Omneity® Pellets
All-In-One Vitamin & Mineral Pellet
Topic:Physiology
The physiology of horses encompasses the study of the biological functions and processes that occur within the equine body. This includes the examination of various systems such as the cardiovascular, respiratory, musculoskeletal, digestive, and nervous systems. Understanding equine physiology is essential for comprehending how horses adapt to different environmental conditions, perform physical activities, and respond to health challenges. Research in this field often focuses on the mechanisms of energy metabolism, thermoregulation, and muscle function during exercise, as well as the physiological responses to stress and disease. This page compiles peer-reviewed research studies and scholarly articles that explore the diverse aspects of equine physiology, providing insights into the biological processes that support the health and performance of horses.
Effect of multiple denervations on the exercise hyperpnea in awake ponies. In three previously reported studies, we had documented that the normal exercise hyperventilation in ponies is accentuated by carotid body denervation (CBD), not affected by hilar nerve pulmonary vagal denervation (HND), and mildly attenuated by spinal cord ablation of the dorsal lateral columns at L2 (SA). In the present study, we hypothesized that if redundancy of control existed in exercising ponies, then multiple denervations of theoretically important pathways in the same animal might attenuate the ventilatory response to exercise in a way not predictable by the individual lesion experime...
Serotonin-containing cells in the horse gastrointestinal tract. The presence and distribution of serotonin-containing cells in the gastroenteric tract of horses have been investigated. The enterochromaffin (EC) cells have been identified using immunostaining procedures at both light and electron microscopic level. The EC cells were very numerous in the pyloric gland region, were only few in the duodenum but were absolutely lacking from the more distal portions of the intestine.
A lectin histochemical study of gustatory (von Ebner’s) glands of the horse tongue. In the present work, gustatory glands (von Ebner's glands) of the horse tongue were examined by means of five peroxidase-conjugated lectins (PNA, DBA, SBA, UEA I, WGA), with and without prior sialidase digestion, in order to investigate the presence and distribution of carbohydrate residues in secretory cells and duct cells. The most intense staining of secretory cells was observed with PNA after pre-treatment with neuraminidase. This indicates that the terminal trisaccharide sequence sialic acid- (alpha 2-->3, 6) galactosyl (beta 1-->3) N-acetylgalactosamine is the most frequent oligosa...
Mural blood flow distribution in the large colon of horses during low-flow ischemia and reperfusion. Six horses were subjected to 3 hours of low-flow ischemia and 3 hours of reperfusion of the large colon. After induction of anesthesia, the large colon was exteriorized through a ventral midline celiotomy. Colonic blood flow was measured continuously, using Doppler ultrasonic flow probes placed on the colonic arteries supplying the dorsal and ventral colons and was allowed to stabilize for 15 to 30 minutes after instrumentation. Low-flow ischemia was induced by reducing colonic arterial blood flow to 20% of baseline (BL) flow. Colonic mucosal, seromuscular, and full-thickness blood flow were d...
Effect of enzymes on the growth of human and animal rotaviruses. The growth of group A human, bovine, equine and porcine rotaviruses were enhanced by pretreatment of virus with pancreatin, trypsin, protease, alkaline phosphatase or pepsin and incorporation of these enzymes in maintenance medium. In contrast, alpha-amylase or lipase inhibited the growth of equine and porcine rotaviruses. The other enzymes, adenosine deaminase, lactase, lysozyme, ribonuclease or triose-phosphate isomerase gave little or no change in the growth of all four rotaviruses.
A non-invasive and quantitative method for the study of tissue injury caused by intramuscular injection of drugs in horses. The present study was undertaken to measure the weight of muscle destroyed by an intramuscular injection of phenylbutazone (PBZ) in horses. In six horses, CK disposition parameters were evaluated after intravenous (i.v.) and intramuscular (i.m.) administration of a CK horse preparation. The same horses received PBZ, a potentially irritating agent, by i.v. and i.m. (neck and hindquarter) routes. Data were analysed using compartmental approaches and instantaneous CK flux was calculated using a discrete deconvolution method. For a 150 U/kg CK dose, the steady-state volume of distribution was 0.05...
Hypoxic helium breathing does not reduce alveolar-arterial PO2 difference in the horse. In a previous study we evaluated the mechanism of alveolar-arterial PO2 (AaPO2) reduction when nitrogen is replaced with helium in normoxia (FIO2 = 0.21). The reduction in AaPO2 was not due to changes in VA/Q inequality, pulmonary O2 diffusing capacity, or cardiac output, but to more complete diffusion equilibration as a consequence of the higher ventilation and thus PAO2 (which reduced the average slope of the hemoglobin O2 dissociation curve (ODC), and thus enhanced diffusive equilibration). We hypothesized that hypoxic He/O2 breathing in contrast would not reduce the AaPO2 because PAO2 and ...
Blood parameter and heart rate response to training in Andalusian horses. A study was performed on Andalusian horses in order to assess the response of heart rate and various blood parameters to training. Two tests were performed, at two and four months of training respectively. Exercise schedules were of increasing intensity, over a distance of 1000 meters. Speed was progressively increased, from 4 m/s to 8.5 m/s, over four exercise stages. In both tests, a recovery period of 5 min followed each stage. Sample collection (by puncture of the external jugular vein) was performed with the animals at rest, within the first minute after each exercise stage, and at 10, 15...
Local initiation of spermatogenesis in the horse. Gross observation of testicular parenchyma of 1.5- to 2-yr-old horses reveals both light and dark regions. If this gross, differential shading reflects quantitative differences in the development of spermatogenesis and interstitial cell populations, the horse may prove to be a useful model for study of the paracrine relationships associated with initiation of spermatogenesis. The objective of this study was to characterize seminiferous tubules and interstitium of testes with gross, differential shading. Testes with both light and dark regions of parenchyma were obtained from horses 1.5-2 yr ol...
Electrocardiographic values in Spanish-bred horses of different ages. The duration of electrocardiograph wave forms and intervals were determined in 179 Spanish-bred (Andalusian) horses aged from 1 month to 17 years. The values were compared with those of other breeds, and the relationship between electrocardiographic data and age was examined. High correlation coefficients were found between PR, ST and QT intervals and the age of the horses, and an inverted relation between heart rate and age was found. A multiple range analysis was made and the results suggest that significant changes in duration values and heart rate occurred at the age of 6 months and in the...
Kinetics, dose response, tachyphylaxis and cross-tachyphylaxis of vascular leakage induced by endotoxin, zymosan-activated plasma and platelet-activating factor in the horse. Vascular leakage induced by intradermal injection of endotoxin, zymosan-activated plasma (ZAP) and platelet-activating factor (PAF) was measured in nine Thoroughbreds using 125-iodine human serum albumin (125I-HSA) as a marker in the blood. ZAP and PAF produced dose-dependent increases in vascular permeability with the maximum occurring within the first 15 min after injection. The vascular leakage induced by endotoxin was also dose-dependent, but the maximum occurred 2 h after intradermal injection. Intradermal sites previously injected with endotoxin were refractory to a second injection of e...
Response to demineralized bone matrix implantation in foals and adult horses. Equine demineralized bone matrix, particle size 2 to 4 mm, was implanted SC and IM in 4 foals and 4 adult horses. The implants were removed between 5 and 8 weeks after implantation. Bone formation was induced by SC and IM implantations in all animals. The implantation site had a marked effect on the amount of bone that developed, bone being formed earlier and in greater amounts when the matrix was implanted IM. The amount of bone formed increased with increasing time after matrix implantation at both sites. Demineralized bone matrix implantation also led to formation of small amounts of chondr...
Effect of phenytoin on skeletal muscle from quarter horses with hyperkalaemic periodic paralysis. The contractile activity, the threshold for calcium-induced calcium release in fractions of sarcoplasmic reticulum and the potassium concentration were determined in preparations of semimembranosus muscle from normal quarter horses and quarter horses with hyperkalaemic periodic paralysis before and after they were treated with phenytoin. Before the treatment there was no difference in caffeine contracture or electrically elicited twitch response between the two groups. For one week after the treatment, the time to peak tension of caffeine contractures was significantly (P < 0.005) reduced i...
Stability of penicillin G, ampicillin, amikacin and oxytetracycline and their interactions with food in in vitro simulated equine gastrointestinal contents. Penicillin G was extensively (84.7 per cent) and amikacin moderately (14.4 per cent) degraded when incubated for one hour in a chloride buffer at pH 1.9 designed to mimic the equine gastric pH. Ampicillin and oxytetracycline were stable at pH 1.9. Penicillin and ampicillin were moderately stable (more than 90 per cent) when incubated in equine caecal liquor for three hours but were degraded by about 65 per cent after 24 hours. More than 80 per cent of the initial concentrations of amikacin and oxytetracycline were recovered after 24 hours' incubation in equine caecal liquor. The concentrations...
Dietary protein and(or) energy restriction in mares: plasma growth hormone, IGF-I, prolactin, cortisol, and thyroid hormone responses to feeding, glucose, and epinephrine. Sixteen light horse mares were fed diets of bermudagrass hay and a corn/cottonseed hull-based supplement formulated to contain either 100% (control) or 50% (restricted) of the protein and(or) energy requirements for maintenance in a 2 x 2 factorial arrangement of treatments. Plasma IGF-I, prolactin, cortisol, triiodothyronine, and thyroxine were monitored for 33 d. On the 27th d, frequent blood samples were drawn throughout the day for the measurement of growth hormone (GH), and on the 29th d, an epinephrine challenge and an i.v. glucose tolerance test (IVGTT) were performed in the morning and...
Age related changes in biochemical markers of bone metabolism in horses. Biochemical markers of bone metabolism were analysed in serum samples obtained from 60 horses with no history of orthopaedic disease (age 3 months-20 years). Serum levels of the carboxyterminal propeptide of type I procollagen (PICP), a marker of bone formation and the pyridinoline cross linked telopeptide domain of type I collagen (ICTP), a putative marker of bone resorption, were measured by radioimmunoassay (RIA). Serum levels of the bone specific isoenzyme of alkaline phosphatase (BALP), another marker of bone formation, were measured by a wheatgerm agglutinin affinity (WGA) method. Total ...
Microvascular permeability and endothelial cell morphology associated with low-flow ischemia/reperfusion injury in the equine jejunum. Microvascular permeability of the jejunum of clinically normal equids and microvascular permeability associated with 60 minutes of ischemia (25% baseline blood flow) and subsequent reperfusion were investigated. Eight adult horses were randomly allotted to 2 equal groups: normal and ischemic/reperfusion injury. Lymphatic flow rates, mesenteric blood flow, and lymph and plasma protein concentrations were determined at 15-minute intervals throughout the study. Microvascular permeability was determined by estimates of the osmotic reflection coefficient, which was determined when the ratio of lymp...
Systemic and colonic venous plasma eicosanoid and endotoxin concentrations, and colonic venous serum tumor necrosis factor and interleukin-6 activities in horses during low-flow ischemia and reperfusion of the large colon. Twenty-four horses were randomly allocated to 3 groups. Horses were anesthetized, subjected to a ventral midline celiotomy, and the large colon was exteriorized and instrumented. Group-1 horses served as sham-operated controls. Group-2 horses were subjected to 6 hours of low-flow colonic arterial ischemia, and group-3 horses were subjected to 3 hours of ischemia and 3 hours of reperfusion. Baseline (BL) samples were collected, then low-flow ischemia was induced by reducing ventral colonic arterial blood flow to 20% of BL. All horses were monitored for 6 hours after BL data were collected. Bloo...
Selection of follicles, preculture oocyte evaluation, and duration of culture for in vitro maturation of equine oocytes. Equine oocytes (n = 537) were collected from slaughterhouse ovaries (n = 118 mares) by scraping the internal follicular wall. Preculture record was made of the appearance of oocyte investments (no cumulus, corona radiata only, compact cumulus, expanded cumulus), appearance of cytoplasm (homogeneous, condensed heterogeneous/fragmented), and nuclear maturation stages (germinal vesicle, germinal-vesicle breakdown, metaphase I, metaphase II, degenerated). There was no difference between follicles > 30 mm and follicles < or = 30 mm in the preculture frequency distribution among the 5 nuclear stages...
Sodium channel inactivation is impaired in equine hyperkalemic periodic paralysis. 1. Equine hyperkalemic periodic paralysis (E-HPP) is a dominantly inherited disorder of muscle that causes recurrent episodes of stiffness (myotonia) and weakness in association with elevated serum K+. Affected horses carry a mutant allele of the skeletal muscle isoform of the Na channel alpha-subunit. To understand how this mutation may cause the disease phenotype, the functional defect in Na channel behavior was defined physiologically by recording unitary currents from cell-attached patches on normal and affected equine myotubes. 2. The presence of the mutation was confirmed in our cell lin...
Systemic and colonic venous hemostatic alterations in horses during low-flow ischemia and reperfusion of the large colon. Twenty-four horses were randomly allocated to 3 groups. All horses underwent a ventral midline celiotomy, and the large colon was exteriorized and instrumented. Group-1 horses served as sham-operated controls, group-2 horses underwent 6 hours of colonic ischemia, and group-3 horses were subjected to 3 hours of ischemia and 3 hours of reperfusion. Baseline blood samples were collected, then low-flow colonic ischemia was induced in horses of groups 2 and 3 by reducing colonic arterial blood flow to 20% of baseline. All horses were monitored for 6 hours. Citrated systemic venous (SV) blood sample...
Tropane alkaloids and toxicity of Convolvulus arvensis. Horses in a few, localized northern Colorado pastures exhibited weight loss and colic. At post mortem, intestinal fibrosis and vascular sclerosis of the small intestine was identified. The pastures where the affected horses grazed were overrun by field bindweed (Convolvulus arvensis). Bindweed from the pasture was found to contain the tropane alkaloids tropine, pseudotropine, and tropinone and the pyrrolidine alkaloids cuscohygrine and hygrine. Laboratory mice readily ate C. arvensis and exhibited a variety of abnormal clinical signs depending on the amount eaten. Similar alkaloids have been f...
Effects of dimethyl sulfoxide, allopurinol, 21-aminosteroid U-74389G, and manganese chloride on low-flow ischemia and reperfusion of the large colon in horses. Thirty horses were randomly assigned to 1 of 5 groups. All horses were anesthetized and subjected to ventral midline celiotomy, then the large colon was exteriorized and instrumented. Colonic arterial blood flow was reduced to 20% of baseline (BL) and was maintained for 3 hours. Colonic blood flow was then restored, and the colon was reperfused for an additional 3 hours. One of 5 drug solutions was administered via the jugular vein 30 minutes prior to colonic reperfusion: group 1, 0.9% NaCl; group 2, dimethyl sulfoxide: 1 g/kg of body weight; group 3, allopurinol: 25 mg/kg; group 4, 21-aminost...
Kinetic studies and production rate of melatonin in pony mares. The aims of the present study were to determine basic kinetic parameters and the nycthemeral production rate of melatonin in the horse. Seven pony mares were used for the kinetic studies. Five other pony mares were used under long and short days for the production rate studies. Melatonin was administered by intravenous, oral, and intragastric routes at different dose levels. The plasma melatonin clearance was 1.02 +/- 0.31 l.kg-1.h-1, and the volume of distribution was 0.89 +/- 0.53 l/kg for the 0.4 microgram/kg melatonin dose. The systemic availability after oral and intragastric administrati...
Cardiovascular, respiratory and metabolic effects of interval training at VLA4. The purpose of this study was to determine if training with short intervals at the velocity producing a lactate level of 4 mmol/l (VLA4) is sufficient to induce adaptations and better exercise tolerance. Five Standardbred mares (4-8 years) were interval trained on a treadmill 3 days a week for 12 weeks and subsequently detrained for 4 weeks. Standardized exercise tests were performed before, during and after the training period and muscle biopsies were taken. Measurements were made of heart rate, oxygen consumption, stride frequency, blood volume and blood lactate. Plasma volume was reduced af...
Blood gas values during intermittent positive pressure ventilation and spontaneous ventilation in 160 anesthetized horses positioned in lateral or dorsal recumbency. One hundred sixty horses were anesthetized with xylazine, guaifenesin, thiamylal, and halothane for elective soft tissue and orthopedic procedures. Horses were randomly assigned to one of four groups. Group 1 (n = 40): Horses positioned in lateral (LRG1; n = 20) or dorsal (DRG1; n = 20) recumbency breathed spontaneously throughout anesthesia. Group 2 (n = 40): Intermittent positive pressure ventilation (IPPV) was instituted throughout anesthesia in horses positioned in lateral (LRG2; n = 20) or dorsal (DRG2; n = 20) recumbency. Group 3 (n = 40): Horses positioned in lateral (LRG3; n = 20) or d...
Plasma atrial natriuretic peptide in standardbred and Finnhorse trotters during and after exercise. To study the exercise-induced changes in atrial natriuretic peptide (ANP), a hormone with cardiovascular and renal effects, an incremental submaximal exercise test on a high-speed treadmill was carried out with Standardbred and Finnhorse trotters, the former bred for speed and the latter originally for heavy work. Standardbreds performed the 2 min exercise intervals at speeds of 6, 7, 8, 9 m s-1 and Finnhorses, according to their training status, at 5, 6, 7, 8 m s-1, 4, 5, 6, 7 m s-1 or 5, 6, 7 m s-1. Steady-state heart rate (HR) was reached within each 2 min interval. The increase in HR was l...
Lactate influx into red blood cells of athletic and nonathletic species. Transport of lactate across the erythrocyte membrane proceeds by three distinct pathways: 1) nonionic diffusion of lactic acid, 2) inorganic anion exchange (band 3), and 3) a monocarboxylate-specific (MC) carrier mechanism. This study determined the contributions of these three pathways in the red blood cells (RBCs) of "athletic" and "nonathletic" species. Blood samples were obtained from four male animals of each species: 1) Canis familiaris (dogs), 2) Capra hircus (goats), 3) Equus caballus (horses), and 4) Bos taurus (cattle). Contribution of each pathway to total lactate influx was determi...
Mechanisms of gastrointestinal ischemia-reperfusion injury and potential therapeutic interventions: a review and its implications in the horse. Restoration of blood flow after a period of intestinal ischemia is necessary to maintain cell function and viability; however, the reintroduction of oxygen can initiate a cascade of events that exacerbates tissue injury. Intestinal I-R injury is manifested as increased microvascular and mucosal permeability, and mucosal necrosis. Reperfusion injury begins with the accumulation of hypoxanthine from ATP metabolism and the conversion of XDH to XO during ischemia. Upon reperfusion, the XO catalyzes the conversion of hypoxanthine to superoxide radicals in the presence of oxygen. Superoxide radicals...
