Metabolic response of horses to a high soluble carbohydrate diet: effects of low-intensity submaximal exercise and sodium bicarbonate supplementation.

Four mares fed a low fiber, high soluble carbohydrate diet were used in a crossover design to evaluate the effects of dietary sodium bicarbonate (NaHCO3) supplementation during daily low-intensity submaximal working conditions. Mares were fed the diet at 1.7 times the maintenance energy requirement for mature horses at work. The horses tolerated the diet well and had no clinical abnormalities. Resting venous blood bicarbonate (HCO3), standard HCO3, and base excess (BE) concentrations significantly (P less than 0.05) increased with NaHCO3 supplementation, but no significant changes in resting venous blood pH or carbon dioxide tension (PCO2) were recorded. Venous blood HCO3, standard HCO3, BE, hemoglobin, and heart rate were significantly (P less than 0.05) increased and plasma lactate concentration was significantly (P less than 0.05) decreased in the control horses and in the horses given the NaHCO3 supplement during low-intensity submaximal exercise. There were no significant changes in venous blood pH, PCO2, or plasma protein concentration with exercise. Venous blood HCO3, standard HCO3, and BE concentrations were significantly (P less than 0.05) greater during submaximal exercise in horses given the NaHCO3 supplement. There were no significant differences in plasma lactate or total protein concentrations, blood pH, PCO2, or hemoglobin concentration between the 2 groups during exercise.     

Effect of sodium bicarbonate on racing Standardbreds

Twenty-two Standardbred horses in race training were used in a crossover experiment to determine the effect of oral sodium bicarbonate (NaHCO3) administration on performance and metabolic responses to a 1.6-km (1-mile) race. Horses were paired and one horse in each pair was treated with either NaHCO3 (300 mg/kg BW) or a placebo, 2.5 h before they raced against each other. Each horse was scheduled to compete in two races, approximately 1 wk apart, one on each treatment. Horses always raced in the same pairs. Fourteen horses successfully completed both races. Jugular blood samples were obtained 1.5 h after treatment (rest), immediately before racing, 5 min post-race and 15 min post-race. In six horses, blood samples also were obtained 30 min post-race. Race times averaged 1.1 s faster after NaHCO3 treatment (P less than .1). Sodium bicarbonate treatment also elevated blood pH (P less than .05). In the horses sampled 15 and 30 min post-race, blood lactate disappearance was faster with the NaHCO3 treatment (P less than .05). The NaHCO3 may delay the fatigue precipitated by i.m. acidosis. Because other factors may limit performance (musculoskeletal soundness, cardiovascular and respiratory ability), NaHCO3 would not be expected to enhance the performance of all horses. However, the effect of NaHCO3 on lactate clearance may have implications for all intensively worked horses; because lactate and the associated hydrogen ions are believed to cause muscle damage and soreness, any mechanism to increase their removal rate could benefit the equine athlete.     

Furosemide and sodium bicarbonate-induced alkalosis in the horse and response to oral KCl or NaCl therapy

Metabolic alkalosis was induced in 10 clinically normal horses by administration of furosemide (1 mg/kg of body weight, IM) followed 4.5 hours later by sodium bicarbonate (NaHCO3; 500 g in 8 L water) via nasogastric tube. Furosemide diuresis resulted in a mean weight loss of 21.1 kg, which was associated with small, but significant, increases in venous blood pH, bicarbonate, and plasma protein concentrations (P less than 0.001), while plasma potassium, chloride, and calcium concentrations declined significantly (P less than 0.001). Oral administration of the hypertonic NaHCO3 solution resulted in clinical evidence of hypovolemia, which was accompanied by a marked increase (P less than 0.001) in plasma protein concentration. Seven of the 10 horses developed signs of neuromuscular excitability, as evidenced by muscle fasciculations, and 5 of the horses developed diaphragmatic flutter. Hypernatremia was transiently induced, but it resolved as the horses were allowed access to water. The alkalosis induced by furosemide and NaHCO3 was profound and persisted for a 24-hour period and was associated with marked hypochloremia and hypokalemia. Partial replacement of the electrolyte deficits and correction of the metabolic alkalosis was attempted, using 1,000 mEq of NaCl or KCl given as an isotonic solution via nasogastric tube. In the KCl-treated group, there was a prompt and significant decline in venous blood pH and bicarbonate concentration (P less than 0.001) accompanied by a significant increase in plasma potassium concentration (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Acid-base and electrolyte balance in dairy heifers fed forage and concentrate rations: effects of sodium bicarbonate

Eight Holstein heifers were fed diets of alfalfa hay, corn silage, or finely ground corn grain with or without NaHCO3 in a rotating experimental design. Acid-base status and renal excretion of electrolytes were evaluated during short-term (1 and 5 day) and long-term (24 day) feeding trials. Heifers fed alfalfa hay had a greater metabolic buffering capacity than did heifers fed corn silage. Heifers fed grain had lower blood pH and bicarbonate values than did those fed the forage diets. The most pronounced effects of grain-feeding were aciduria and phosphaturia. Aciduria did not occur when NaHCO3 was added to the grain at 2% of the ration on a dry matter basis. Grain-fed heifers had significantly (P less than 0.05) lower blood and urine pH and bicarbonate values, and excreted significantly more calcium, phosphorus, and magnesium in the urine than did those fed grain plus NaHCO3. Sodium bicarbonate, as a 2% dietary supplement, counteracted many effects of high-grain diets.     

Physiological responses in swine treated with water containing sodium bicarbonate as a prophylactic for gastric ulcers

Maintenance of gastric pH above 4.0 aids the prevention of bile acid-mediated ulcerative damage to the pars esophageal tissue in pigs. One means of doing so is the addition of buffering compounds, such as sodium bicarbonate, to the water supply; however, any potential physiological effect of buffer consumption has yet to be determined. Experiment 1 tested the acute effects of buffer addition to the water supply on systemic acid-base and electrolyte balance in swine (BW 40.7 +/- 3.0 kg). Consumption of water calculated to a 200 mOsm solution with sodium bicarbonate for 24 h increased (P < 0.05) blood Na+, HCO3(-), and pCO2, although these effects were all within physiologically tolerable levels. Urine pH and Na+ excretion increased (P < 0.001) following the consumption of NaHCO3, with Na+ concentration almost threefold higher in treated pigs compared with controls. Experiment 2 determined the chronic systemic effects of buffer consumption by measuring blood and urine variables, with pigs consuming NaHCO3-treated water throughout. Water consumption increased (P < 0.001) during buffer consumption, although intake levels remained within normal ranges. Blood pH levels were not affected by long-term consumption of dietary buffer; however, blood HCO3(-) (P < 0.05), Na+, and pCO2 (P < 0.01) increased. Urine pH and urine Na+ concentration increased (P < 0.01) in buffer-treated compared with control animals. Results indicate that sodium bicarbonate can safely be added to the water supply for pigs, with no clinically relevant alterations in acid-base balance because the animals readily compensate for buffer intake.     

Haematological, serum electrolyte and blood gas effects of small volume hypertonic saline in experimentally induced haemorrhagic shock

The effects of treatment with small volume hypertonic (2400 mOsm/litre) and isotonic (300 mOsm/litre) saline on serum electrolyte and biochemical concentrations, haemograms and blood gases were evaluated in 12 horses using a haemorrhagic shock model. Intravascular catheters were placed surgically for sample collection prior to anaesthesia. Controlled haemorrhage was initiated and continued until mean systemic pressure reached 50 to 60 mmHg. Hypertonic or isotonic saline (2 litres) was administered by intravenous infusion and data collected for 2 h. Following haemorrhage, packed cell volume (PCV), haemoglobin, blood glucose concentrations and erythrocyte numbers increased whereas plasma total protein and albumin concentrations decreased. Infusion of hypertonic saline resulted in a further decrease in total protein and albumin concentrations. Glucose concentrations and other haematological variables were unaffected. Isotonic saline administration did not affect electrolyte, total protein or albumin concentrations. Concentrations of sodium and chloride were unaffected by hypotension but increased significantly following hypertonic saline treatment, exceeding normal values during the immediate post treatment period. Serum osmolality increased concurrently. No significant changes in arterial and venous blood gas values were observed with haemorrhage or isotonic saline treatment. A transient decrease in arterial and venous blood pH and a sustained decrease in venous bicarbonate and base excess concentrations occurred following hypertonic saline administration. No significant increases in any serum biochemical concentrations occurred during hypotension or following infusion of either isotonic or hypertonic saline. These results demonstrate that small volume hypertonic saline can be administered safely to horses without producing extreme changes in electrolyte concentrations, blood gases or haematological parameters.     

Partial pressures of oxygen and carbon dioxide, pH, and concentrations of bicarbonate, lactate, and glucose in pleural fluid from horses

Samples of pleural fluid from 20 horses with effusive pleural diseases of various causes were evaluated; samples from 19 horses were used for the study. There were differences for pH (P = 0.001) and partial pressure of oxygen (PO2) between arterial blood and nonseptic pleural fluid (P = 0.0491), but there were no differences for pH, PO2, partial pressure of carbon dioxide (PCO2), and concentrations of bicarbonate (HCO3-), lactate, and glucose between venous blood and nonseptic pleural fluid. Paired comparisons of venous blood and nonseptic pleural fluid from the same horse indicated no differences. There were differences (P = 0.0001, each) for pH, PO2, PCO2, and concentrations of HCO3- between arterial blood and septic pleural fluid. Differences also existed for pH (P = 0.0001), PCO2 (P = 0.0003), and concentrations of HCO3- (P = 0.0001), lactate (P = 0.0051), and glucose (P = 0.0001) between venous blood and septic pleural fluid. Difference was not found for values of PO2 between venous blood and septic pleural fluid, although 4 samples of septic pleural fluid contained virtually no oxygen. Paired comparisons of venous blood and septic pleural fluid from the same horse revealed differences (P less than 0.05) for all values, except those for PO2. These alterations suggested functional and physical compartmentalization that separated septic and healthy tissue. Compartmentalization and microenvironmental factors at the site of infection should be considered when developing therapeutic strategies for horses with septic pleural disease.     

Acid-base balance parameters and a value of anion gap of arterial and venous blood in Małopolski horses

The comparative study of the acid-base balance (ABB) parameters has been performed on 20 clinically healthy mature Ma?opolski horses. An arterial blood sample from the facial artery and a sample of venous blood from the external cervical vein were colected from each animal. In the samples tested, the blood pH, pCO2, tCO2, HCO3-, concentration of Na+, K+, Cl-, and a value of the anion gap were determined. The difference among pCO2, tCO2, and HCO3- in both samples tested was statistically significant, whereas the pH of the arterial blood and the pH of the venous blood did not differ significantly. The anion gap in both types of blood did not differ significantly. Conclusions: 1) ABB parameters such as pCO2, HCO3-, and tCO2 determined in the arterial and venous blood of the Ma?opolski horses differ from each other significantly. 2) In spite of the lack of the differences between pH of the arterial and venous blood, the ABB parameters in horses should be determined in the arterial blood, because the comparative study performed proves that the analysis of the ABB parameters determined for the venous blood of a healthy horse may lead to a wrong diagnosis of the compensated respiratory acidosis. 3) The mean value of anion gap in horses aged 8-12 years amounts to 20.9 mmol/l for the arterial blood and 19.93 for the venous blood; the difference between the two values is not statistically significant.     

Titrimetric determination of muscle buffering capacity (beta mtitr) in biopsy samples

In vitro titration of muscle homogenates has been used to assess muscle buffering capacity (beta mtitr) in a variety of species. In the present study, factors likely to affect the estimation of beta mtitr were investigated. Also, values of beta mtitr from normal Thoroughbred horses are presented. A non-linear titration curve was obtained with addition of HCl to muscle homogenates. As a result, beta mtitr is expressed as the mumol H+ required to change the pH of 1g of dry muscle or wet muscle from 7.1 to 6.5. An effect of dilution on the initial pH was found below 40 mg wet muscle per ml homogenising reagent (10 mg dry muscle per ml) and on beta mtitr below 10 mg wet muscle. As a result, 40 mg wet muscle or 10 mg dry muscle per ml was chosen as the minimum concentration for determination of beta mtitr. Incubation of homogenates up to 60 mins did not affect beta mtitr significantly. As a mean, beta mtitr in wet muscle was approximately 25 per cent higher compared to dry muscle. The beta mtitr of dry muscle was increased by approximately 18 per cent when HCO3- was added in an amount equivalent to the calculated HCO3- content of wet muscle at rest. The homogenisation process resulted in complete loss of adenosine triphosphate and phosphocreatine with only small changes in adenosine diphosphate and adenosine monophosphate. It was concluded that the estimates of beta mtitr did not include any contribution from 'dynamic' buffering via rephosphorylation of adenosine diphosphate by phosphocreatine, and in dry muscle it was accounted for mainly through physico-chemical buffering by phosphates, proteins and dipeptides. beta mtitr determined in biopsy samples of muscle from 20 Thoroughbred horses ranged from 100.8 to 131.8 mumol H+/g dry muscle pH 7.1 to 6.5 (mean 121.2, sd +/- 7.4).     

Accuracy and precision of the portable StatPal II and the laboratory-based NOVA stat profile 1 for measurement of pH, P(CO2), and P(O2) in equine blood

OBJECTIVE: To investigate the accuracy and precision of the portable, battery-powered StatPal II and the laboratory-based NOVA StatProfile 1 blood gas and pH analyzers for use in analysis of equine blood. STUDY DESIGN: Patient sample comparison and whole blood tonometry. SAMPLE POPULATION: Patient sample comparison: 125 arterial or venous blood samples from 49 healthy, awake, or anesthetized horses or ponies. Tonometry: venous blood samples from 11 healthy Thoroughbred horses. MATERIALS AND METHODS: Arterial and venous blood taken from awake and anesthetized equine patients was placed in an ice-water bath, then analyzed within 30 minutes of collection. Bias and limits of agreement between analyzers in measurement of pH, P(CO2), and P(O2) were calculated according to the method of Bland and Altman. Tonometry, using analyzed gases with a range of P(O2) of 28 to 286 mm Hg and P(CO2) of 21 to 85 mm Hg, was performed on equine whole blood or blood with abnormally high (55%) or low (20%) hematocrit. Samples were introduced directly from the tonometer into the analyzers. Inaccuracy (% of target value) and imprecision (coefficient of variation) were determined for each instrument. In addition, results of analysis of blood samples introduced into the analyzers at 36 degrees C, 0 to 3 degrees C, and 22 degrees C were compared. RESULTS: In the patient sample comparisons, bias between analyzers (StatPal-NOVA) for measurement of P(O2) less than 60 mm Hg was -0.33+/-6.2 mm Hg (x +/-2 SD) and for P(O2) between 60 and 110 mm Hg bias was -1.48+/-9.2 mm Hg. Bias was 46.5+/-67 mm Hg (significantly different from bias at the lower P(O2) levels) for measurement of P(O2) values of 111 to 505 mm Hg, and at P(O2) values greater than 110 mm Hg, bias increased with increasing P(O2). During the course of the study, a significant shift in bias between instruments occurred for P(CO2) and pH measurement, coincident with a change of P(CO2) and pH electrodes in the NOVA and use of a new lot of StatPal sensors. Bias (StatPal-NOVA) for P(CO2) before and after the electrode change was -3.74+/-4.2 and -0.88+/-6.8 mm Hg, and bias for pH before and after the electrode change was 0.026+/-0.034 and -0.024+/-0.038. The change in bias was significant (P<.05). In the whole blood tonometry trials, mean recovered values of P(CO2) and P(O2) from blood with a normal hematocrit ranged from 94% to 109% of target values for StatPal and from 98% to 107% for NOVA. Imprecision ranged from 3.3% to 5.3% for StatPal and from 2.2% to 4.3% for NOVA. With extremes of hematocrit (55% and 20%), StatPal's mean recovered P(CO2) values were 115% and 112% of the target value of 21 mm Hg, whereas NOVA's recovered P(CO2) values were similar to those recovered from samples with normal hematocrit. Introduction of cold blood samples (0 to 3 degrees C) into StatPal resulted in P(CO2) readings that were approximately 2 mm Hg lower than those of 22 degrees C and 36 degrees C samples (P<.05). No other effects of sample temperature were found for either instrument. CONCLUSIONS: StatPal and NOVA are of similar accuracy and demonstrate acceptable precision for measurement of P(CO2) and P(O2) in equine blood with values in the normal arterial and venous range. Mean recovered values during tonometry differed by as much as 10% between instruments, indicating that they should not be used interchangeably for a single patient or for a group of subjects in a research setting. CLINICAL RELEVANCE: The StatPal is a portable blood gas analyzer of acceptable accuracy and precision, for clinical or investigational work in horses.     

A Portable Blood Gas Analyzer for Equine Venous Blood

Evaluation of a portable blood gas analyzer, (StatPal II, Unifet, Inc, La Jolla, CA) was performed using tonometered solutions and equine blood. Samples were analyzed by the StatPal II and either an Instrument Laboratory IL1306 (Lexington, MA) or a Radiometer ABL50 blood gas analyzer (Radiometer America Inc., Westlake, OH). Comparison of the StatPal II and the IL1306 was done by analysis of 3 tonometered solutions (acidic, normal, and alkalotic) and 27 equine venous blood samples. Blood pH, Pco₂, Po₂, and [HCO₃^-] values were altered by IV infusion of 5% sodium bicarbonate or exercising the horses on a treadmill. Comparison of the StatPal II and the Radiometer was performed by analysis of 78 blood samples collected from Standard-bred horses before a race. Data were analyzed for the venous blood samples using a paired two-tailed Student's t test and Bland-Altman plots, with significance set at P < .05. The coefficients of variation for pH, Pco₂, Po₂, and [HCO₃^-] values of the tonometered solutions analyzed by the StatPal II ranged from 0.067% to 0.087%, 2% to 3.21 %, 1.21 % to 2.67%, and 0.267% to 0.828%, respectively. Comparison of the equine blood samples analyzed by the StatPal II and the IL1306 demonstrated statistically significant, but clinically irrelevant differences in pH, Pco₂, and Po₂, but not [HCO₃^-]. There were statistically significant, but clinically irrelevant differences between the StatPal II and the Radiometer for pH, Pco₂, and [HCO₃^-], but not for Po₂-It is concluded that the StatPal II provides reproducible and acceptable analysis of equine venous blood gas samples.     

The effect of colic on oxygen extraction in horses

Blood oxygen transport and oxygen extraction were assessed in horses with colic. A gravity score (GS) ranging from 1 to 3 was attributed to each colic case with healthy horses used as controls. Jugular venous and carotid arterial blood samples were collected and concentrations of 2,3-diphosphoglycerate, adenosine triphosphate, inorganic phosphate and chloride were determined. pH and partial pressures of carbon dioxide (PCO(2)), and oxygen (PO(2)) were also measured. Oxygen equilibrium curves (OEC) were constructed under standard conditions and oxygen extraction ratios calculated. Haemoglobin oxygen affinity measured under standard conditions (P50(std)) was unchanged in colic horses compared with healthy controls. Horses with the highest GS, i.e. 3 had lower blood pH values than healthy animals. Arterial and venous partial pressures of oxygen at 50% haemoglobin saturation (P50(a) and P50(v)) were significantly higher in horses suffering from colic (GS=3) than in healthy horses. The oxygen extraction ratio was also significantly increased in colic horses with a GS of 3. A rise in the oxygen extraction ratio detected in the most severely affected animals seemed to reflect the compensatory properties of the oxygen transport system where extraction of oxygen from the blood increases when systemic oxygen delivery decreases, as might be anticipated in horses with colic.     

Mixed venous oxygen tension as an estimate of cardiac output in anesthetized horses

The relationship between mixed venous O2 tension and cardiac output was studied in six anesthetized horses breathing 100% O2. Cardiac output, O2 consumption, mean arterial pressure, heart rate, and arterial and venous blood gases were measured after administration of xylazine or dobutamine to horses in lateral, sternal, and dorsal recumbencies. After approximately 3 hours, Escherichia coli endotoxin was administered while horses were in dorsal recumbency, and all measurements were repeated. Relationships between cardiac index (CI) and PVO2, heart rate, mean arterial pressure, jugular PVO2, and PVO2 of blood from a superficial limb vein were evaluated by linear regression analysis. Mean arterial pressure was significantly (P less than 0.05) correlated with CI in horses in all positions and after endotoxin administration. However, data points were poorly grouped. Heart rate and CI were significantly correlated in horses in all positions, but not after endotoxin administration. Correlations between jugular PVO2 and PVO2 of blood from a superficial limb vein were not significant in horses in sternal recumbency, and PVO2 of blood from a superficial limb vein was not significantly correlated with CI in horses in lateral recumbency. There was a significant and tight correlation between PVO2 and CI in horses in all positions and after endotoxin administration.     

Trona and sodium bicarbonate in beef cattle diets: effects on pH and volatile fatty acid concentrations

A study was conducted to evaluate the effectiveness of NaHCO3 and trona in beef cattle diets. Trace element (n = 28) analysis revealed no toxicological or safety concerns with the use of trona. Trona was more (P less than .05) soluble in ruminal fluid than Na2CO3, and NaHCO3 and had greater (P less than .05) buffering capacity (9.6 meq/g) than NaHCO3 (6.1 meq/g) but less (P less than .05) than Na2CO3 (11.1 meq/g). Calcium carbonate was insoluble and did not buffer ruminal fluid. Six yearling (avg 272 kg) Hereford X Angus steers, each with ruminal, duodenal and ileal cannulas, were fed 50:50 (cracked corn-based concentrate:cottonseed hulls) or 90:10 concentrate diets with no buffer, 1% NaHCO3 or with 1% trona. Intake, across all treatments, averaged 2.4% of body weight. Propionate (mmol/liter) increased (17.6 vs 13.5; P less than .05) and butyrate decreased (3.5 vs 5.2; P less than .05) with trona in the 90:10 diet as compared with no buffer. Propionate (16.8) increased (P less than .05) with NaHCO3 in the 90:10 diet. Average ruminal pH was greater (P less than .05) in 90:10 diets with trona or NaHCO3 than with no buffer (5.61, 5.61 vs 5.55); duodenal pH was greater (P less than .01) with trona than with no buffer (2.66 vs 2.55). Trona reduced ruminal pH-hours (P less than .05) and pH-area (P less than .12; time and area below mean pH of control) below control for both concentrate levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of nasogastric administration of sodium bicarbonate on carbon 13 isotopic enrichment of carbon dioxide in serum of horses

OBJECTIVE: To determine the effect of administration of commercially available sodium bicarbonate (NaHCO3) on carbon 13 (13C) isotopic enrichment of carbon dioxide (CO2) in serum of horses. ANIMALS: 7 healthy Thoroughbreds. PROCEDURES: Sodium bicarbonate (450 g) was administered via nasogastric intubation to horses. Horses had been fed a diet obtained from the same source and had access to water from the same source for 3 months before the study. Blood samples were collected immediately before and at 2, 4, 6, and 24 hours after administration of NaHCO3. The concentration of total CO2 in serum was measured by use of a commercial analyzer. The 13C enrichment of bicarbonate in serum was estimated by measurement of 13C enrichment of CO2 released by acidification of the serum. The 13C enrichment of commercially available NaHCO3 was also determined and compared with that of CO2 in serum of horses before administration of NaHCO3. RESULTS: Commercially available NaHCO3 had a 13C enrichment significantly different from that of carbon dioxide in serum of horses before treatment. Administration of NaHCO3 increased the concentration of total CO2 from pretreatment values. The 13C enrichment of CO2 in serum was only transiently and minimally affected after administration of NaHCO3. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of NaHCO3 was not detected by measuring 13C enrichment of CO2 in serum of horses.     

Effects of enalaprilat on cardiorespiratory, hemodynamic, and hematologic variables in exercising horses.

OBJECTIVE: To determine the effects of IV administration of enalaprilat on cardiorespiratory and hematologic variables as well as inhibition of angiotensin converting enzyme (ACE) activity in exercising horses. ANIMALS: 6 adult horses. PROCEDURE: Horses were trained by running on a treadmill for 5 weeks. Training was continued throughout the study period, and each horse also ran 2 simulated races at 120% of maximum oxygen consumption. Three horses were randomly selected to receive treatment 1 (saline [0.9% NaCl] solution), and the remaining 3 horses received treatment 2 (enalaprilat; 0.5 mg/kg of body weight, IV) before each simulated race. Treatment groups were reversed for the second simulated race. Cardiorespiratory and hematologic data were obtained before, during, and throughout the 1-hour period after each simulated race. Inhibition of ACE activity was determined during and after each race in each horse. RESULTS: Exercise resulted in significant increases in all hemodynamic variables and respiratory rate. The pH and PO2 of arterial blood decreased during simulated races, whereas PCO2 remained unchanged. Systemic and pulmonary blood pressure measurements and arterial pH, PO2, and Pco2 returned to baseline values by 60 minutes after simulated races. Enalaprilat inhibited ACE activity to < 25% of baseline activity without changing cardiorespiratory or blood gas values, compared with horses administered saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: Enalaprilat administration almost completely inhibited ACE activity in horses without changing the hemodynamic responses to intense exercise and is unlikely to be of value in preventing exercise-induced pulmonary hemorrhage.     

补喂芒柄花素对伊犁马1000 m速度赛成绩、血气及抗氧化指标的影响

【目的】研究芒柄花素对伊犁马1 000 m速度赛成绩、血气及抗氧化指标的影响,为伊犁马运动训练过程中营养补喂剂的研发提供参考依据。【方法】试验选择平均体重(411 kg±29 kg)、平均年龄(2.0岁±0.50岁)、1 000 m速度赛成绩(135.24 s±15.75 s)相近并且健康状况良好的12匹伊犁马公马作为研究对象,随机分为对照组与试验组,每组6匹。在相同的饲养管理、饲粮营养水平及运动训练条件下,试验组每匹马每天补喂芒柄花素8 g,进行为期30 d的补喂试验。在试验第30天进行1 000 m速度赛,记录比赛成绩并在赛后即刻通过颈静脉采集血样,使用血气分析仪测定电解质水平、酸碱平衡及血气指标,使用试剂盒测定抗氧化指标。【结果】补喂芒柄花素能够显著缩短伊犁马1 000 m速度赛比赛用时(P<0.05);对血浆中电解质水平、酸碱平衡及血气相关指标均无显著影响(P>0.05);在血浆抗氧化指标方面,补喂芒柄花素能够显著提高赛后马匹血浆中超氧化物歧化酶、过氧化氢酶和总抗氧化能力,分别比对照组提高了11.12%(P<0.05)、8.45%(P<0.05)和32....     

Surface oximetry of healthy and ischemic equine intestine

Measurements of jejunal, ileal, and large colon (pelvic flexure) surface O2 tension (PSO2) were made in halothane-anesthetized horses with a nonheated miniature oxygen polarographic electrode. Assisted ventilation with 100% O2 was used to maintain PaCO2 tension at 50 +/- 8 mm of Hg while mean arterial blood pressure was maintained greater than or equal to 70 mm of Hg. Mean +/- SD PSO2 for the intestinal segments were: jejunum (horses 1 to 4), 71 +/- 20 mm of Hg; ileum (horses 1 to 4), 61 +/- 8 mm of Hg; and pelvic flexure of the large colon (horses 1 to 10), 55 +/- 13 mm of Hg. The response of the sensor to intestinal ischemia was studied in the large colon of an additional 12 halothane-anesthetized horses, using 4 types of vascular occlusion: venous (4 horses); arterial and venous (4 horses); venous and intramural vascular obstruction (2 horses); and arterial, venous, and intramural obstruction (2 horses). Venous and arterial occlusions were maintained for 30, 60, 90, and 120 minutes, whereas intramural obstruction combined with either type of vascular obstruction was studied for 60 to 120 minutes. After vascular occlusion, PSO2 decreased to 8 +/- 7 mm of Hg for venous obstruction, 4 +/- 3 mm of Hg for arterial and venous obstruction, 6 +/- 0 mm of Hg for intramural and venous obstruction, and 3 +/- 0 mm of Hg after intramural and arterial and venous obstruction. Thirty minutes after release of the clamps, the PSO2 increased to greater than or equal to 50% of the preoccluded large colon value.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determinants of oxygen delivery and hemoglobin saturation during incremental exercise in horses

OBJECTIVE: To determine components of the increase in oxygen consumption (VO2) and evaluate determinants of hemoglobin saturation (SO2) during incremental treadmill exercise in unfit horses. ANIMALS: 7 unfit adult mares. PROCEDURES: Horses performed 1 preliminary exercise test (EXT) and 2 experimental EXT. Arterial and mixed venous blood samples and hemodynamic measurements were taken during the last 30 seconds of each step of the GXT to measure PO2, hemoglobin concentration ([Hb]), SO2, and determinants of acid-base state (protein, electrolytes, and PCO2). RESULTS: Increased VO2 during exercise was facilitated by significant increases in cardiac output (CO), [Hb], and widening of the arteriovenous difference in O2. Arterial and venous pH, PaO2, and PvO2 decreased during exercise. Arterial PCO2, bicarbonate ([HCO3-])a, and [HCO3-] decreased significantly, whereas PVCO2 and increased. Arterial and venous sodium concentration, potassium concentration, strong ion difference, and venous lactate concentration all increased significantly during exercise. CONCLUSIONS AND CLINICAL RELEVANCE: Increases in CO, [Hb], and O2 extraction contributed equally to increased VO2 during exercise. Higher PCO2 did not provide an independent contribution to shift in the oxyhemoglobin dissociation curve (OCD) in venous blood. However, lower PaCO2 shifted the curve leftward, facilitating O2 loading. The shift of ODC resulted in minimal effect on O2 extraction because of convergence of the ODC at lower values of PO2. Decreased pH appeared responsible for the rightward shift of the ODC, which may be necessary to allow maximal O2 extraction at high blood flows achieved during exercise.     

Effects of dietary cation-anion balance on acid-base status in horses

Four mature, sedentary geldings were used in a 4x4 Latin square design experiment to study the effects of dietary cationanion balance (DCAB), defined as meq ((Na + K) - C1)/kg of dietary dry matter, on urine pH, blood pH and blood gasses. Four diets with actual DCAB levels of +21 (Low, L), +125 (Medium Low, ML), +231 (Medium High, MH) and +350 (High, H) were fed for a 21-day adjustment period and a 72 hour collection period. Total urine output was collected every 4 hours post feeding for 72 hours, and like times across days were combined for analyses. Arterial and venous blood samples were drawn, via indwelling catheters, hourly for 12 hours beginning at feeding. All samples were analyzed immediately after collection for pH, blood gasses and blood acid-base measures. Urine pH was lower (p<.05) at all measured intervals when geldings consumed diet L than when they consumed diets MI, MH and H. Least squares means for urine pH ranges from 5.40 to 5.86 on diet L, 6.79 to 7.30 on diet ML, 7.35 to 7.63 on diet MH and 7.52 to 8.14 on diet H. Blood pH, pCO₂ and HCO₃ values were also significantly lower in both arterial and venous samples when geldings consumed diet L than when fed diets MH and H. Results of this trial indicate that horses consuming highly anionic diets may experience a nutritionally-induced metabolic acidosis.