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.
Goulden BE, Anderson LJ, Davies AS, Barnes GR.A horse with rostral displacement of the palatopharyngeal arch was found to have a bilaterally symmetrical deformity of the laryngeal area. Both left and right cricopharyngeal muscles were absent. The shape of the thyroid cartilage was grossly abnormal and vestiges of the cricothyroid muscles were attached only to the cricoid cartilage. It was suggested that such an anomaly could have resulted from aberrant development of the fourth branchial arch.
Targowski SP.The present study describes a two step technique for the separation of mononuclear leukocytes or mononuclear and polymorphonuclear leukocytes from whole equine blood. First, the leukocyte rich plasma was obtained by sedimentation of erythrocytes in the undiluted blood. Subsequently, separation of the different populations of white blood cells was performed by centrifugation with different gradients overlaid with the leukocyte rich plasma. The optimal separation of the mononuclear cells was obtained by the centrifugation of the leukocyte rich plasma overlaying the gradient containing 24 parts o...
Johnson PE, Maister SG, Knowles JR.Phosphoglycerate kinase has been isolated in crystalline form from horse muscle. A convenient isolation procedure is described that yields homogeneous enzyme of specific activity 700 units/mg (30 degrees C). The enzyme is monomeric, and has a molecular weight 47 000. Of the eight cysteine residues in the protein, two react rapidly with Nbs21 with the concomitant loss of the catalytic activity. Since the isolation of phosphoglycerate kinase from yeast (Bücher, 1955) there have been several reports of purification methods yielding enzyme approaching molecular homogeneity, from rabbit muscle (Be...
Poskus E, Zakin MM, Fernámdez HN, Paladini AC.Peptide fragments, obtained from equine growth hormone by cyanogen bromide cleavage and further chemical treatment, were isolated and identified. Their immunological reactivities were tested by hemagglutination and complement fixation methods using rabbit antisera against native hormone. Antigenic determinants were detected in the fragments comprising amino acid sequences 5-72 and 73-123, this last one being predominant. Fragment 124-178 had very low reactivity. Nitration of peptide 73-123 did not modify its immunological properties,but oxidation diminished them. Comparison of the antigenicity...
Muir WW, Skarda RT, Milne DW.An evaluation and comparison of thermodilution technique with dye dilution technique was made in the computation of cardiac output in 39 conscious adult horses (av body wt, 450 kg). Estimation of cardiac output by thermodilution was found to compare favorably with values obtained from dye dilution when a volume of 30 to 40 ml at a temperature of 0 C was used. Difficulties in obtaining accurate thermodilution curves in the horse seem predominantly associated with errors in mixing and observation.
Sidhu GS, Brown MA, Johnson AR.Factors contributing to the initiation of lipid oxidation in cow's and mare's milk containing high levels of polyunsaturated fatty acids were studied. Addition of H2O2 just after milking, in slight excess of the stoichiometric amounts required to destroy ascorbic acid, delayed the development of oxidized flavours in cow's milk high in linoleic acid. Hydrogen peroxide treatment followed by the addition of alpha-or gamma-tocopherols prevented lipid oxidation in cow's milk even when 0.1 mg Cu/l milk was added. When used separately in the presence of Cu these treatments were ineffective as was but...
Gopinath G, Ford EJ.The hepatotoxic effect of oral halothane in the horse is increased by pretreatment with phenobarbitone or DDT but not by chlorpromazine. Phenobarbitone and DDT increase the activity of hepatic amidopyrine N-demethylase but chlorpromazine does not. Carbon disulphide protects the liver of the horse against halothane.
Brown MP, MacCallum FJ.Observations were made which may be related to growth plate disorders. They included irregularity and thickening of the growth plate bridging of the plate by bony spicules, distortion of the plate adjacent to foci of fusion, and metaphyseal lipping. These observations are very similar to those found in "epiphysitis." The question had to be asked, where these normal foals or did they have sub-clinical "epiphysitis"?
Ronda GJ, Gaastra W, Beintema JJ.The kinetic parameters Km, k+2 and k+2/Km of the pancreatic ribonucleases (EC 3.1.4.22) from cow, giraffe, horse, rat and lesser rorqual have been determined, using 2',3'-cyclic cytidine monophosphate and 2',3'-cuclic uridine monophosphate as substrates. No large differences were found between the activities of the five enzymes. The relative differences between the activities of the five enzymes are mainly due to differences in the rates of hydrolysis and not to differences in the affinities for the substrates.
Nett TM, Pickett BW, Seidel GE, Voss JL.Jugular venous blood was collected from 16 mares at daily intervals throughout the estrous cycle. Twelve of these mares were bred to fertile stallions. Of the twelve, four were palpated daily throughout the estrous cycle, four were palpated daily during estrus and four were not palpated. The remaining four mares were not palpated or bred and blood samples were collected at 6-h intervals during estrus. Serum was harvested from all blood samples by centrifugation. The serum samples were analyzed for luteinizing hormone (LH) and/or progesterone by radioimmunoassay. Levels of LH in serum increased...
El-Ghannam F, El-Sawaf S.A study of the estrus cycle of Arabian mares in Egypt gave the following results:
1. The estrus cycle was as short as 12 and as long as 240 days.
2. Cycles considered as normal ranged between 16 and 34 days and were more concentrated in the period 20–26 days.
3. Periods of anestrum caused elongation of the cycles to varying lengths, from double the normal cycle period to four times or more.
4. Seasonal variations in the length of the estrus cycle are discussed.
Douglas RH, Del Campo MR, Ginther OJ.On the day of ovulation (Day 0), 20 pony mares were randomly assigned to one of five groups (4 mares/group) which were given intracarotid arterial (ICA) and intraovarian arterial (IOA) injections on Day 7 as follows: 1) vehicle ICA, vehicle IOA (control); 2) .125 mg PGF2α ICA, vehicle IOA; 3) vehicle ICA, .125 mg PGF2α IOA; 4) .250 mg PGF2α ICA, vehicle IOA; or 5) vehicle ICA, .250 mg PGF2α IOA. Peripheral plasma progesterone and LH concentrations were determined for 0 (pretreatment) and .1, .25, .50, .75, 1, 6, 12, 24, 48, 72 and 96 h posttreatment. The intervals (days) from treatment to ...
Tervit HR.Recent advances in reproductive physiology offer ways for exploiting superior, female cattle and for manipulating physiological events such as parturition. The techniques involved in these advances and their associated hazards are the subject of this review.
Serrano L, Lees P.The butyrophenone tranquilliser, azaperone, was administered intramuscularly to ponies in five series of experiments, using a dose level of 0-4 mg/kg once and 0-8 mg/kg four times. An excellent or good sedative effect was usually obtained with both dose levels, but the response was more consistent with the higher dose. The onset of sedation was apparent within 10 min of administration, the maximal effect usually occurring between 20 and 60 min while sedation was no longer apparent after 2 to 6 h. Body temperature was reduced in all animals for at least 2 h and respiratory rate was increased in...
Hillidge CJ, Lees P.The neuroleptanalgesic drug combination of
etorphine and acepromazine (Large Animal
Immobilon; Reckitt & Colman Ltd.) was
administered i.v. at the recommended dose rate
(24 ,ug/kg etorphine and 100 pg/kg acepromazine)
to twelve Welsh Mountain ponies of 185 to 336 kg
bodyweight. Cardiovascular measurements were
made before and at pre-determined times up to
30 min after the injection. The etorphine
antagonist, diprenorphine (Revivon; Reckitt &
Colman Ltd.), was then injected i.v. (30,ug/kg)
and further measurements were obtained.
Pronounced increases in heart rate, moderate
increase...
Novotny EN, Hässig M, Palme R, Fürst AE, Weishaupt MA.The Zurich's Sechseläuten is a traditional festival of the Zurich guilds, in which around 500 horses take part. After a parade through the old town of Zurich, the riders gather at a big square to canter around a burning woodpile topped with an exploding effigy (the «Böögg»). The level of stress experienced by the horses partaking in this event is subjected to increasing scrutiny. The aim of this study was to evaluate the stress load of the horses participating in the Sechseläuten procession more objectively by measuring heart rate and faecal cortisol metabolites. Twenty-three horse-rider...
Colavizza M, Hervagault JF.After extraction and purification, the kinetic behavior of the Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) from horse brain was investigated as a function of ATP and a synthetic substrate, syntide-2. Both phospho- and dephospho- forms of the enzyme obey a bi-bi random mechanism. The K(M)s for ATP (K(M,ATP)) and syntide-2 (K(M,syntide-2)) were determined as equal to 80 and 30 microM, respectively. However, the maximum reaction yield is decreased by 50% when the enzyme is (auto)phosphorylated. In addition, this phosphorylated form of the enzyme leads to the formation of a total...
Gaynor JS, Bednarski RM, Muir WW.The effect of xylazine on the arrhythmogenic dose of epinephrine (ADE) was studied in 9 horses. Anesthesia was induced by administration of guaifenesin (50 mg/kg of body weight, IV) followed by thiamylal (4 to 6 mg/kg, IV) and was maintained at 1 minimal alveolar concentration (MAC) of halothane (0.89%). Base apex ECG and facial artery pressure were recorded. Epinephrine was infused in a sequence of arithmetically spaced increasing rates (initial rate 0.25 micrograms/kg/min) for a maximum of 10 minutes. The ADE was defined as the lowest epinephrine infusion rate to the nearest 0.25 micrograms/...
Thompson DL, Reville-Moroz SI, Derrick DJ, Walker MP.Sixteen intact cyclic mares were treated on the fourth day of estrus and then every other day for a total of six injections with 1) testosterone propionate, 2) dihydrotestosterone (DHT) benzoate, 3) estradiol (E2) benzoate or 4) safflower oil. Mares were given gonadotropin releasing hormone (GnRH) on Day 3 of estrus (pretreatment) and again 24 h after the last steroid or oil injection. Treatment with testosterone propionate resulted in a greater (P less than 0.05) follicle-stimulating hormone (FSH) response to the second injection of GnRH compared with all other treatments. Treatment with DHT ...