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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.
Measurements of urethral pressure profiles in the male horse. Urinary tract pressure profiles were evaluated in 6 clinically normal geldings over 3 consecutive days. This was performed by introducing a 1.3 m-long cuffed catheter into the urinary tract, under xylazine sedation (0.8 mg/kg, iv). The method was reproducible. The mean (+/- sd) intra-vesicular pressure (IVP) and maximal urethral closure pressures (MUCP) were 10.3 (+/- 1.7) and 129.8 (+/- 19.6) cmH2O, respectively, and the ratio between MUCP and IVP was 13.2 (+/- 2.5). A gelding with urinary incontinence showed a significantly lower MUCP (73.4 cmH2O), and an MUCP to IVP ratio of 8.0. It was con...
Binding of epidermal growth factor and transforming growth factor-alpha in mammalian preimplantation embryos. Preimplantation embryos of the pig (Days 11 to 15), cow (Days 14 to 16), sheep (Day 14) and pony (Day 16) bind epidermal growth factor (EGF) specifically. Binding was not detected in embryos of the rabbit at Day 5 or 6 or the hamster at Day 3. Transforming growth factor-alpha displaced [(125)I] EGF in pig, cow and pony embryos almost as much as unlabeled EGF. The binding affinities of EGF ranged from 12 to 233 pM in pig and cow embryos. The range of species and binding features indicate that the EGF family may play a significant role in mammalian preimplantation development.
The equine placenta and equine chorionic gonadotrophin–an overview. Chorionic gonadotrophins seem to be unique for primate and equid species. Unlike primates, the equine conceptus does not implant in the maternal uterine endometrium until around day 37 of pregnancy. At this time specialized cells of the trophoblast, organized in the embryonic girdle, invade the endometrium and become established in the endometrial stroma, forming the so-called endometrial cups. This migration of girdle cells is accompanied by their morphological transformation into large decidual-like cells and by the appearance of a gonadotrophic hormone in the mare's blood. There is convinci...
The horse feto-placental unit. In the pregnant mare two different groups of oestrogens are produced by the placenta. The precursor of "classical" oestrogens (oestrone, oestradiol-17 beta and oestradiol-17 alpha) is dehydroepiandrosterone which originates from the fetal gonads. The ring B unsaturated oestrogens (equilin and equilenin and their derivatives) derive from farnesyl pyrophosphate by a pathway not involving cholesterol.
Age-related storage of iron in the liver of horses. The non-haem iron concentration was estimated in post-mortem liver samples from 51 horses (age range 1-25 years). Two were normal and 49 had been suffering from conditions that were not expected to have had long-term effects on iron metabolism. Muscle samples (splenius and biceps femoris) from 23 of these horses were also analysed. There was a highly significant age-related increase in the non-haem iron concentration in the liver (r = 0.635, p < 0.001), but not in the muscles, in which the iron concentration was much lower than in the liver.
Urinary concentration of corticoids in normal horses and horses with hyperadrenocorticism. The urinary corticoid:creatinine (c:c) ratio was determined in eight horses with hyperadrenocorticism (HAC). The mean (+/- SD) urinary c:c ratio of the eight horses with HAC (29 +/- 14 x 10(-6)) was significantly (P < 0.05) greater than the ratio in seven control horses (11 +/- 4.3 x 10(-6)). The urinary concentration of corticoids in control horses (201 +/- 60.4 nmol litre-1) was significantly (P 0.05) between both groups. As both false negative and false positive cases were found, it is concluded that a measurement of the urinary c:c ratio in the horse should not be used as the sole test...
Insemination results with slow-cooled stallion semen stored for approximately 40 hours. Semen from 3 stallions was extended using 2 methods (Kenney extender and a modified Kenney extender), slowly cooled, and stored for 41 +/- 6 (s.d.) h before insemination. An insemination dose (40 ml) contained 1.5-2 billion spermatozoa. In the experiment, 26 mares were inseminated in 30 cycles. The pregnancy rate per cycle obtained with sperm stored in the Kenney extender was 87% (n = 15). When the semen was extended with the modified extender, centrifuged and stored, the pregnancy rate was 60% (n = 15). Inseminations were done every other day until ovulation was detected. If a mare ovulated m...
[Ultrasonography of ovarian pathology in the mare: a review for the practitioner]. The aim of this review is to give the practitioner the ability to be familiar with the echographic exam of ovarian abnormalities. He should be able to recognize different stages of the development of these important structures and to estimate the effect that they can have on the normal cycle of the mare. Various specific criteria and details regarding the equine echography of ovarian abnormalities are reported and illustrated, using the last scientific data published on that particular topic.
[Ultrasonography of the formation and development of the corpus luteum in the mare: review for the practitioner]. Because of the anatomical position of the Corpus luteum within the ovary, rectal palpation is of little value for identification and evaluation. The aim of this review is to familiarize the practitioner with the echographic examination of the Cl. He should be able to recognize different stages of this important structure and to correlate ovulation and the existence of the Cl. Various specific criteria and details regarding equine echography are reported and illustrated, using the the most recently published scientific data.
Pregnancies following transfer of equine embryos cryopreserved by vitrification. The objective of this study was to investigate the in vitro and in vivo developmental abilities of equine embryos cryopreserved by vitrification. Twenty-eight embryos were recovered from Native pony and Thoroughbred mares at Days 5 to 7 by nonsurgical uterine flushing (detection of ovulation=Day 0). The vitrification solution contained 40% ethylene glycol, 18% Ficoll, and 0.3 M sucrose in PBS. The embryos were placed for 1 to 2 min in vitrification solution (Group 1) or following exposure to 20% ethylene glycol in PBS for 10 to 20 min (Groups 2 and 3). Single embryos were loaded in 0.25-ml str...
The role of sweat in maintaining the stimulation of effort homeostasis in horses. Sweat secretion was analyzed quantitatively and qualitatively in 20 horses after a 5 min. gallop at 450 m/min. The analysis revealed concentration of proteins 63.3 +/- 6.47 g/l, mainly albumins, a high level of sodium 254.43 +/- 62.84 mM/,l chloride 268.68 +/- 98.46 mM/l, potassium 98.95 +/- 49.62 mM/l and calcium 4.14 +/- 0.8 mM/l. A dependence was found between the protein concentration in serum and its quantity in sweat and between the level of potassium in sweat and its loss from the cells within a range 8.6 to 25.8 mM/l. The hypertonic horse sweat protects organism for excessive water los...
Fine structure of equine oocytes matured in vitro for 15 hours. Transmission electron microscopy (TEM) was used to evaluate the fine structure of equine oocytes cultured in vitro. Oocytes obtained by follicular aspiration were cultured for either zero or 15 hr. After treatment oocytes were processed either by light microscopy (nuclear evaluation) or TEM (cytoplasmic evaluation). Those oocytes cultured for 15 hr were incubated in modified TCM 199 with 15% (v/v) mare serum (day of ovulation) at 39 +/- 0.2 degree C. Evaluation using TEM revealed that cortical granules were present in all oocytes. However, zero-time oocytes contained few cortical granules, and...
Post-thaw motility and longevity of motility of imipramine-induced ejaculates of pony stallions. Imipramine-induced ex copula ejaculates (11) and fractionated in copula ejaculates were collected from each of 5 pony stallions for freezing in 5-ml straws (6), using a modified Kenney glucose skim-milk extender (2). Initial post-thaw total and progressive motilities and daily post-thaw total and progressive motilities, as well as the number of days to reach 0 progressively motile spermatozoa, were also similar for the 2 methods of collection. The percentage of morphologically normal spermatozoa both before freezing and after thawing were also similar for in copula and ex copula ejaculates. Co...
Proteolytic enzymes in equine joints with infectious arthritis. Significant amounts of collagenase and caseinase activity were detected in infected synovial fluid samples. Partial characterisation of the enzymes by gel filtration suggested that synovial fluid from cases of infectious arthritis may contain enzymes from both the synovial cells and neutrophils. This finding was also supported by analysis of sequential synovial fluid samples from 4 infected joints. In 3 joints the concentration of caseinase and in 1 joint collagenase paralleled the decline in total nucleated cell count. However, in 3 joints the concentration of collagenase remained high after ...
[The genital microflora in the stallion–microbiological study of presecretion samples from 1972 to 1991]. From 1972 to 1991, presecretion on an average of 183 stallions per year had been examined. Facultatively pathogenic germs were ascertained in 13.5% of the samples. However, the portion showed considerable annual fluctuation, as did the percentage of the different kinds of germs. In most of the cases, only minimal growth had been observed in culture. Except for the total percentage, these results are contradictory to those we found during the examination of cervical swabs of mares. In order to ascertain the importance of the respective results and to render possible a correct interpretation, th...
Equine fetal kinetics: entry and retention of fetal hind limbs in a uterine horn. Transrectal ultrasonic examinations were made in 31 pregnant pony mares once a week during Months 6 to 11. Each uterine horn was divided into 3 approximately equal segments (caudal, middle, cranial). The percentage of examinations with cranial fetal presentation increased (P<0.05) progressively from 58% at Month 6 to 99% at Month 9 and was followed in all mares by entry of the fetal hind limbs into one uterine horn. The mean number of uterinehorn segments with limb parts increased (P<0.05) between each set of consecutive months from Month 6 to Month 10. Initially (Months 7 and 8), retrac...
Respiratory mechanics of the horse during the first year of life. This study investigated the developmental changes in the mechanical properties of the respiratory system in growing horses. Pulmonary mechanics and lung volumes were serially measured in anesthetized foals during the first year of life. Quasi-static pressure-volume curves were generated, and functional residual capacity (FRC) was measured using a closed nitrogen equilibration technique. At birth, chest wall compliance normalized to body weight was substantially less than that reported in other less precocious newborn species, while lung compliance normalized to body weight was similar to value...
Metallothionein in platelets. The zinc content in platelets from rabbits, humans and horses was determined, and the levels of zinc were found to be significantly higher (3 micrograms/10(10) cells) than those in other peripheral blood cells. About 70% of the zinc in the supernatants of platelet lysates could be detected. From the results of gel filtration analysis, the zinc in platelet lysates was found to be bound with a low-molecular-weight protein (MW 6,000-8,000) detected as metallothionein (MT) on the basis of antigenic properties determined by enzyme-linked immunoassay and immunoblotting analysis using monoclonal anti...
Caffeine clearance in the horse. The pharmacokinetic properties of intravenously administered caffeine were studied in 10 horses using a commercially available automated enzyme immunoassay. The harmonic mean for the distribution half-life was 5.2 min (range 1.4-18.7). The harmonic mean for the elimination half-life was 10.18 h (range 6.82-20.92). The harmonic mean of the volume of distribution was 0.32 L/kg (range 0.22-0.53). There was no correlation between the dose of caffeine/kg body weight and the elimination half-life (Spearman's coefficient of rank correlation = 0.19).
The effects of exercise training on serum gastrin responses in the horse. Gastroendoscopic surveys have shown that horses in race training have a greater prevalence of gastric ulceration than sedentary horses. To determine if exercise affects gastric endocrine function the following experiment was performed. Four horses were fed total mixed ration of ground corn and chopped hay at 2% of their body weight, divided into 2 equal portions, daily. Horses were fasted overnight, and serum gastrin concentration was determined just before and 2 hours after feeding. The horses were then sprint trained on a high speed treadmill for 6 weeks. The response of serum gastrin to fee...
Secretagogue-induced [14C]aminopyrine uptake in isolated equine parietal cells. Equine oxyntic mucosal cells were obtained by sequential exposure to pronase and collagenase. Acid production by parietal cells was assessed by uptake of [14C]aminopyrine (AP), a weak base that accumulates in intracellular acidic spaces. Incubation for various times revealed a maximal AP uptake at 10 minutes for histamine and carbachol. Similar secretagogue responses were observed for parietal cells from the mucosal cell preparation or after enrichment by elutriation. Histamine and isobutyl-methylxanthine (IBMX) stimulated AP uptake with a dose-dependent response and maximal effective concentr...
Influence of intra-articular sodium hyaluronate and polysulphated glycosaminoglycans on the biochemical composition of equine articular surface repair tissue. The influence of repeated intra-articular injections of sodium hyaluronate and polysulphated glycosaminoglycan on the repair of full-thickness osteochondral defects was examined in the midcarpal joints of ponies. The study showed no significant difference between treated and control groups with regard to total collagen content, uronic acid content or the relative proportions of Type I and Type II collagen in the repair tissue, indicating that the drugs did not affect the biochemical composition of the repair tissue 11 weeks after defect induction.
Glucose transport and glycolytic enzyme activities in erythrocytes of two-year-old thoroughbreds undergoing training exercise. D-Glucose transport and cytosolic enzyme activities were measured in erythrocytes from 2-year-old thoroughbreds under continuous training exercise (race horses) and compared with those from untrained horses of various ages (sires, mares and untrained 2-year-old thoroughbreds). The activities of the glucose transport and glycolytic enzymes, hexokinase and pyruvate kinase, in the race horses' erythrocytes were elevated to 2-3.5 times above those of untrained horses. There were no significant differences in plasma glucose, triglyceride or IRI concentrations between the horses in training and untr...
Inhibitory nerve distribution and mediation of NANC relaxation by nitric oxide in horse airways. The distribution of inhibitory nerves and the mediator of the inhibitory nonadrenergic noncholinergic (iN-ANC) nervous system were investigated in smooth muscle preparations from seven regions of equine airways. In tissues incubated with atropine and precontracted with histamine, electrical field stimulation produced frequency-dependent relaxation, and the magnitude of the relaxation decreased from trachea to central bronchi and was absent in peripheral airways. The degree of relaxation in bronchi was not simply a function of bronchial size or generation. Propranolol inhibited part of the rela...
Preservation of ejaculated and epididymal stallion spermatozoa by cooling and freezing. The suitability of ejaculated and epididymal stallion spermatozoa for cooled storage (5 degrees C) and cryopreservation was examined in 5 ejaculates from each of 6 stallions and in spermatozoa recovered from the cauda epididymidis after castration of these stallions. The percentage of progressively motile spermatozoa, examined by subjective estimation (cooled samples) or by computerized analysis (frozen-thawed samples), was used as parameter. In ejaculated semen samples containing 5 and 25% seminal plasma in a skim milk glucose extender, the lower amount of seminal plasma supported spermatozoa...
Influence of air movement, facemask design and exercise on upper airway, transpulmonary, and transdiaphragmatic pressures in thoroughbred horses. The influences of facial airflow, exercise and wearing a facemask on gas exchange and upper airway (Pu), transpulmonary (PTP) and transdiaphragmatic (PTD) pressures were investigated in 6 horses performing an incremental exercise test on an inclined (10%) treadmill. The test consisted of a 2 min walk followed by two 2 min exercise bouts at intensities which produced 40% and 80% of maximal oxygen consumption. Horses performed the test 4 times, once for each of 4 protocols, which involved not wearing a facemask (A), wearing a mask with either no biased flow through it (B), with an expiratory bia...
Fibre type distribution, capillarization and enzymatic profile of locomotor and nonlocomotor muscles of horses and steers. Samples were taken at slaughter from heart and both locomotor and nonlocomotor muscles from animals of similar body weight but adapted to different levels of activity: three horses and three steers. All samples were analyzed biochemically to measure the activity of key metabolic enzymes. The skeletal muscles were analyzed histochemically for fibre type composition, fibre area and capillary supply. The general pattern of differences in fibre type composition and metabolic profile between muscle groups was similar in both horses and steers. The hearts of both species had high citrate synthase (C...
