to human asthma. Six ponies with the disease (principal animals) were studied during clinical remission and during an acute attack of airway obstruction precipitated by stabling and feeding dusty hay. Six control animals were also studied. Furosemide (1.0 mg/kg) or vehicle was administered by aerosol in the first study, and intravenously in a second study. In principal ponies with...
Attenuated Hering-Breuer inflation reflex 4 years after pulmonary vagal denervation in ponies. The purpose of this study was to determine whether there was any recovery of the Hering-Breuer inflation reflex in ponies between 2-4 wk and 3-4 yr after hilar nerve denervation (HND). Under anesthesia and before HND, airway occlusion after a 3-liter lung inflation lengthened the subsequent occluded breath by nearly 10 times the control breath duration. Between 2 wk and 3-4 yr after HND, this maneuver increased the duration of the occluded breath by only 2.5 times the control breath duration. Also under anesthesia, the airway was occluded at end expiration. This maneuver increased the duration...
Cardiorespiratory responses to electrical stimulation of the buccal mucosa in ponies. The cardiovascular and respiratory responses to electrical stimulation of the buccal mucosa under general anaesthesia in ponies were measured in order to provide some insight into the cardiorespiratory effects of anaesthesia in equidae. This knowledge may be useful for reducing morbidity during clinical anaesthesia in horses. Anaesthesia was induced with intravenous thiopentone and maintained with 1.3 per cent inspired halothane in oxygen. Arterial blood pressure, heart rate, minute volume, tidal volume, respiratory rate, arterial blood gas tensions and clinical signs of anaesthetic depth were...
Morphologic and ultrastructural evaluation of effect of ischemia and dimethyl sulfoxide on equine jejunum. Morphologic changes in equine jejunal segments subjected to 1 hour of ischemia and 1 hour of reperfusion, and protective effects of systemic administration of dimethyl sulfoxide (DMSO; 1 g/kg of body weight) were investigated in 18 ponies, using light microscopy and scanning and transmission electron microscopy. Ponies were allotted to 4 groups: group 1--control (n = 3); group 2--DMSO (n = 3); group 3--ischemia (n = 6); and group 4--ischemia and DMSO (n = 6). In each pony, 2 jejunal sections were evaluated. The first section was obtained prior to induction of ischemia, and the second was obtai...
Condylar buttress plate fixation of femoral fracture in a colt. A Salter-Harris type-II fracture of the distal portion of the femur in a 1-year-old Pony of America was repaired by use of lateral plating combined with interfragmentary compression. The configuration of the fracture and the method of internal fixation with a condylar buttress plate were unique and resulted in primary bone healing, seen at the 5-month follow-up examination.
Effect of partial spinal cord ablation on exercise hyperpnea in ponies. We addressed the role of spinal afferent information in the exercise hyperpnea. Arterial PCO2 (PaCO2) was assessed in 10 normal ponies during low (1.8 mph 7% or 17% grade) or moderate (6 mph 7% grade) treadmill exercise. After control studies, bilateral spinal ablation (SA) of the dorsolateral sulcus and dorsolateral funiculus at L2 was performed in seven ponies. In normal ponies within the first 90 s of exercise, PaCO2 initially decreased 2.7, 4.1, and 5.2 Torr below rest at the three work loads, respectively (P less than 0.05). PaCO2 thereafter increased toward resting levels but remained 1....
Intra-osseous pressure and pressure pulse gradients along the equine third metatarsal bone. Intra-osseous pressure measurements in the third metatarsal bone of anesthetised young and mature ponies demonstrated that a pressure gradient exists along the bone, the pressure being highest at the level of the nutrient foramen and decreasing distally and proximally from this point. The height of the intra-osseous pressure pulse also decreased toward the bone ends. It is concluded that the sites of measurement of the intra-osseous pressure in clinical and experimental studies should be standardized.
Diaphragm does not produce ammonia or lactate during high-intensity short-term exercise. To ascertain whether costal diaphragm engages in ammonia and lactate production (like limb muscles) during high-intensity short-term exercise, experiments were carried out on six healthy trained ponies in which phrenic venous catheters had been implanted 5-9 days earlier. Simultaneous anaerobically obtained blood samples from abdominal aorta and the phrenic vein at rest and during 4 min of exertion at 32 km/h and at a 7% grade were analyzed for blood-gas variables as well as lactate and ammonia concentrations using standard procedures. At rest, heart rate was 47 +/- 4 beats/min and the diaphra...
Two rare cutaneous neoplasms in horses: apocrine gland adenocarcinoma and carcinosarcoma. Two rare equine cutaneous neoplasms, an apocrine gland adenocarcinoma and a carcinosarcoma were diagnosed in a 17-year-old pony and a 14-year-old mare, respectively. The apocrine gland adenocarcinoma was present on the prepuce. Histologically, papillary projections of low cuboidal to columnar epithelial cells were generally well differentiated, and surrounded dilated acini. Stromal invasion was present, but vascular and lymphatic invasion was not seen. The carcinosarcoma was present in the right flank of the mare. Two discrete cell populations were characterized histologically. One portion of ...
Production of interleukin 2 and expression of interleukin 2 receptors by pony peripheral blood lymphocytes after stimulation with a soluble fraction of Trypanosoma evansi. Pony peripheral blood lymphocytes (PBL) were stimulated with a soluble fraction of Trypanosoma (T.) evansi (SF). As determined by 3H-thymidine incorporation, the cells underwent a proliferative response and were able to: a) produce a factor having the biological activities of interleukin 2 (IL-2) since their supernatants could support the in vitro growth of pony PBL stimulated with concanavalin A (Con A-blasts); b) undergo a further proliferative response when incubated in short term cultures with SF, human recombinant IL-2 (hrIL-2), or both c) bind specifically radiolabelled hrIL-2 (125I-hrIL...
Tonometric and tonographic studies in the normal pony eye. Tonometric and tonographic techniques were evaluated in the normal pony and compared to other species. Applanation tonometry was utilised to calculate the ocular ridigity of the normal equine eye. The mean intraocular pressure for the pony eye was established as 23.5 mm Hg (sd +/- 4.5). Comparing the non-anaesthetised and anaesthetised pony eye (xylazine-ketamine and glycerol guaiacolate) no significant change in intraocular pressure occurred (P < 0.49). Mean aqueous outflow facility was 0.88 microliter/min/mm Hg (sd +/- 0.65) which is significantly higher (P < 0.01) than the canine and ...
Effect of low-dose butorphanol on halothane minimum alveolar concentration in ponies. Minimum alveolar concentration (MAC) for halothane was measured before and after administration of intravenous butorphanol (0.022 and 0.044 mg/kg in bodyweight in nine yearling Shetland ponies. Arterial blood pressure, heart rate, respiratory rate, expired CO2 and rectal temperature was also measured. Even though mean MAC values decreased 10 and 9 per cent after the low and high doses respectively, they were not statistically different from those measured prior to butorphanol. Halothane MAC values increased after butorphanol in two ponies, both animals increasing locomotor activity and demonst...
Effect of acute acidemia on blood biochemical variables in healthy ponies. L-Lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only...
