• View in gallery

    Rectal temperature measured in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 4 field trials conducted at ambient temperatures of 2.2° to 29.4°C. Body temperatures were measured by use of an ear thermometer during test 2; those values are not presented. The number of dogs from which data were collected varied among tests; at tests 1 through 5, data were obtained from 9, 10, 6, 6, and 5 dogs, respectively. Four dogs were assessed at a single test, 8 dogs were assessed at 2 tests, 2 dogs were assessed at 3 tests, and 2 dogs were assessed at all 5 tests. Overall, there were 36 data collections. The dotted line is the mean baseline value.2 In instances where 2 dogs had the same value, the symbol is shaded gray. Values for 2 dogs that developed a single episode of heat stress at the final trial held on the hottest day are superimposed in the dashed rectangle; data for these dogs are indicated by white or black triangles (dogs 1 and 2, respectively).

  • View in gallery

    Venous blood pH measured in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 5 field trials conducted at ambient temperatures of 2.2° to 29.4°C. The dotted line is the mean baseline value. Values measured at the 2 field trials conducted at ambient temperatures > 21°C (within oval outline) are significantly (P < 0.001) higher than values measured at trials conducted at ambient temperatures b 21°C. Values of pHv < 7.100 and > 7.600 are considered critical care alert values; dogs in which such values are detected require immediate attention or therapeutic intervention.c See Figure 1 for remainder of key.

  • View in gallery

    Values of PvCO2 in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 5 field trials conducted at ambient temperatures of 2.2° to 29.4°C. The dotted line is the mean baseline value. Values measured at the 2 field trials conducted at ambient temperatures > 21°C (within oval outline) are significantly (P < 0.001) lower than values measured at trials conducted at ambient temperatures b 21°C. See Figure 1 for remainder of key.

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Respiratory alkalosis and primary hypocapnia in Labrador Retrievers participating in field trials in high–ambient-temperature conditions

Janet E. Steiss DVM, PhD1 and James C. Wright DVM, PhD2
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  • 1 Department of Anatomy, Physiology, and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.
  • | 2 Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849.

Abstract

Objective—To determine whether Labrador Retrievers participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures.

Animals—16 Labrador Retrievers.

Procedures—At each of 5 field trials, 5 to 10 dogs were monitored during a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]; 36 assessments); ambient temperatures ranged from 2.2° to 29.4°C. For each dog, rectal temperature was measured and a venous blood sample was collected in a heparinized syringe within 5 minutes of test completion. Blood samples were analyzed on site for Hct; pH; sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; and values of PvO2 and PvCO2. Scatterplots of each variable versus ambient temperature were reviewed. Regression analysis was used to evaluate the effect of ambient temperature (≤ 21°C and > 21°C) on each variable.

Results—Compared with findings at ambient temperatures ≤ 21°C, venous blood pH was increased (mean, 7.521 vs 7.349) and PvCO2 was decreased (mean, 17.8 vs 29.3 mm Hg) at temperatures > 21°C; rectal temperature did not differ. Two dogs developed signs of heat stress in 1 test at an ambient temperature of 29°C; their rectal temperatures were higher and PvCO2 values were lower than findings in other dogs.

Conclusions and Clinical Relevance—When running distances frequently encountered at field trials, healthy Labrador Retrievers developed hyperthermia regardless of ambient temperature. Dogs developed respiratory alkalosis and hypocapnia at ambient temperatures > 21°C.

Physical challenges for Labrador Retrievers running field trials are different than those for dogs engaged in sports such as Greyhound racing. In field trials, Labrador Retrievers frequently run in warm weather for 5 to 10 minutes over distances approaching a mile or more, with the additional mental task of locating the fallen birds.

In 1999, Matwichuk et al1 reported rectal temperature and hematologic, biochemical, and blood gas and acid-base values for 14 healthy Labrador Retrievers after they completed a 10-minute retrieving drill. Those investigators detected significantly increased rectal temperature, arterial blood pH, and PaO2 and significantly decreased PaCO2 and arterial blood bicarbonate concentration immediately after exercise. Subsequently, our laboratory reported values for healthy Labrador Retrievers during training and after completion of land retrieving tests at a field trial.2 The findings of that study confirmed that increases in rectal temperature and pHv and a decrease in venous PCO2 develop in association with this form of exercise.

In their report, Matwichuk et al1 stated that ambient temperature did not affect rectal temperature in dogs during the retrieving drill. Ambient temperatures in that study ranged from 11° to 28°C. In the other study,2 ambient temperatures were within a narrow range of 23° to 26°C. Again, no effect of ambient temperature on rectal temperature was apparent. The purpose of the study reported here was to assess physiologic effects of field trial exercise in dogs in a wider range of ambient temperatures. In particular, the intent was to determine whether dogs participating in field trials develop respiratory alkalosis and hypocapnia primarily in conditions of high ambient temperatures.

Materials and Methods

Field trial dogs—The study was approved by the Animal Care and Use Committees at Tuskegee University (2002 through 2003) and Auburn University (2004). The sample group consisted of 16 Labrador Retrievers (5 sexually intact females and 11 sexually intact males; age range, 4 to 8 years) that were engaged in field trial competition with 1 professional trainer. Dogs were considered healthy on the basis of history, trainer's opinion, and findings of a brief physical examination. None of the dogs had a history of exercise intolerance, collapse, or intolerance to hot weather. Additionally, during the 12-month period after completion of the study, the dogs did not develop signs of exercise intolerance or intolerance of hot weather. The dogs' diet consisted of a commercial food producta formulated for performance dogs. Dogs trained a minimum of 4 d/wk; training consisted of approximately 15 minutes of vigorous exercise twice each day. At each of the 5 field trials, 5 to 10 dogs were monitored, depending on which dogs competed on specific days. Only data from dogs that completed a test were analyzed. Dogs that hunted excessively for a bird or were unable to locate the bird were not evaluated.

Clinicopathologic and physiologic measurements—Baseline measurements were obtained in the yard at the kennel on a morning before the dogs were trained and have been reported previously.2 At field trials, body temperature was measured and venous blood samples were collected from dogs within 5 minutes of completing a test. Body temperature was assessed rectally after tests 1, 3, 4, and 5 and by use of an ear thermometer after test 2. Blood (1 mL) was collected from a cephalic vein into a heparinized tuberculin syringeb for immediate analysis by use of a portable analyzer.c Quality-control procedures for this analyzer were performed as recommended by the manufacturer.3 Clinicopathologic variables assessed included Hct; plasma sodium, potassium, ionized calcium, glucose, lactate, bicarbonate, and total CO2 concentrations; PvO2; PvCO2; and pHv.

Field trial conditions—Dogs were monitored at 5 field trials that were licensed by the American Kennel Club and that took place from September 2002 to May 2004 in Georgia, Alabama, and Tennessee. The trials were numbered in chronologic order (1 through 5). Tests were land marks, meaning that the dogs retrieved birds on land with no swimming. Distances were measured with a range finderd from the line (the starting point) to the locations of the birds. The total straight-line distances (distance measured with the range finder multiplied by 2) for the tests ranged from 1,076 to 2,220 m. Terrain was flat to moderately hilly. The terrain for the tests at the 5 trials had areas of both open ground and moderately high cover (ie, high grass). Time to complete a test ranged from 5 to 10 minutes. Ambient temperatures were recorded on location and verified from data provided by an online weather service.4 The reported ambient temperature was the temperature for the time nearest noon in the city closest to the field trial location. Ambient temperatures ranged from 2.2° to 29.4°C.

Field trial dogs with heat stress—Two of the 16 dogs (dogs 1 and 2) developed transient signs of heat stress after completing the fifth and final test, which took place on the hottest day (29.4°C). Dog 1 had been included in the data collection for tests 1, 2, and 3 and dog 2 had been included in the data collection for test 2 with no evidence of heat stress. The data from these 2 dogs were not included in the analyses for test 5; however, the data obtained during the preceding tests were included in the analyses for those tests.

Statistical analysis—Data were storede electronically and analyzed by use of computer software.e,f Scatterplots of all data were examined. Data were blocked on dog to account for repeated samples that were obtained from some of the dogs. For the regression analysis, values for clinicopathologic variables and rectal temperature were the dependent variables and the ambient temperature grouping (b 21°C and > 21°C) was the independent variable. A value of P < 0.05 was considered significant.

Results

Field trials—The distance and ambient temperature of each test were as follows: test 1, 1,168 m at 26.7°C; test 2, 1,036 m at 18.0°C; test 3, 2,220 m at 8.9°C; test 4, 1,076 m at 2.2°C; and test 5, 1,338 m at 29.4°C. The number of dogs from which data were collected varied among tests; at tests 1 through 5, data were obtained from 9, 10, 6, 6, and 5 dogs, respectively. Four dogs were assessed at a single test, 8 dogs were assessed at 2 tests, 2 dogs were assessed at 3 tests, and 2 dogs were assessed at all 5 tests. Overall, there were 36 data collections.

Clinicopathologic and physiologic findings—No significant (P > 0.05) differences in rectal temperature; PvO2; and sodium, ionized calcium, and lactate concentrations were detected between the ambient temperature groupings (ie, data collected during tests at b 21°C and > 21°C [Table 1]). However, pHv was significantly higher (mean, 7.521 vs 7.349; P < 0.001) and PvCO2 was significantly lower (mean, 17.8 vs 29.3 mm Hg; P < 0.001) in dogs completing tests during warmer weather (ambient temperatures > 21°C). Scatterplots of all variables against ambient temperature were examined; plots of individual values for rectal temperature, pHv, and PvCO2 were of particular interest (Figures 1–3). Several other variables were significantly different between the ambient temperature groupings, but the values were not considered clinically important because they were either within the ranges of previously reported2 baseline values or within the laboratory reference ranges.

Table 1—

Mean ± SD (range) values of venous blood variables assessed in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 5 field trials conducted at ambient temperatures ≤ 21°C or > 21 °C (range, 2.2° to 29.4°C). The number of dogs from which data were collected varied among tests; at tests 1 through 5, data were obtained from 9, 10, 6, 6, and 5 dogs, respectively. Four dogs were assessed at a single test, 8 dogs were assessed at 2 tests, 2 dogs were assessed at 3 tests, and 2 dogs were assessed at all 5 tests. Overall, there were 36 data collections. Blood samples were collected from 2 dogs that developed heat stress during the final trial on the hottest day. Data were blocked on dogs, and the influence of temperature grouping was evaluated via regression analysis.

VariableClinically normal dogsDogs that developed heat stress
Baseline*After exercise at ambient temperatures ≤ 21 °CAfter exercise at ambient temperatures > 21 °CP valueDog 1Dog 2
Rectal temperature (°C)38.8 ± 0.240.6 ± 0.640.8 ± 0.4
(38.2–39.6)(40.0–41.6)(39.8–41.5)0.24341.941.9
pHv7.382 ± 0.0207.349 ± 0.0937.521 ± 0.088
(7.283–7.492)(7.186–7.516)(7.390–7.686)< 0.0017.6857.629
Pvco2 (mm Hg)32.6 ± 2.029.3 ± 5.017.8 ± 3.2
(25.2–42.0)(20.0–38.6)(12.9–22.9)< 0.00111.410.4
Potassium (mmol/L)4.1 ± 0.13.7 ± 0.34.0 ± 0.2
(3.7–4.6)(3.2–4.3)(3.7–4.4)0.0043.94.2
Glucose (mg/dL)94 ± 5136 ± 30112 ± 15
(85–101)(90–197)(92–143)0.014101126
Hct(%)44 ± 349 ± 443 ± 4
(39–49)(42–56)(35–48)< 0.0014243
Bicarbonate (mmol/L)19 ± 116 ± 314 + 2
(15–22)(11–21)(11–17)0.0221411
Total carbon dioxide (mmol/L)20 ± 117 ± 315 ± 2
(16–23)(12–23)(11–17)0.0091411
Sodium (mmol/L)145 ± 0.5142 ± 1.5142 ± 1.4
(143–148)(139–145)(140–145)0.700141141
Ionized calcium (mmol/L)1.28 ± 0.041.19 ± 0.061.18 ± 0.09
(1.23–1.35)(1.06–1.27)(1.13–1.26)0.6651.051.13
Lactate (mmol/L)0.90 ± 0.324.70 ± 2.803.41 ± 1.96
(0.46–1.64)(1.60–10.43)(0.95–7.86)0.2182.367.86
Pvo2 (mm Hg)36 ± 450 ± 1043 ± 12
(27–59)(37–65)(27–65)0.0883331

Baseline measurements were obtained in the yard at the dogs' kennel on a morning before training and have been reported previously.

Dogs 1 and 2 developed heat stress at the final trial; the data from these 2 dogs were not included in calculations for that test but were included for any other trials at which these 2 dogs were sampled.

Value for difference in measured variable between ambient temperature groupings (≤ 21°C and > 21°C) derived via regression analysis in which temperature grouping was the independent variable and the blood variable was the dependent variable.

Figure 1—
Figure 1—

Rectal temperature measured in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 4 field trials conducted at ambient temperatures of 2.2° to 29.4°C. Body temperatures were measured by use of an ear thermometer during test 2; those values are not presented. The number of dogs from which data were collected varied among tests; at tests 1 through 5, data were obtained from 9, 10, 6, 6, and 5 dogs, respectively. Four dogs were assessed at a single test, 8 dogs were assessed at 2 tests, 2 dogs were assessed at 3 tests, and 2 dogs were assessed at all 5 tests. Overall, there were 36 data collections. The dotted line is the mean baseline value.2 In instances where 2 dogs had the same value, the symbol is shaded gray. Values for 2 dogs that developed a single episode of heat stress at the final trial held on the hottest day are superimposed in the dashed rectangle; data for these dogs are indicated by white or black triangles (dogs 1 and 2, respectively).

Citation: American Journal of Veterinary Research 69, 10; 10.2460/ajvr.69.10.1262

Figure 2—
Figure 2—

Venous blood pH measured in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 5 field trials conducted at ambient temperatures of 2.2° to 29.4°C. The dotted line is the mean baseline value. Values measured at the 2 field trials conducted at ambient temperatures > 21°C (within oval outline) are significantly (P < 0.001) higher than values measured at trials conducted at ambient temperatures b 21°C. Values of pHv < 7.100 and > 7.600 are considered critical care alert values; dogs in which such values are detected require immediate attention or therapeutic intervention.c See Figure 1 for remainder of key.

Citation: American Journal of Veterinary Research 69, 10; 10.2460/ajvr.69.10.1262

Figure 3—
Figure 3—

Values of PvCO2 in Labrador Retrievers within 5 minutes of completion of a test (retrieval of birds over a variable distance on land [1,076 to 2,200 m]) at each of 5 field trials conducted at ambient temperatures of 2.2° to 29.4°C. The dotted line is the mean baseline value. Values measured at the 2 field trials conducted at ambient temperatures > 21°C (within oval outline) are significantly (P < 0.001) lower than values measured at trials conducted at ambient temperatures b 21°C. See Figure 1 for remainder of key.

Citation: American Journal of Veterinary Research 69, 10; 10.2460/ajvr.69.10.1262

Dogs with heat stress—During test 5, dogs 1 and 2 became incoordinated in all limbs and weak in their hind limbs and panted heavily. Both dogs were cooled with ice and were clinically normal within 15 minutes. The dogs had participated in several preceding tests without signs of heat stress. In a 12-month follow-up period during which the dogs continued to train and perform at field trials, no further problems with exercise or heat intolerance were detected. The data obtained from these 2 dogs during test 5 were recorded (Table 1) but not used in the analyses for the test. Because test 5 was the final test of the study and these 2 dogs were clinically normal during 12-month follow-up, data obtained from the dogs during the preceding tests were included in the analyses for those tests. In test 5, dogs 1 and 2 had higher rectal temperatures, higher pHv, and lower PvCO2 values than the other dogs completing that test. During the other tests in which dogs 1 and 2 were assessed, findings were not consistently different from the values in other dogs (Figures 1–3).

Discussion

Conclusions from 2 previous studies1,2 were that healthy Labrador Retrievers develop hyperthermia, respiratory alkalosis, hypocapnia, and mild metabolic acidosis (based on elevated blood lactate concentrations) during retrieving drills, training, and field trial competition. In 1 study, Matwichuk et al1 evaluated dogs that were performing a retrieving drill at ambient temperatures of 11° to 28°C; the drill involved retrieval of a dummy that was repeatedly thrown 37 to 46 m (40 to 50 yd) for 10 minutes. After exercise, dogs had significant increases in rectal temperature, arterial blood pH, and PaO2 and significant decreases in PaCO2 and blood bicarbonate concentration. There was no effect of ambient temperature on rectal temperature, but those researchers did not comment on the effect of ambient temperature on other variables. In the other study, dogs were monitored during training and field trials; after exercise, significant increases in rectal temperature and pHv and a decrease in PvCO2 were detected, compared with pre-exercise baseline values.2

On the basis of data collected from Labrador Retrievers competing in tests in colder weather in the present study, it became apparent that respiratory alkalosis and hypocapnia did not always develop. Instead, in ambient temperatures b 21°C, 14 of 22 (64%) dogs had mild acidosis, with pHv values less than the baseline value and PvCO2 values ≥ 20 mm Hg. Dogs that were exercised in temperatures > 21°C consistently developed an increase in pHv and a decrease in PvCO2, compared with pre-exercise baseline values. Exercise-associated changes in electrolyte concentrations and other venous blood variables at high and low temperatures were similar to those reported previously.1,2

Dogs respond to exercise by hyperventilating (ie, panting).5 Increased blood temperature is probably the most potent ventilatory stimulus during exercise because panting is a major mechanism for heat loss in dogs.6 It appears that at higher ambient temperatures, Labrador Retrievers in field trials are at risk for hyperventilating to such an extent that they develop severe primary hypocapnia and respiratory alkalosis; some of the dogs in the present study had a pHv value > 7.6 and PvCO2 value < 15 mm Hg.

Acute hypocapnia and respiratory alkalosis develop concurrently because hyperventilation causes a decrease in PCO2, an increase in pH, and an immediate compensatory decrease in bicarbonate concentration in the blood.7,8 Exercise and heatstroke are causes of respiratory alkalosis in dogs.6,7 With acute severe respiratory alkalosis (defined as pH > 7.60), humans develop light-headedness, confusion, paresthesia of the extremities, altered tendon reflexes, stupor, and generalized seizures.8 The mechanisms underlying these clinical signs include cerebral and myocardial hypoperfusion caused by arteriolar constriction, minor alterations in electrolyte balances such as decreased ionized calcium and potassium concentrations, and decreased release of oxygen to tissues as a result of a left shift in the oxyhemoglobin dissociation curve.7,9

In dogs, acute hypocapnia that is experimentally induced via mechanical hyperventilation results in reductions in cerebral and myocardial blood flow,10–12 although not all studies have confirmed coronary vasoconstriction.13 In anesthetized dogs, PaCO2 of approximately 20 mm Hg (which was probably within the range recorded in the dogs of the present study) reduced mean cerebral blood flow by 36%.11 Hypocapnia also affects spinal cord perfusion. A PaCO2 value of approximately 20 mm Hg reduced blood flow in the cervical and thoracic portions of the spinal cord of anesthetized dogs by > 80%.14 However, these results cannot be extrapolated directly to exercising dogs. A previous study1 in exercising clinically normal Labrador Retrievers revealed that PaCO2 values less than the values that caused impaired blood flow to the spinal cord and brain were not associated with apparent clinical effects.

In our present and previous2 studies of dogs undertaking field trials, exercise-associated changes in blood electrolyte concentrations were consistent with respiratory alkalosis (ie, decreased sodium, potassium, and ionized calcium concentrations and increased chloride concentration). Compared with baseline value, mean ionized calcium decreased approximately 6% in the present study. These electrolyte alterations were not considered clinically important because they did not reach a critical value (ie, a value outside the reference range, which warrants immediate therapeutic interventionc). However, a transient respiratory alkalosis with an associated decrease in blood ionized calcium concentration of approximately 5% was detected in clinically normal adult humans who hyperventilated while watching an exciting television program.15 The authors of that study postulated that the decrease in blood ionized calcium concentration was the cause of seizures under similar circumstances of watching television in children who were seizure-prone.15 Whether this mechanism could contribute to the occurrence of seizures in dogs with heat stress and EIC is speculative. Another mechanism underlying seizures concerns change in the pH of CSF as a result of respiratory alkalosis. In the opinion of some authors, respiratory alkalosis can cause CNS hyperexcitability and trigger seizure foci in predisposed dogs.16

Respiratory alkalosis and hyperthermia cause opposite shifts in the oxyhemoglobin dissociation curve. An increase in body temperature decreases the affinity of oxygen for hemoglobin (right shift of the oxyhemoglobin dissociation curve), thereby releasing more oxygen to tissues. In contrast, an increase in blood pH shifts the curve to the left, releasing less oxygen to tissues. With an increase in blood pH from 7.4 to 7.6 in conditions where oxygen tension is constant at 40 mm Hg, hemoglobin saturation increases from 78% to 83%.17 In the present study, there were 2 dogs in which pHv was > 7.6 when exercising on the 2 hottest days.

Exercise-induced collapse is a relatively recently recognized disorder of increasing importance in Labrador Retrievers, especially dogs used for hunting and field trials.18,19 Dogs affected with EIC develop incoordination and life-threatening collapse after 5 to 15 minutes of exercise and cannot participate in many types of strenuous activity. Signs first become apparent in young dogs, usually between 5 months and 3 years of age (mean age of onset, 14 months), coinciding with the age at which intense training commences.18 The disorder has clear pedigree associations.19

Although episodes of EIC occur at any environmental temperature, many trainers have observed that episodes are more likely to occur in warmer weather.g For example, one of the authors (JES) noted that the time to onset of collapse in 1 Labrador Retriever with EIC when retrieving in the same yard was 22 minutes at an ambient temperature of 8°C and 7.5 minutes at an ambient temperature of 22°C. Other investigators have expressed the opinion that the actual ambient temperature does not seem to be a critical factor contributing to collapse in dogs with EIC, but if the temperature is much warmer or the humidity is much higher than conditions to which the dog is accustomed, collapse may be more likely.18

In contrast to the respiratory alkalosis and hypocapnia in the Labrador Retrievers in the present study, Greyhounds develop a decrease in blood pH (arterial pH < 6.99) after racing.20 In Greyhounds that raced a distance of 402 m, the lowest mean PaCO2 was 19.3 mm Hg and mean arterial pH never exceeded 7.497.21 Heatstroke rarely affects racing Greyhounds, although their rectal temperature often is > 42°C after a 400-m race.22 However, racing Greyhounds run 400-m distances in < 30 seconds,20 compared with Labrador Retrievers that often run 5 to 10 minutes.

The results of the present study indicated that ambient temperature is another factor, in addition to the duration and intensity of exercise,1 in the physiologic responses to exercise in Labrador Retrievers. Originally, Labrador Retrievers were used to retrieve and swim in the cold climate around Newfoundland where the mean summer temperature is 14°C in coastal regions of the island. When running distances in the range of 1,000 to 2,000 m (distances that are frequently encountered at field trials), healthy Labrador Retrievers have a high rectal temperature, regardless of ambient temperature; when the ambient temperature is > 21°C, severe respiratory alkalosis and hypocapnia can develop.

Abbreviations

EIC

Exercise-induced collapse

pHv

Venous blood pH

a.

Eukanuba large-breed premium performance food, Iams Corp, Dayton, Ohio.

b.

Monoject 1-mL tuberculin syringes (with detachable 25 × 5/8inch needle), Sherwood Medical, St Louis, Mo.

c.

iStat portable blood analyzer, cartridges CG4+ and 6+, Heska Corp, Fort Collins, Colo.

d.

Nikon Laser 800 rangefinder, Nikon Corp, Melville, NY.

e.

Microsoft Office Excel 2003, Microsoft Corp, Redmond, Wash.

f.

Statistical Analysis System, release version 9.1.3, SAS Institute Inc, Cary, NC.

g.

Dr. Edward Aycock, past-president, National Retriever Club, Milwaukee, Wis: Personal communication, 2007.

References

  • 1.

    Matwichuk CL, Taylor S, Shmon CL, et al. Changes in rectal temperature and hematologic, biochemical, blood gas, and acid-base values in healthy Labrador Retrievers before and after strenuous exercise. Am J Vet Res 1999;60:8892.

    • Search Google Scholar
    • Export Citation
  • 2.

    Steiss JE, Ahmad AH, Cooper P, et al. Physiological responses in healthy Labrador Retrievers during field trial training and competition. J Vet Intern Med 2004;18:147151.

    • Search Google Scholar
    • Export Citation
  • 3.

    iStat portable analyzer quality control data. Available at: www.istat.com/products/docs/qc.pdf. Accessed May 20, 2008.

  • 4.

    Weather Underground Inc. Available at: www.wunderground.com/US/Region/US/Temperature.html. Accessed February 14, 2007.

  • 5.

    Musch TI, Friedman DB, Haidlet GC, et al. Arterial blood gases and acid-base status of dogs during graded dynamic exercise. J Appl Physiol 1986;61:19141919.

    • Search Google Scholar
    • Export Citation
  • 6.

    Wagner JA, Horvath SM, Dahms TE. Cardiovascular, respiratory, and metabolic adjustments to exercise in dogs. J Appl Physiol 1977;42:403407.

    • Search Google Scholar
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Contributor Notes

Supported by grants from the S. D. Bechtel Jr. Foundation, the R. K. Mellon Family Foundation, and Mr. W. E. Bowen.

The authors thank Chris Ledford, Wild Wind Kennels, Buckhead, Ga; Dr. Don Sorjonen, Professor Emeritus, Auburn University, Auburn, Ala; Mr. and Mrs. Joseph Cooper III, Atlanta Retriever Club, Waverly, Ala; and Paula Reissdorf, Ebony Gilbreath, and Judith Hones, Tuskegee University, Tuskegee, Ala, for technical assistance.

Address correspondence to Dr. Steiss.