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.
Johnson L, Varner DD, Thompson DL.To determine the age at which adult values for hormonal and testicular characteristics are established, testes and blood from 123 slaughtered horses, aged 1-5 years, were compared. Serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone (T) and intratesticular testosterone (ITT) were determined by radio-immunoassay. Specimens were obtained in the non-breeding (n = 46) or breeding (n = 43) season in Experiment 1 (Exp. 1) and in the breeding (n = 34) season in Experiment 2 (Exp. 2). Testicular parenchyma was fixed in glutaraldehyde and homogenized to...
Williams DO, Boatwright RB, Rugh KS, Garner HE, Griggs DM.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...
Fernandes I, Takehara HA, Mota I.Horse immunoglobulins were obtained from normal serum defatted with dextran sulfate and precipitated with ammonium sulfate. Eight mg of this preparation was submitted to affinity chromatography with protein A-Sepharose CL-4B. Low temperature (4 degrees C) and a starting buffer at pH 8.0 were conditions required for all IgG subclasses to bind to protein A, even those with low affinity. The IgGs bound to protein A were eluted with glycine buffer at pH 2.8. The yield was about 90%. It is suggested that isolated IgG, instead of whole Igs, be used in serum therapy, reducing the amount of Igs and di...
Hamon M, Clarke SW, Houghton E, Fowden AL, Silver M, Rossdale PD, Ousey JC, Heap RB.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...
Penhallow RC, Mason AB, Woodworth RC.1. Human, bovine and equine transferrins have been characterized with respect to mol. wt, and behavior on urea-polyacrylamide gels, and isoelectric focussing gels. 2. As shown by SDS-polyacrylamide gel electrophoresis human transferrin has one major polypeptide whereas both bovine and equine transferrins have two polypeptides. 3. The transferrins show multiple banded patterns on urea-polyacrylamide and isoelectric focussing gels, particularly when iron saturated. The various forms are not resolved by neuraminidase treatment.
Wilson DA, Baker GJ, Pijanowski GJ, Boero MJ, Badertscher RR.Suspensory ligaments (SL) from 32 Thoroughbreds and 32 Standardbreds were collected to evaluate the variation in muscle content with respect to age, breed, sex, limb, and use. Six transverse sections, each 3 to 5 mm thick, were obtained from each SL. Four sections were taken from the body of the SL and 1 from the midportion of each branch. Sections were stained with van Gieson picric acid-fuchsin solution, then photographed, and black-and-white slides were made from the processed negatives. The transverse-sectional area of the SL and the contained muscle were determined by use of a computer wi...
Ferlazzo AM, Vinci R, Panzera M, Ferlazzo A, Calatroni A.1. The measured values of acid glycosaminoglycan (GAG) concentration in plasma or in serum show significant differences between trained and untrained horses and among sedentary horses and other animal species (cattle, rabbit, sheep). 2. Diurnal variations in serum GAG levels are reported (cattle), and changes in plasma GAG concentrations after road transport (horses) and in late pregnancy (mares, cows), while sex, age and breed do not affect them.
Jiang B, Rugh KS, Hatfield DG, Jiang D, Hahn AW.We report on a nonlinear algorithm which identifies R-wave peaks on the surface electrocardiogram, consistent reference points on the left ventricular pressure waveform and the initiation of the QRS complex on the epicardial electrogram. The algorithm has been used to evaluate data from horses, ponies, dogs and humans at rest and during exercise. It permits rapid, accurate evaluation of data on a beat-by-beat basis even with noisy signals and varying waveform configurations. The algorithm facilitates the acquisition of detailed information previously difficult or impossible to obtain by more c...
Clark ES, Gantley B, Moore JN.The effects of intravenous (iv) infusion of endotoxin for 60 mins at a cumulative dosage of 0.03 micrograms/kg bodyweight on systemic arterial, right atrial and pulmonary arterial pressures, heart rate, cardiac output, and derived pulmonary vascular resistance and total peripheral vascular resistance were compared to the effects of iv infusion of saline solution in four healthy horses. Heart rate was increased significantly after endotoxin infusion, although diastolic arterial pressure, systolic arterial pressure, electronically averaged arterial pressure, cardiac output, total peripheral resi...
Affleck KJ, Conboy HS, Fitzgerald BP.Eleven anoestrous mares were assigned randomly to Group A (intact, n = 6) or Group B (ovariectomized in January, n = 5). Jugular blood samples were collected during February to April. Ovarian activity was assessed by ultrasound and ovulation was confirmed by progesterone analysis. Intact mares ovulated between 2 and 28 April. Mean diameter of the largest follicle was less than 20 mm on 17 or 18 March (Period 3), but increased to 29 mm by 31 March or 1 April (Period 4). During Periods 1 and 2 (14 or 15 February and 3 or 4 March) mean luteinizing hormone (LH) concentrations were similar in both ...
King JN, Gerring EL.Post operative ileus (POI) is a common and serious complication of colic surgery in the horse. There is a high correlation between the incidence of POI and the presence of ischaemic bowel, suggesting a role for endotoxin. 0.1 micrograms/kg endotoxin was administered intravenously to six ponies with chronically implanted gastrointestinal electromechanical recording devices. It produced profound disruption of normal fasting bowel motility patterns, with an inhibition of gastric contraction amplitude and rate, left dorsal colon contraction product and small colon spike rate. In the small intestin...
Skelton KV, Dowsett KF, McMeniman NP.This study investigated the effects of zero, low (0.55), medium (1.1) and high (2.2 mg/kg LW) boldenone undecylenate on the reproductive physiology of sixteen fillies from the ages of 7 to 11 months until 2 years. Ovarian activity measured by cross-sectional area, total number of ovulations, total number of follicles and the number of large follicles (greater than 30 mm in diameter) was significantly reduced by steroid treatments. Of fillies that ovulated during the first breeding season, the age of first ovulation and the second breeding season was significantly delayed in the high dose group...
Alexander SL, Irvine CH, Ellis MJ, Donald RA.We have used the technique which we have developed for collecting pituitary venous blood from conscious, undisturbed horses to study the effect of acute vigorous exercise on the secretion of CRF, arginine vasopressin (AVP) and ACTH. Pituitary venous (pit) blood was collected every 1-5 min from nine trained racehorses at rest in the stable. The horses then trotted quietly for 10 min, after which they galloped as fast as possible for 4-6 min, before returning to the stable where sampling continued. In Exp 1 (n = 5) no blood samples were taken during exercise, whereas in Exp 2 (n = 4), pit blood ...
Gill J.1. The use of an electronic recorder for the horse motor activity was described. 2. Examples of different types of motor activities are given in Figs 1-8. 3. The ultradian pattern of activity in all records was stressed. 4. The possibility of receiving of more physiological informations by this type of apparatus is discussed.
Koskinen E, Katila T.The luteal activity in mares was studied in the Equine Research Station (ERS) and in trotting stables (TS) in South-Finland. The mares were Standardbreeds in the TS and mainly Finnhorses in the ERS. Between January and June blood was collected once a week for serum progesterone determinations. The mares in the ERS were distributed in 1 of 3 groups: three-years old not yet in training (N = 38), brood mares (N = 21) and mares in training (N = 47). A 4th group was the mares in training in the trotting stables (N = 73). Every 5th mare in the ERS and every 4th mare in the trotting stables were cycl...
Shand N, Alexander SL, Irvine CH.For aqueous extracts of pituitary glands of oestrous mares, luteinizing hormone (LH) profiles were found to be similar to each other and to earlier work after chromatofocussing (CF) and isoelectricfocussing (IEF). After CF, both LH and follicle-stimulating hormone (FSH) in pituitary extracts focussed in multiple peaks in the acidic range, with 86% of LH and 80% of FSH found between pH 4 and 6. By contrast, in pituitary venous plasma, only 18% of the LH focussed in this range, whereas a significantly greater proportion (P less than 0.01) eluted above pH 7 than occurred in pituitary extracts (37...
Hässig M, Casal M, Von Beust B, Nussbaumer M, Rüsch P.In human cancer treatment, CEA (carcino embryonic antigen) testing is a routine procedure, even though the test is of low sensitivity (40%) and low specificity (70%). Since tests with polyclonal antibodies render no reproducible results with animal sera, the applicability of a recently available monoclonal CEA test designed for human sera was evaluated. We were able to show that the latter test was of supplemental diagnostic value when testing animal sera. The upper normal limit for dogs is 1.65 ng/ml, for cats 2.81 ng/ml, for cows 2.85 ng/ml, for sheep 2.85 ng/ml and for horses 1.61 ng/ml.
Seither RL, Brown OR, Babu BV.Rat, cow and foal lung extracts contained an inhibitor for the liver NAD biosynthetic-pathway enzyme, nicotinatemononucleotide pyrophosphorylase (carboxylating) [EC 2.4.2.19]. The inhibitor was not dialyzable, was labile at 100 degrees C, was retained by a 30,000 dalton pore size Amicon membrane and, when partially purified by precipitation at 40-100% ammonium sulfate, inhibited the enzyme stoichiometrically. Lung reportedly does not contain nicotinate-mononucleotide pyrophosphorylase or make NAD de novo. However, the inhibitor would mask detection of the enzyme in lung extracts. We detected a...
May SA, Hooke RE, Lees P.The concentration of Percoll required for isolating equine peripheral blood mononuclear cells has been reinvestigated. A poor cell yield was obtained at the 60 per cent concentration already reported. It is recommended that workers specifically interested in high yields of mononuclear cells, for investigation of lymphocyte and monocyte functions, use a concentration of 65 per cent Percoll. However, workers wishing to isolate pure populations of equine neutrophils might consider a concentration of 70 per cent in the upper layer of Percoll used to retain the mononuclear cells.
Orsini JA, Dreyfuss DJ, Vecchione J, Spencer PA, Uhlman R.The effects of a potent new histamine-2 (H2) receptor antagonist, BMY-25368, were studied on gastric acid secretion in 5 foals from which food was withheld. Doses of 0.02, 0.11, 0.22, and 1.10 mg/kg of body weight were administered IM in a randomly assigned treatment sequence. Following BMY-25368 administration, hydrogen ion concentration was decreased and mean pH was higher than baseline values in a dose-response pattern. At the 0.22 and 1.10 mg/kg doses, the high pH was sustained for greater than 4 hours. The BMY-25368 thus may be useful for treating gastric ulcer disease in horses.
Irvine CH, Alexander SL.In an experiment conducted late in the physiological breeding season, 5 stallions were fitted with indwelling pituitary venous cannulae that permitted unobtrusive collection of blood coming from the pituitary and the hypothalamo-hypophyseal portal vessels. The next day, blood samples were collected at 5 min intervals for several hours while the stallions were resting. Pulses of gonadotrophin-releasing hormone (GnRH), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) occurred approximately once per hour. After this, an oestrous mare was brought into contact with each stallion for ...
Cothran EG, Henney PJ, King JA.The inheritance of the equine Tf F3 allele was examined in 39 parent-offspring combinations. For 26 of the cases the allele inherited by the offspring from the heterozygous parent could be determined. The proportion of individuals that inherited the F3 variant compared to the alternative allele was exactly 1:1. In five cases the parental phenotype was identical to that of the offspring. For the remaining eight cases the parent was homozygous for the F3 allele and all offspring had the F3 allele. The results were consistent with Mendelian inheritance.
Brewer BD, Clement SF, Lotz WS, Gronwall R.Urine (U) and serum (S) were obtained every 2 hours during a 12- or 24-hour period from eight healthy 96-hour-old pony or horse foals. Dams' milk samples were obtained concurrently. Urine volume was measured during this 12- or 24-hour period. The mean amount of urine produced was 148 +/- 20 ml/kg/day. Baseline urinalyses were evaluated on all foals at two days of age, before any manipulation. Urine generally was dilute (less than 1.008) but the specific gravity was as high as 1.027 in one normal foal. Continuous (12 or 24 hour) urinary catheterization resulted in bacteriuria but not white bloo...
Holtan DW, Houghton E, Silver M, Fowden AL, Ousey J, Rossdale PD.This study used gas chromatography/mass spectrometry (GC/MS) to identify and measure plasma progestagens. The method included deuterated internal standards, e.g. [17,21,21,21-2H]-5 alpha-pregnane-3,20-dione, solid-phase extraction, derivatization (methoxime/t-butyldimethylsilyl) and GC/MS. Full-scan screening identified 3 5-pregnenes, 2 4-pregnenes and 7 5 alpha-pregnanes (no 5 beta-pregnanes). The selected ion mode was used for routine quantitation from calibration curves; response was linear (r greater than 0.98) from 2 to 2000 ng equivalents/ml (0.5 ng/ml method sensitivity) and intra- and ...
Bowling AT, Williams MJ.Two additional specificities (Dq and Dr) were assigned to the D system of horse red cell alloantigens following discussion of the 1989 ISAG Horse Comparison Test (HCT) results. Family and population data support 25 phenogroups defined by the enhanced battery of 17 D system factors.
Freitas TV, Fortes-Dias CL, Diniz CR, Velarde DT, Freitas CF.1. A comparative study was carried out on horses immunized with Crotalus durissus terrificus venom using four different inoculation procedures, which included the use of Freund's adjuvant, A1(OH)3 and liposomes as adjuvants. The antibody titer was assessed by enzyme linked immunosorbent assay (ELISA) and the neutralizing potency by the neutralizing median effective dose (ED50). 2. The inoculation schedule used in horses to obtain antivenom serum consisted of sc injections of a 7.5 mg venom starting dose in 5.0 ml sterile saline emulsified with an equal volume of Freund's complete adjuvant. One...
Thompson DL, Reville SI, Walker MP, Derrick DJ, Papkoff H.To study the possible role of ovarian androgens in regulation of follicle stimulating hormone (FSH) secretion in the cycling mare, five mature, intact mares were treated with testosterone (20 micrograms/kg of body weight) daily during estrus; five control mares received safflower oil on the same schedule. Mares were teased for estrus and samples of jugular blood were drawn daily through one full estrous cycle. Concentrations of FSH in plasma were measured by a newly developed radioimmunoassay based on anti-ovine FSH serum and radioiodinated equine FSH. Testosterone treatment during estrus had ...
Baeyens WR, Van der Weken G, Haustraete J, Aboul-Enein HY, Corveleyn S, Remon JP, García-Campaña AM, Deprez P.The group of LiChrospher ADS (alkyl-diol silica) sorbents that make part of a unique family of restricted-access materials, have been developed as special packings for precolumns used in the LC-integrated sample processing of biofluids. The advantage of these sorbents lies in the direct injection of untreated biological fluids, that is without sample clean-up, the elimination of the protein matrix with a quantitative recovery together with an on-column enrichment. The present method is based on previous work applying UV detection at 260 nm for ketoprofen determinations. Plasma samples introduc...
Imai S, Ozeki K, Fujita J.The surface structure of the ciliary zone in 13 species of ciliates found in the large intestine of the horse was observed by scanning electron microscopy. In Holophryoides ovalis many fine depressions considered to be a result of phagocytosis or pinocytosis in the naked cytostome were noticed. In Blepharocorys spp. a distinct section was present between the portion with cilia and that without cilia. It was not present, however, in some species of the family Buetschliidae, such as Bundleia postciliata and Didesmis spp. The species of Entodiniomorphida had a lip around the ciliary zone with cil...
Munsterman AS, Gillen AM, Coleridge MOD, Hanson RR.To evaluate the effect of changes in intra-abdominal pressure (IAP) on medial saphenous venous pressure (MSVP) and hemodynamics in normal horses. Methods: Experimental, in-vivo study. Methods: University Teaching Hospital. Methods: Convenience sample of 7 mixed breed horses; 5 geldings, and 2 mares. Methods: Pneumoperitoneum was induced in horses under standing sedation with carbon dioxide gas using a laparoscopic insufflator for a total of 60 minutes to simulate clinical elevation in IAP. Pressure was increased stepwise to 20 mm Hg over 30 minutes, and maintained at that pressure for 30 minu...
Mills JS, Kinsley MA, Peters DF, Weber PSD, Shearer TR, Pease AP.The purpose of this study was to determine whether there was a correlation between circulating and intra-synovial Dkk-1 and radiographic signs of equine osteoarthritis. Methods: Circulating and intra-synovial Dkk-1 levels were measured in clinical cases using a commercially available human Dkk-1 ELISA. Radiographs were performed of the joints from which fluid was collected and these were assessed and scored by a boarded radiologist for joint narrowing, subchondral bone sclerosis, subchondral bone lysis, and periarticular modelling. Comparisons were made between radiographic scores and the conc...
Carmalt JL, Allen AL.To evaluate the effect of rostrocaudal mobility (RCM) of the mandible during extension and flexion of the atlanto-occipital joint on weight gain, feed digestibility, and fecal particle size in horses. Methods: Randomized controlled trial. Methods: 34 pregnant mares housed in 1 barn. Methods: Horses were randomized into a treatment (n = 17) or control (17) group. All horses were sedated, and the distance between the rostral portions of the upper and lower incisor arcades was determined during extension and flexion of the atlanto-occipital joint; mandibular RCM was calculated as the difference b...
Arthur GH.The effect of intrauterine saline on reproductive function was studied by infusion of mares in anoestrus, dioestrus, oestrus and prolonged dioestrus. Anoestrous mares were unaffected except near the beginning and end of the breeding season when anovulatory heats were induced. Dioestrous mares infused between Days 5 and 9 returned to heat an average of 3-8 days earlier than expected, and infusions during dioestrus were followed by ovulatory heats of normal fertility. Three mares in prolonged dioestrus showed ovulatory heats within 3 to 9 days of infusion. Infusions during oestrus had no appreci...
Nieto JE, Morales B, Yamout SZ, Stanley SD, Harmon FA, Snyder JR.To determine the response to neostigmine of the contractile activity of the jejunum and pelvic flexure and the effects of a continuous rate infusion (CRI) of neostigmine in horses. Methods: 7 adult horses and tissue from 12 adult horses. Methods: A CRI of neostigmine (0.008 mg/kg/h) or placebo was administered to 6 horses in a crossover study design. Gastric emptying was evaluated by the acetaminophen test. The frequency of defecation and urination and the consistency and weight of feces were recorded throughout the experiment. The effect of neostigmine on smooth muscle contractile activity wa...
Engle CE, Foley CW, Witherspoon DM, Scarth RD, Goetsch DD.Three experiments were conducted on the metabolism of stallion sperm. In experiment 1, whole and washed sperm were incubated under aerobic and anaerobic enviroments and analyzed before and after controlled incubation for motility, pH, lactic acid, glucose, fructose, and O2 comsumption. In experiment 2, whole and washed sperm were incubated aerobically and anaerobically with and without uterine tubal fluids. Experiment 3 was the same as experiment 2, except added substrates of glucose and lactic acid were studied. The same examinations were made in experiments 2 and 3 as for experiment 1. Motil...
Ruiz Silva BE, Burtnick LD.Gelsolin can be purified from horse blood plasma by treating the plasma sequentially with an anion-exchange medium in the presence and then the absence of free Ca2+. The purified gelsolin migrates as a 90-kilodalton protein on electrophoresis in polyacrylamide gels in the presence of sodium dodecyl sulfate. It has an absorption coefficient of 1.4 mL/(mg.cm) and is similar in amino acid composition to other plasma gelsolins. Horse plasma gelsolin has an intrinsic sedimentation coefficient of 4.8S and a Stokes' radius of 3.8 nm. Hydrodynamic calculations suggest it to be a rather globular protei...
Burrows GE, MacAllister CG, Ewing P, Stair E, Tripp PW.The effects of time and method of administration of rifampin with respect to feeding were evaluated in five mature horses. There was a significant (P less than or equal to 0.05) delay in time of maximum serum concentration and an apparent but not significant decrease in oral absorption when rifampin was given as a top dressing on grain as compared with administration in corn syrup 2 h before or 2 h after feeding. Although there were no differences between administration before or after feeding, administration 2 h prior to feeding was selected as the method of choice for future experiments. The...
Menzies-Gow NJ, Sepulveda MF, Bailey SR, Cunningham FM, Elliott J.To evaluate the roles of 5-hydroxytryptamine (5-HT), thromboxane A2 (TxA2), and platelet-activating factor (PAF) in endotoxin-induced digital hypoperfusion in horses. Methods: 6 healthy adult Thoroughbreds. Methods: Horses were treated with IV administration of saline (0.9% NaCl) solution (control treatment) or the 5-HT 1B/D selective antagonist, GR55562 (0.3 mg/kg), prior to tryptamine infusion (1.6 microg/kg/min for 30 minutes) to establish an effective GR55562 dose. In a crossover study, horses were treated with IV administration of saline solution (control treatment), aspirin (4 mg/kg, 2 h...
Schumacher J, Chambers M, Hanselka DV, Morton LD.Eighteen stored split thickness meshed skin grafts were applied to surgically created lesions on the metacarpal and metatarsal regions of six horses. Donor skin was harvested from the sternal region, meshed and stored at 4 degrees C in a cell culture medium containing 10% serum. Stored grafts were applied to the wounds at 1, 2, and 3 week intervals. Acceptance of the grafts stored for 1 week was generally poor (1 of 6 grafts), whereas that of the 2 and 3 week old grafts was generally excellent (10 of 12 grafts). Poor acceptance of the 1 week old grafts was attributed to streptococcal infection...
Takahashi Y, Takahashi T, Mukai K, Ebisuda Y, Ohmura H.Given that Thoroughbred horses' canter is an asymmetric gait, not only speed but also leading or trailing limbs could affect muscle activities. However, the muscle activity during a canter remains poorly understood. Hence, we aimed to investigate speed and lead-side (leading or trailing) effects on surface electromyography (sEMG) during a canter. The sEMG data were recorded from left Musculus brachiocephalicus (Br), M. infraspinatus (Inf), long head of M. triceps brachii (TB), M. gluteus medius (GM), M. semitendinosus (ST), and M. flexor digitorum longus of seven Thoroughbreds with hoof-strain...
Madison JB, Gronwall RR.Three sets of paired circular and square full-thickness skin wounds were made on the dorsum of the metacarpus (n = 48) of 8 horses. Each wound was 6.25 cm2 in area. The wounds were treated topically with an ointment, nonadherent dressing, and bandaged with a snug elastic wrap. Wounds were photographed every other day until healing was complete. Wound areas were measured and exponential and linear wound healing models were applied to the wound healing data generated. Wound healing variables measured for each wound were: number of days to healing, maximal size attained, rate of wound contraction...
Nauwelaerts S, Clayton HM.Data describing segmental masses and moments of inertia (MOI) of limb segments are required for inverse dynamic calculations. In horses, these values are usually calculated using regression equations that have been developed from a limited number of horses representing a small number of breeds. The objective of the present study was to evaluate the performance of a scaling method and a pictorial method for estimating of the values of segmental masses, lengths, and MOI in the equine limb segments by comparing their output with the standard technique involving direct measurements. Limbs of 30 ho...
Watson ED, Stokes CR, Bourne FJ.Prostaglandins (PGs) F and E2 were measured in lavage fluid from the uterus of ovariectomised mares after experimental induction of uterine inflammation. Treatment with progesterone alone, or progesterone followed by oestradiol, significantly increased the concentrations of these PGs in the lavage compared with mares treated with oestradiol or control mares. Ovarian steroids, therefore, influenced uterine PG synthesis in response to an inflammatory stimulus. To determine whether the uterine lavage procedure might contribute to the concentrations of prostaglandins in the lavage, the procedure w...
Daels PF, Besognet B, Hansen B, Mohammed H, Odensvik K, Kindahl H.To determine the role of progesterone in the regulation of endogenous prostaglandin F2 alpha (PGF2 alpha) secretion during cloprostenol-induced abortion and to investigate use of progestins to prevent prostaglandin-associated abortion. Methods: 16 pregnant mares. Methods: To induce abortion, cloprostenol (250 micrograms/d) was administered daily until fetal expulsion or for up to 5 days. In experiment 1, 8 mares, 98 to 153 days' pregnant, received progesterone (300 mg/d) at 24-hour intervals for 5 days, starting 18 hours after the first cloprostenol administration. In experiment 2, 8 mares, 93...
Earley ET, Reiswig JD.Odontoplasty (floating and occlusal equilibration) is the most commonly performed procedure in equine dentistry. From an anatomic perspective, an irregular occlusal surface, prominent cingula, transverse ridges, and enamel points all contribute to the function, form, and longevity of the equine cheek tooth. With limited reserve crown available and an average functional life range between 18 and 25 years, removal of tooth structure should be conservative. The authors consider a quality oral examination to be the most important dental procedure performed in the horse. Individual tooth evaluatio...
Allen ML, Baker GJ, Freeman DE, Holmes KR, Marretta SM, Scoggins RD, Constable P.To measure the amount of heat generated during 3 methods of equine dental reduction with power instruments. Methods: In vitro study. Methods: 30 premolar and molar teeth removed from mandibles of 8 equine heads collected at an abbatoir. Methods: 38-gauge copper-constantan thermocouples were inserted into the lingual side of each tooth 15 mm (proximal) and 25 mm (distal) from the occlusal surface, at a depth of 5 mm, which placed the tip close to the pulp chamber. Group-NC1 (n = 10) teeth were ground for 1 minute without coolant, group-NC2 (10) teeth were ground for 2 minutes without coolant, a...
Kirkpatrick JF, Liu IM, Turner JW, Bernoco M.Twenty-six free-roaming feral mares were immunized against porcine zonae pellucidae (PZP) between February and May, 1988. Eight sexually mature mares received 2 inoculations 2 weeks apart, and 18 mares received 3 inoculations at intervals of 2 and 4 weeks. Analysis of urinary oestrone conjugates (E1C) and non-specific progesterone metabolites (iPdG) in samples collected in October, 1988, revealed that none of the 18 mares that received 3 and only 1 of the 6 mares that received two inoculations were pregnant, whereas 3 of 6 sham-injected control mares and 5 of 11 untreated mares were pregnant. ...
Ohta M, Kurimoto S, Tokushige H, Kuroda T, Ishikawa Y.To determine hemodynamic effects of hydroxyethyl starch (HES) infusion during anesthesia in horses, incremental doses of 6% HES were administered to 6 healthy Thoroughbred horses. Anesthesia was induced with xylazine, guaifenesin and thiopental and maintained with sevoflurane at 2.8% of end-tidal concentration in all horses. The horses were positioned in right lateral recumbency and administered 3 intravenous dose of 6% HES (5 ml/kg) over 15 min with 15-min intervals in addition to constant infusion of lactated Ringer's solution at 10 ml/kg/hr. Hemodynamic parameters were measured before and e...
Hubbell JA, Muir WW.The rate of rise of arterial partial pressure of carbon dioxide (PaCO2) was determined in 49 apneic halothane-anesthetized horses following controlled ventilation. Drugs given for induction of anesthesia did not affect the rapid rate of rise of PaCO2 during the first minute after controlled ventilation, the PaCO2 at 1 minute after controlled ventilation, or the PaCO2 at which spontaneous ventilation began. Horses given xylazine-ketamine for induction of anesthesia had a significantly (P less than 0.05) faster rate of rise of PaCO2 after 1 minute following controlled ventilation than did horses...
Martínez-Boví R, Zagrajczuk A, Donadeu FX, Skarzynski DJ, Piotrowska-Tomala K, Cuervo-Arango J.Haemorrhagic anovulatory follicles (HAFs) are the most common pathological anovulatory condition in the mare. To enhance understanding of the physiopathology of HAFs, the aim of the present study was to determine the effects of an induced-follicular wave on LH concentrations and follicular fluid factors relevant to the ovulatory process. Mares were allocated to treatment or control groups (n = 7/group) in a crossed over design during 14 oestrous cycles with a period of one cycle occurring when there were no treatments between the times when treatments were administered. In the treatment gr...
Grabowska A, Kozdrowski R.Progesterone plays a crucial role in the maintenance of pregnancy from conception to about 100-120 days of gestation when placenta becomes the main source of gestagens. The aim of the study was to test progesterone concentration 14 days after ovulation in pregnant mares and relate it to peak estral endometrial edema and the presence of intrauterine fluid (IUF) after artificial insemination (AI), the number of treatments against IUF, and the time from AI to the day when the uterus was found free of fluid. Results: Mares were divided into two groups: group A (n = 13; age 10.8 ± 4.5 y...
Pelletier N, Leith DE.Horses have high mean pulmonary artery pressure (Ppa) both at rest and during exercise (approximately 30 and > or = 80 mmHg, respectively). The mechanisms are unknown. To see if hypoxic pulmonary vasoconstriction (HPV) plays a role, we compared pulmonary artery pressure-flow (Ppa-Q) curves when inspired O2 fraction (FIO2) was 0.16, 0.21, and 0.30, in 5 normal Thoroughbred horses standing quietly and while galloping at 10 and 14 m/sec on a level treadmill. We calculated O2 consumption (VO2) from measurements of respired gas composition and flow, and calculated Q from VO2 and measurements of ...
Bowker RM, Rockershouser SJ, Linder K, Vex KB, Sonea IM, Caron JP.The innervation of the navicular bone (os sesamoideum distale) and its suspensory ligaments (ligamenta sesamoidea collateralia) (CSL) or proximal suspensory ligament and the ligamentum sesamoideum distale impar or the distal sesamoidean impar ligament (DS-impar ligament) was examined using combined anatomical techniques of silver impregnation and immunocytochemistry. Silver impregnation studies revealed an abundance of nerve fibres present in both the CSL and DS-impar ligament with the latter having relatively more nerve fibres. These silver-impregnated nerves coursed parallel to and were asso...
De Silva M, Tagliavia C, Galiazzo G, Gifuni G, Caiazza M, Chiocchetti R, Grandis A.The morphometric studies of the atrioventricular valves are still limited in the horse. Objective: To investigate the anatomy of the atrioventricular valves in the horse, focusing on the morphometric features of the valvular leaflets and the tendinous cords. We hypothesised that accessory leaflets occur commonly and exist as independent structures in the atrioventricular valves of the horse. Methods: Descriptive anatomical study. Methods: Twenty normal hearts from slaughtered half-bred horses were used. The cardiac weight and circumference were recorded. The atrioventricular valves were expose...
Kitzman JV, Wilson RC, Booth NH, Hendricks HL, Bush PB.The pharmacokinetics of 4-aminopyridine (4-AP), a drug capable of antagonizing nondepolarizing neuromuscular blocking drugs, as well as several classes of injectable sedative and anesthetic agents, were studied in 6 intact, awake horses. Plasma samples were assayed for 4-AP over a frequent sampling schedule for 8 hours after IV administration. The plasma 4-AP vs time data best fit a 2-compartment pharmacokinetic model. Distribution half-life was 7.4 minutes, elimination half-life was 259 minutes, volume of the central compartment was 0.89 L/kg, volume of distribution (area) was 1.98 L/kg, volu...
Hyland JH, Wright PJ, Clarke IJ, Carson RS, Langsford DA, Jeffcott LB.In Exp. 1, 30 Standardbred mares in deep seasonal anoestrus were divided into 3 equal groups and treated with 0, 50 (G50) or 100 (G100) ng GnRH kg-1h-1 for 28 days via osmotic minipumps. Ovulation occurred in 0/10, 3/10 and 7/10 mares respectively (P less than 0.05). Plasma GnRH profiles (Days -6, 0, 2, 6, 12, 20, 28 and 34 relative to pump insertion) were dose-dependent (P less than 0.01) and peaked on Day 12 of infusion. Mean daily plasma LH concentrations were biphasic in treated mares that ovulated, with LH peaks occurring around Day 6 and Days 16-20. By contrast, in treated mares that did...
