provided in the two parallel long sides of the crate.4 Four days before
cold testing each dog was fitted with a wire face muzzle which served to
prevent chewing on equipment during testing. The dogs were also conditioned
to a crate similar to one used during testing.

Dogs were fed 4 ounces of P/d® dog food the morning of testing; dogs were
normally fed at 8:00 a.m. daily. Thirty minutes after feeding they were
weighed, prepared for the test, placed in a test crate identical to the cold
exposure crate, and transferred to the test chamber area.

In the room outside the environmental test chamber, baseline data were
obtained on the dogs for rectal temperature (Tre), heart rate (HR), respira-
tion rate (RR), and behavior (barking and excessive movement) for 45 minutes.
At the same time, air temperature and humidity were monitored for the test
crate inside the cold chamber to determine the crate's micro~environment with
dog absent. Starting at 10:00 a.m. regularly, dogs were hand-carried into the
environmental chamber and placed in the pre-chilled test crate. During cold
exposure the dogs continued to be monitored for the Tre, HR, and RR using
noninvasive methods (Figure 2).° Both barking and excessive movement were

Figure 2. Shows dog prepared for monitoring rectal temperature, heart rate,
and respiration rate. Dogs were able to move about freely inside test crate
during exposure to cold air temperature.

3


group were small; and two, there was considerable difference in the amount
of barking and excessive movement displayed by individual animals. Increased
activity during exposure to cold temperatures could be advantageous for
dogs, as metabolic heat would increase.

When the dogs were placed in the cold chamber exposure crate, the erate's
internal air temperature would increase (Table 7). For dogs exposes to near

TABLE 7. — Change in Air Temperature Inside Exposure Crate
(Baseline vs Testing)

Air Temperature Inside Crate
(°F)

Dog Baseline* Testing** Increase

Group (No Dog in Crate) (Dog in Crate)

A 31.4 38.4 7.0
B 31.7 36.2 4.5
c 19.9 25.4 5.5

*Average of 10 readings taken at 5 minute intervals.
*kAverage of 48 readings taken at 5 minute intervals.

32°F, this increase in internal crate temperature was shown to be greater
for the older (group A) dogs than for the younger (group B) dogs. It is
reasonable to expect that the older dogs contributed more heat input to
their crates! internal environment than did the younger dogs as evidenced
by their higher decrease in rectal temperature. In comparing the two young—
er (3-month-old) groups of dogs (B and C), results show the group C dogs
exposed to the subfreezing (20°F) temperature contributed more heat to
their environment than the warmer (32°F) exposed group B dogs; no doubt more
metabolic heat was being generated by the colder exposed group C dogs as
they showed more increased activity, faster heart rates, and less decrease
in respiration rates while maintaining their rectal temperatures above pre—
exposure values. The differences between pretest (no dog in crate) and cold
test (dog in crate) crate mean air temperatures were shown to be statistic-
ally significant (P<0.001) for groups A, B, and C.

DISCUSSION

When unacclimated dogs are exposed to cold air temperatures, events take
place to conserve body heat and prevent a drop in body temperature to dangerous.
levels. Dogs will make postural changes by lying down in a curled-up position.
The skin's cold receptors are stimulated causing the body hair or fur to
erect, which further provides effective insulation.® Cutaneous vasoconstric—

8


Average change in heart rate between baseline and the 4 hour cold ex-
posure values for groups A, B, and C are shown in Table 2. A significant

TABLE 2. - Heart Rate
(Baseline vs Cold Exposure)

Beats Per Minute (Average)
Dog Group Baseline* Cold Exposure** Increase
A 117 134 +17
B 153 181 +23
c 137 207 +70
*Average of 10 readings (5 minute intervals)
*kAverage of 48 readings (5 minute intervals)

increase in mean heart rate occurred during cold exposure for group A
(t= -3.10, P<0.05), B (t= -4.45, P<0.01), and C (t= -11.76, P<0.001). Only
one dog (from group A) had a cold exposure value lower than its baseline,
The increase in heart rate was not unexpected. Increased heart rates may be
related to the increased metabolic rate brought about by shivering and ac-
tivity.

Table 3 shows the average respiration rates for groups A, B, and C during
baseline and 4 hours of cold exposure. One dog from group A and three from

TABLE 3. - Respiration Rate
(Baseline vs Cold Exposure)

Dog Group Rate Per Minute (Average)
Baseline* Cold Exposure** Decrease
A 47 29 -18
B 57 47 -10
c 39 32 -7
* Average of 10 readings (5 minute intervals)
** Average of 48 readings (5 minute intervals)



monitored continuously, barking by means of an intercom while excessive
movement was observed visually through a window in the lighted chamber.
After 4 hours of continuous exposure to the cold environment the dogs were
removed from the chamber and returned to their living quarters where the
monitoring equipment was removed. After 30 minutes of observation they were
placed in their cages, given water, and observed for any evidence of sequela
for 7 days.

RESULTS

Although change occurred in several physiological parameters measured,
all dogs studied safely tolerated 4 hours of continous exposure to either
freezing or subfreezing air temperatures. No ill effects from the extreme
cold were observed during testing or during 7 subsequent days.

To simplify identifying the dogs in reporting results in the following
tables, the 6-month-old dogs exposed to near 32°F will be referred to as
group A, the 3-month-old dogs at near 32°F as group B, and the 3-month-old
dogs at near 20°F as group C.

Table 1 shows each group's mean rectal temperature before, and in response
to, cold exposure. Group A and B had mean decrease compared to an increase

TABLE 1. - Rectal Temperature of Beagle Dogs
During Cold Exposure

Dog Group* Mean Rectal Temperature (°F)
Start End Change 4 Hour Average
A 101.9 101.4 Decrease 0.5 101.7
B 101.3 101.0 Decrease 0.3 101.2
G 101.2 101.5 Increase 0.3 101.4
*10 dogs in each group.

for group C. Only one dog from group A finished 4 hours of exposure with a
rectal temperature higher than its starting value compared to three from
group B and six from group C. Three dogs each from group A and group B, and
seven dogs from group C, had a 4-hour mean rectal temperature higher than
their starting values. The paired t-test failed to show a statistically
significant difference between pretest rectal temperature values and results
after 4 hours of cold exposure for groups A, B, and C.

4


comparison between males' and females' rectal temperatures, heart rates, and
respiration rates during cold exposure. Although a notable difference in re-

TABLE 5. ~ Average Rectal Temperatures, Heart Rates, and
Respiration Rates for Groups B and C Dogs*
(Males vs Females)

Rectal Temperatures Heart Rate Respiration Rate
(°F) (BPM) (RPM)
Dogs B C B C B Cc
Males 101.3 101.4 179 206 48 31
Females 101.0 101.4 183 208 36 32
*Each group (B and C) has 5 males and 5 females.

spiration rate was shown between males and females of group B, statistically
there was no significant difference between males and females for rectal
temperatures, heart rates, or respiration rates in either group B or C,
The most observable difference between males and females during cold exposure
was in behavior. The increased barking and excessive movement demonstrated
by the male dogs was nearly twice that of the females for both groups B and
C (Table 6); however, these behavorial differences seen between the males

TABLE 6. ~ Behavior Comparision Between Group A and B
Males and Females During 4 Hours Cold Exposure*

Barking (Ave.) Excessive Movements (Ave.)

Periods (No.) | Time (Min.) [Periods (No.)| Time (Min. )
Dogs B Cc B Cc B Cc B Cc
Males 11.8 16.0 29.6 36.1) 10.6 15.4 23.3 25.7
Females 564 8.8 10.8 8.6 7.4 8.8 14.3 10.2

*Each group (B and C) had 5 males and 5 females. There were a
total of 48 (5 minute) periods during cold exposure.

and females were found not to be statistically significant for either
group B or C. Two factors may have contributed to no significant
differences being found: One, the numbers of males and females in each


ACKNOWLEDGMENTS

The authors gratefully acknowledge the efforts of Dr. Earl D. Folk and Mark
H. George, Biostatistical Section, Civil Aeromedical Institute, for preparing
the statistical data.



the crates' micro-environment would be increased and maintained over the
outside-of-the crate air temperature. The crate would need to be located in
areas where air flow (wind) was at a low velocity. If the crate were posi-
tioned such that an increased air flow were passing through the crate open-
ings, then the wind chill factor would adversely affect the dogs. The fact
that the same size crate was used for both the 6-month-old and 3-month-old
dogs may account for some of the in-crate temperature increase of the older
dogs. Typically, however, the same sized crate is often used to transport
dogs of different sizes. It is also expected that the larger dogs would
contribute more heat to the crate environment, since they do have more body
mass exposed to the environment. McIntyre et alll reported that cold
exposure metabolic heat production in the young dog is very similar to that
of the adult. Thus, it is unlikely there was a significant difference in
metabolic heat production between the two age groups. Once the dogs were
removed from the cold environments, shivering stopped almost immediately,
and from all appearances they were essentially the same as prior to cold
exposure.

SUMMARY

We found that healthy beagle dogs (3 and 6 months of age), confined in a
crate having a 14-percent ventilation area, can safely tolerate 4 hours of
continuous exposure to freezing and subfreezing temperatures. None of the
animals in our study showed any post-exposure sequela during the 7-day
observation period, All dogs maintained a rectal temperature in the expected
normal range. Heart rates usually increased during cold exposure, while
respiration rates decreased for most dogs. Barking and excessive movement
increased, but this is partly anticipated when dogs are introduced into
unusually cold environments and isolated from human contact. However, these
activities subsided as the dogs became more familiar with the new cold

environment.

Three-month-old male and female beagle dogs exposed to cold temperatures
showed few differences in rectal temperature, heart rate, and respiration
rate. However, the 3-month-old males did display more barking and activity
than did their female counterparts.

Placing a dog inside a pre-chilled transport crate caused a rise in in-
crate ambient air temperature. This in-crate temperature increase was
maintained throughout the exposure period, during which time the outside-
crate air temperature was held fixed. This response was indicative of the
satisfactory compensatory heat production experienced by the dogs. As far as
the dogs were concerned, they were experiencing the effects of the created
warmer temperatures, rather than colder chamber temperatures.

10


«

tion occurs, reducing heat loss between the skin and the environment.’ As
vasoconstriction develops, the surface temperature of the back, tail, and
foot pads will lower and heart rate will increase.8 In our studies, only 1
out of 30 dogs had a 4-hour average heart rate lower than its baseline value.

Shivering is a very important response to cold exposure and a major
contributor to body heat production. All our dogs experienced shivering, but
we were unable to determine exactly when it began, because the dogs were
moving about the crate during the early stages of exposure. Shivering
increases oxygen consumption, muscular activity, and metabolic rate.9 Dogs
have been reported to show a 3-to-4-fold increase in metabolism when
shivering, 10 Jensen and Ederstrom report that as a dog matures, shivering
becomes increasingly more powerful and sustained.8 An animal exposed to the
cold will not necessarily experience a lowering of body temperature as
shivering occurs.2 Large dogs are reported to cool more slowly than smaller
dogs because they have less surface area per unit of, body mass.

When dogs are exposed to cold temperatures, respiration rates are report—
ed to increase, ! However, at the temperatures to which our dogs were exposed,
average 4-hour respiration rates for 23 of 30 dogs were decreased from base-
line values.

Two factors may have contributed to the lower respiration rates seen
during cold exposures. First, baseline respiration rates were on the high
side of normal to begin with, as many dogs were quite anxious during the time
period before baseline data was monitored. Secondly, it is reasonable to
suspect that because the dogs were being exposed to such cold temperatures
for the first time, their body efforts were being concentrated on conserving
body heat through shivering and that respirations became deeper and less
frequent.

The dogs in our study were able to maintain rectal temperatures very
close to their baseline values during 4 hours of cold exposure. The two 3-
month-old groups (B and C€) were possibly a little more successful than the
6-month-old dogs because of their increased activity. In addition, the
group C dogs showed a considerable increase in heart rate during cold ex-
posure. During short periods of increased activity, rectal temperatures
would rise as much as 0.5°F, but as activity subsided, rectal temperatures
would lower to pre-activity levels. If the dogs had lain quietly without
any activity, one would have expected rectal temperatures to have been some-
what lower than shown. Moderate periodic increases in activity during cold
exposure would appear beneficial in assisting dogs in maintaining a level
body temperature, whereas increased activity in a hot environment would be
disadvantageous to dogs. In either situation, increased activity to the
point of exhaustion would be detrimental. Data providing a baseline act-
ivity level during 4 hours of confinement while in a more nominal temper-
ature (e.g. 70°F) are not available for comparision.

a ae study indicates that in cold weather, if dogs were housed in a
vee erate having 14 percent or less ventilated area, the temperature of

9


groups B and C, experienced an increase in respiration rate; however, the
average respiration rate for each group decreased during cold exposure. The
change in mean respiration rate values between baseline and cold exposure
was statistically significant for only groups A (t=3.87, P<0.001) and C (t=
2.53, P<0.05). Were it not for variations in group B dogs' baseline respir-
ation rates, they may also have shown a significant decrease. Although a
decrease in respiration rate was shown (baseline versus cold exposure), this
decrease is not critical for the dogs, since all were within acceptable
limits for anxious dogs.

Prior to entering the cold chamber, the dogs were generally quiet and
calm with only minimal barking and excessive movement; however, when intro-
duced into the cold chamber, many dogs would begin barking and displaying
excessive movements, such as pawing at the crate walls, crawling around on
the crate floor, and rolling. Behavorial activity was monitored during
testing and recorded at 5 minute increments. This behavorial activity, shown
in Table 4, compares the average number of 5-minute increment periods and
time (in minutes) spent by dogs in each group that displayed this behavior.

TABLE 4. - Comparison of Behaviorial Activity Between
Groups A, B, and C Dogs During Cold Exposure
Barking (Average) Excessive Movements (Average)
Dog Group} Dogs |Periods* Time Dogs Periods*| Time
(No.) | (No.) Qftin.)| (No.) (No.) | (fin.)
A 5 7.6 9.4 7 3.0 3.1
B 9 9.5 25.3 10 9.0 18.8
Cc 10 12.4 22.4 9 13.4 20.1
*There were a total of 48 (5 Min.) Periods during cold exposure.

Dogs in the younger groups (B and C) spent more time barking and displayed
excessive movement more often than the older group A dogs. While in the
cold chamber, 5 dogs from group A never barked and 3 dogs displayed no exces-
sive movement. Group C dogs, exposed to the coldest temperatures, displayed
parking and excessive movement during about one-fourth of the total number
of 5 minute periods.

Because both males and females were used in groups B and C, we wanted to
determine if any of the responses may be sex related. Table 5 shows a

6


respectively) 10 3-month old dogs were used (5 females and 5 males each,
weighing between 8 and 12 pounds). All dogs came from the same purebred
colony of research animals, many of which were litter mates. They were
maintained on a diet of Purina Puppy Chow and/or Hill's P/d® canned dog
food, depending on their arrival weight.

Testing order was determined by body weight, with the heavier dogs
tested first. None of the animals received any form of medication for at
least 7 days prior to the experiments. The dogs were tested individually
in a simulated shipping crate (30"L X 18"W X 22"H) constructed of clear
plastic material; this permitted observation of the dogs at all times
(Figure 1). The ventilatory openings, prescribed by regulations, were

- ae a”. Saar
_@?

e
=
ee

ed

Sees

Figure l. Simulated shipping crate used for exposing beagle dogs to
cold environments (30"L X 18"W X 22"H). Each of the two parallel long
sides provides 16 percent openness. The two parallel short ends are
not open for ventilation. Total openaess of the crate (considering all
four sides) equals 14 percent ventilation.


TOLERANCE BY UNACCLIMATED BEAGLE DOGS TO
FREEZING AND SUBFREEZING TEMPERATURES

INTRODUCTION

Current transportation standards for shipping dogs by commercial means,
such as by commercial air carrier aircraft, state that the ambient air temper-
ature surrounding a dog shall not be allowed to fall below 45°F; however,
there is an exception: Dogs will be permitted to be transported or shipped
from one point to another if accompanied by a certificate issued’ by an ac-
credited licensed veterinarian, certifing that the animals in question are
acclimated to air temperatures below 45°F.! In 1978, the United States
Department of Agriculture (USDA) considered lowering the minimum air temper-
ature limits for transporting dogs from 45°F to 35°F. Much controversy
developed between humane groups, dog owners, handlers, and shippers. At
that time, sufficent scientific evidence was not introduced to show that
dogs would not be harmed by colder temperatures during the transport period;
thus, the standards remained unchanged. Many dogs throughout the United
States live out-of-doors during cold winter months and remain healthy at
temperatures well below 45°F. Dogs are also raised indoors during the
winter and are exposed to the out-of-door elements for only short periods.
These indoor raised-animals are the primary subject of concern. Long haired,
well insulated dogs, such as the Husky, tolerate extremely cold weather with
no harm to body physiology.2 Of greater concern were the effects of such
exposure on the short-haired, less well insulated dogs, such as the beagle.
Spealman> reported some dogs were able to maintain a normal body temperature
for five hours when immersed up to the level of the neck in 32°F water.
Durrer and Hannon2 subjected indoor-housed beagles to out~of-door temper-
atures between ~4 to +14°F for 5 hours daily, and later 12 hours daily. The
only undesirable responses reported were some evidence of mild frostbite on
the feet from the snow and violent shivering on initial exposures. Gradually
the intensity of shivering decreased and the cold injuries were transient.

In the cargo compartment of commercial air carrier aircraft, where dogs
would be stowed during transport, the ambient air temperature has been reported
to be as low as 32°F with ice forming in the compartment.

In an effort to better define the effects of freezing and subfreezing air
temperatures on short haired dogs, the FAA, under a cooperative interagency
agreement with the USDA, offered to investigate cold temperature responses
on unacclimated beagle dogs.

METHODS AND MATERIALS

Thirty healthy unacclimated beagle dogs were used in three cold temper-
ature experiments, using 10 dogs per experimental condition. The cold temper-
ature environment was provided by an environmental chamber (10'H X 10'L X
8'W) at the Civil Aeromedical Institute. The first test environment (32°F)
was studied with 10 male dogs, 6 months of age, weighing between 19 and 22
pounds. In each of the second and third experiments (at 32°F and 20°F,

1


Technical Report Documentation Page

T. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/AM- 87/3

‘4. Title ond Subtitle . : 5. Report Date
Tolerance by Unacclimated Beagle Dogs to Freezing
March 1987

and Subfreezing Temperatures
6. Performing Organization Code

8. Performing Organization Report No.

7. Author! s)

Gerald D. Hanneman and James L. Sershon

9, Performing Organization Name and Address 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute

P. O. Box 25082 1. Contract or Grant No.

Oklahoma City, OK 73125

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address
Office of Aviation Medicine

Federal Aviation Administration
800 Independence Avenue, SW.
Washington, DC 20591

14. Sponsoring Agency Code

1S. Supplementary Notes This work was performed under task AM-E-83-VM-1. Partial funding
was provided by the United States Department of Agriculture under an FAA/USDA inter-
agency cooperative agreement.

16. Abstract

Beagle dogs (3 and 6 months of age) unacclimated to cold air temperatures were
exposed to temperatures near freezing (32 “F) or subfreezing (near 20 F),

while housed in simulated transport crates. All exposed dogs safely tolerated 4
hours of continuous cold exposure as evidenced by maintenance of rectal temperatures
within an acceptable normal range. Heart rate, respiration rate, and behavior
(barking and excessive movement) showed no deleterious change during exposure.

No significant differences between males and females were found for rectal tempera-
ture, heart rate, and respiration rate. However, the males displayed more barking
and excessive movement than females of the same age. The micro environment air
temperature in the simulated transport crate was increased significantly (P. 0.001)
by the presence of a dog during exposure to freezing temperatures. Results
indicate that no harmful stress was encountered by the dogs exposed to 32 F and

20 °F for 4 hours.

17. Key Words 18, Distribution Statement
Animals, dogs, animal physiology, Document is available to the public
environmental stress, cold stress. through the National Technical Information

Service, Springfield, Virginia 22161.

19. Security Classif, (of this report) 2. Security Classif, (of this page) Bi. No. of Pages | 22, Price

Unclassified Unclassified 15

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized


2.

3.

10.

ll.

REFERENCES

Code of Federal Regulations, Revision of Standards for the Transporta-
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Certain Other Warmblooded Animals. CFR Admendment 78-75, Title 9, Chap-
ter 1, Subchapter A, Part 3, December 1, 1978.

Durrer JL, Hannon, JP. Seasonal Variations in Caloric Intake of Dogs
Living in an Artic Environment. Am J Physiol 1962; 202 (2): 375-78,

Spealman CR. Body Cooling of Rats, Rabbits, and Dogs Following Immer-
sion in Water, with a Few Observations on Man. Am J Physiol 1946,
146: 262-6.

Federal Register, Ventilation Requirements of the Transportation Stand-
ards for Dogs and Cats. ACFR part 3.12, Animal Welfare; Standards for
the Humane Handling, Care, Treatment, and Transportation of Dogs and
Cats, FR Vol. 45, no. 108, June 3, 1980.

Hanneman GD, Sershon, JL. Tolerance Endpoint for Evaluating the Ef-
fect of Heat Stress in Dogs. Washington D.C.: Department of Trans—
portation/Federal Aviation Administration Report No. DOT/FAA/AM-84/5,
1984,

Bard P. Body Temperature Regulation. In: Bard P, ed. Medical Physiol-
ogy, llth ed. St. Louis: The CV Mosley Company, 1961: 526-58.

Andersson BE. Temperature Regulations and Environmental Physiology, In:
Swenson MJ, ed. Duke's Physiology of Domestic Animals. 9th ed. Ithaca
and London: Comestock Publishing Associates, a division of Cornell
University Press, 1977: 686-95.

Jensen C, Ederstrom HE. Development of Temperature Regulations in the
Dog. Am J Physiol 1955, 183: 340-4.

Hammel HT, Hardy JD. Shivering only Variable Source of Heat in Intact
Unacclimatized Dogs Upon Exposure to Cold. Fed Proc 1957; 16: 54.

Folk GE Jr. Introduction to Environmental Physiology. Philadelphia: Lea
and Febiger, 1966: 98-136.

McIntyre DG, Ederstrom HE. Metabolic Factors in the Development of
Homeothermy in Dogs. Am J Physiol 1958, 194 (2): 293-6.

ll

U.S. GOVERNMENT PRINTING OFFICE: 1987-722-151 Region 4.