Table 7. Percent of Total Barking and Excessive Movement That
Occurred During the First Hour of the Total 6 Hours of
Heat Exposure*

First Hour Occurrences

i Environment Barking Excessive Movement
|Temperature/Humidity Percent of | Percent of Percent of Percent of
(°F/ZRH) Total Periods | Total Minutes | Total Periods Total Minutes
i
1
85/90 63 ' 67 | 52 63 |
| 1
' \
90/70 55 | 60 | 49 54
t 1
| | i
95/50 43 72 | 42 53
100/30 46 53 64 76
|

*Refer to Tables 5 and 6 for total periods and minutes of barking and
excessive movement.

12


Figure 1.

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


intensely within the first hour in the test environment. Initial
isolation in this strange environment may have contributed
slightly to early barking. Usually within an hour, the dogs
would then generally calm down and appear to accept the situation
with only sporadic episodes of activity. Rectal temperature
woulda generally rise when barking or excessive movement occurred.
However, when the dogs became quiet, rectal temperature would
decline unless activity had been quite intense.

Open-mouth panting with the tongue extended was normal
during heat exposure. However, two dogs at 85 °F/90%RH and one
dog at 90 °F/70%RH never exhibited open-mouth panting during 6
hours of heat exposure. The peak rectal temperatures for these
three dogs were 101.4, 101.6, and 102.3 °F respectively. The
time when panting began appeared to be influenced by an increase
in either air temperature or humidity, all other conditions
remaining constant. Rectal temperatures when panting started
were very similar among the groups, regardless of the
environment.

General observations of the test animals seemed to indicate
that the first 30 to 60 minutes of exposure to hot environments
are critical for a dog in establishing the ability to success-
fully tolerate the heat. Early open-mouth panting with little or
no excitement appears to enable the dogs to maintain a lower
rectal temperature for a longer period.

Conclusions

Based on separate studies at CAMI, a hot/humid environment
which causes a dog's rectal temperature to rise above 108 °F
exposes that animal to possible heat stroke and even death. Such
environments should not be considered safe for shipping dogs.

Healthy adult dogs transported in USDA-approved shipping
kennels having no less than 14 percent overall ventilation
capacity should be expected to safely tolerate air temperatures
of 100 °F or less during 6 hours of transport, provided proper
consideration is given to the humidity of the shipping
environment.

Our studies also indicated that any given dog's behavior
cannot be reliably predicted when that dog is confined to a
shipping kennel and exposed to a stressful hot/humid environment.
When a fractious dog is anticipated, assistance in helping that
dog maintain a relative state of quiescence is advantageous.

This can usually be accomplished by administering a low level
tranquilizer.

The temperature/humidity index discussed in this report

should serve as a useful guide for shippers and airlines when
transporting dogs during the summer months.

16


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ill effects from the exposure. None of the exposed dogs were
allowed to succumb to any of the nine hot/humid environments
studied.

Table 2 shows the average time in minutes at which dogs
exposed to each environment started open=-mouth panting and at
what rectal temperature the open-mouth panting began. Data
indicate that, when the air temperature remained constant, the
dogs exposed to the higher humidity start the panting process
earlier than those at lower humidities, If humidity remained
constant, the dogs exposed to the higher air temperatures also
started panting earlier than those at lower temperatures.
However, there was little difference in each group's rectal
temperature when open-mouth panting started.

The ability of the dogs to safely tolerate hot environments
was dependent on the air humidity (Table 3), as well as air
temperature. Data suggests that, for dogs to maintain approx-
imately the same effective rate of evaporative cooling, relative
humidity needed to be lowered by 20 percent (e.g., 90 to 70

percent RH) for every 5 °F increase in air temperature above
85 OF,

Only four temperature/humidity conditions were safely
tolerated by all exposed dogs for 6 hours. Data from these four
conditions is presented in greater detail in Tables 4, 5, 6, and
7. Each group's average rectal temperatures increased as the
environment's air temperature increased. However, all dogs were
able to maintain a rectal temperature less than 108 °F throughout
exposure because relative humidity was sufficiently lowered as
air temperature increased (Table 4). Figure 2 shows the pattern
of average rectal temperature for each test condition during 6
hours of exposure. The average rectal temperature at the end of
6 hours for dogs exposed at 85 °F/90 percent RH was lower than
the starting value.

Dogs tested in each environment displayed discontent from
the test conditions by barking and exhibiting excessive movement
(movement other than the expected repositioning of the body
during a 6~hour period). However, not all dogs, at each test
condition, displayed barking or excessive movement. Those that
did bark all started during the first hour of exposure, whereas
only some of the dogs that displayed excessive movement initiated
this activity during the first hour of testing. Table 5 shows
that the average time spent barking increased as the air temper-
ature of the test environment increased. However, there was no
clear relationship between excessive movement and the test
environment temperature (Table 6). More than 50 percent of all
barking and excessive movement took place during the first hour
of testing (Table 7).


Table 1. Percentage of Dogs Safely Tolerating 6 Hours of Continuous
Exposure to Hot Air Temperature/Humidity Conditions
While Confined in a Crate Having 14 Percent of Its Wall
Surface Open for Ventilation.

Temperature/Humidity Environment Tolerance*
°F /2RH 4
85/90 100
90/70 100
95/50 100
95/70 70
95/90 20

100/30 100
100/50 80
100/70 0
105/50 10

*Ten dogs per environmental condition


REFERENCES

Bard P. Body Temperature Regulation. In: Bard P, ed.
Medical Physiology, lith ed. St. Louis: The CV Mosley
Company, 1961:526-55,.

Code of Federal Regulations (CFR), Revision of Standards for
the Transportation and the Handling, Care, and Treatment in

Connection therewith of Dogs, Cats, Rabbits, Hamsters
Guinea Pigs, Non-Human Primates, and Certain Other Warm
Blooded Animals. CFR Amendment 78-75, Title 9, Chapter 1,
Subchapter A, Part 3, December 1, 1978,

Federal Register, Ventilation Requirements of the Transpor-
tation Standards for Dogs and Cats, 9 CFR, Part 3.12,

Vol. 45, No. 108, June 3, 1980.

Hanneman GD, Sershon JL. Tolerance Endpoint for Evaluating
the Effects of Heat Stress in Dogs. Washington, D.C.:
Department of Transportation, Federal Aviation Administra-
tion, Office of Aviation Medicine Report No. DOT/FAA/AM-
84/5, 1984,

Ingram DL, Mount LE, Man and@ Animals in Hot Environments.
New York, Heidelberg, Berlin: Springer-Verlag, 1975.

17


Table 3.

Effects of Relative Humidity on Animal Tolerance

When Air Temperature and Ventilation Remain Constant

Environmental Condition

Crate Openness Air Temperature RH Animal Tolerance*

% °F % ’
50 100
95 — 70 70
oS 90 20

14
. 30 100

a
TM100 50 80
—

oS 70 0

*Ten dogs were exposed to each environment.

Tolerance meant a dog

could remain in the environment for 6 hours and maintain a rectal

temperature less than 108 °F at all times.



ACKNOWLEDGMENTS

The authors gratefully acknowledge the assistance of Dr.
Earl D. Folk, Biostatistical Section, Civil Aeromedical
Institute, for preparing the temperature/humidity
tolerance index, and to Dr. R. B. Deal, Jr., Department
of Biostatistics and Epidemiology, University of
Oklahoma Sciences Center, Oklahoma City, Oklahoma, for
formulating the mathematical equation used in
determining the temperature/humidity tolerance index.


Table 6. Average Number of Periods and Minutes in Which Excessive
Movement Occurred During 6 Hours of Heat Exposure
rene
Environment Dogs Displaying | Periods During Which Time of Actual
\Temperature/Humidity | Excessive Movement Excessive Movement Excessive Movement
\ Occurred *
(°F /%RH) (Number) (Number) (Minutes)
85/90 8 7.3 12.3
90/70 7 6.5 7.8
95/50 9 11.0 12.5
100/30 6 7.2 10.2
| _|

Ten dogs were tested at each environment, but average values are
expressed per actual number of active dogs in each category.

*Each hour consists of 12 equal 5-minute periods.

10


Table 5.

Average Number of Periods and Minutes in Which Barking

Occurred During 6 Hours of Heat Exposure

Environment Dogs Barking Periods During Which | Time of Actual
Temperature/Humidity During Exposure Barking Occurred * Barking
(°F/ZRH) (Number) (Number) (Minutes)
85/90 8 6.5 9.7
90/70 10 10.4 11.6
95/50 9 16.7 12.7
100/30 7 18.2 29.1

Ten dogs were tested at each environment, but average values are
expressed per actual number of active dogs in each category.

*Each hour consists of ,12 equal 5-minute periods.



Table 2. Relationship of Temperature or Humidity Change
to Time When Open-Mouth Panting Begins

Temperature/Humidity Average Time When Average Rectal Temperature
Panting Began When Panting Began
(°F/%RH) (Minutes) (°F)
100/30 9.6 102.5
100/50 8.8 102.2
100/70 8.3 102.6
95/50 13.1 102.7
95/70 10.5 102.4
95/90 7.7 102.4
95/50 13.1 102.7
100/50 8.8 102.2
105/50 6.4 102.4
90/70 10.5 102.4
95/70 9.6 102.5
100/70 8.3 102.6



diet of Purina Puppy chow ® and/or Hill's pp® canned food,
depending on their arrival weight. None of the animals received
any medication for at least 7 days prior to testing. Their order
for testing was determined by body weight, with the heavier dogs
tested first. Prior to testing, all dogs were semiconditioned to
a wire face muzzle (used during testing to prevent chewing of the
test equipment) and a test shipping crate.

Oy the days of testing, the dogs were fed 4 ounces of
i11's® PD canned food. Thirty minutes later they were weighed
and prepared for testing. A flexible thermistor probe was
inserted about 6 inches past the anal sphincter to monitor rectal
temperature (RT). Both RT and behavior (barking and excessive
movement) were monitored continuously for all dogs. At 9:00 a.m.
daily the dogs were transported in a test crate to a room
outside the test chamber, where baseline data were obtained for
45 minutes; ambient air temperature was 74-75 °F. All dogs were
tested individually only once in a crate with 14 percent
openness to satisfy required ventilation (3) (Figure 1). At
10:00 a.m. the dogs (one test per day) were handcarried into the
exposure chamber and placed in a preheated test crate. Nine
temperature/humidity conditions were studied using 10 dogs in
each condition. The test environments were provided in the Civil
Aeromedical Institute (CAMI) animal environmental chamber (10'H
by 10'L by 8'W). Airflow supplying the heat and humidity to the
chamber was located in the ceiling and not directed at the open
areas of the crate. Environmental conditions desired were
obtained 12 hours in advance of testing and maintained throughout
heat exposure. Excessive movement was observed through a window
in the chamber. Barking could be heard through an intercom
system. Chamber and crate temperature/humidity were recorded
every 5 minutes,

It had been demonstrated previously that healthy dogs could
tolerate a hot environment without residual effects as long as
their rectal temperatures remained below 108 °F (4). If a dog's
rectal temperature reached 108 °F during the testing, he was
removed from the test. If a rectal temperature of 108 °F was not
reached, the dogs were monitored during a maximum of 6 hours of
exposure. Following testing, dogs were returned to their living
quarters and observed for a minimum of 7 days for any signs of
postexposure sequelae.

Results

Table 1 shows the percentage of dogs which safely tolerated
6 hours of continuous exposure to each environmental condition
while confined in a crate with 14 percent of its wall surface
area open for ventilation. In this study, the use of the phrase
"safely tolerate" refers to the natural ability of the dogs to
maintain a rectal temperature less than 108 °F at all times
during exposure to a hot/humid environment and not demonstrate

2


Results from all nine environments studied provided the data
necessary to formulate equations that would show which hot
weather temperature/humidity combinations could or could not be
safely tolerated by 100 percent of the dogs exposed.

Fitting of Tolerance Data

i Assiduous inspection of the data indicated that a linear
equation (of the form 4T + H + constant) described the line of
separation between 100 percent tolerance and less than 100
percent tolerance. T = the air temperature ( F) of the exposure
environment, H = the relative humidity ($RH) of the environment,
and the constant = 430. A parallel line also appeared in the
area of zero tolerance. A difference of 60 existed in the 4T + H
between 100 percent tolerance and zero tolerance. If we let X =
4T + H - 430, then when X = 0, we have 100 percent tolerance, and
at X = 60, we have zero tolerance. The trivial mathematical
solution shows that there is 100 percent tolerance for X less
than zero, and zero tolerance for X greater than 60. Assuming an
"S shaped" response over the interval between X = 0 and xX = 60, a
cubic equation, which has been used frequently to fit biological
response, was used to fit the range.

A general form of the cubic equation is:
ax3 + bx2 + cx +d =1 {Eq.1]
If we let x=0, then d=1. We want the cubic to be zero at x=60.
i.e.: a603 + b602 + c604+1=0 [Eq. 2]
Additional properties needed are for derivatives to be equal to
zero when x=0 and when x=60. The derivative of equation (1) is:

3ax2 + 2bx + c = 0

when x = 0, then c = 0
when x = 60, 3a602 + 2b60 = 0
* which leads to b = -90a.

Substituting into equation (2), we solve for a = 1/108,000.
Substituting into the general cubic equation we have:

1/108,000 x3 ~ --ps29.--- * 4241 = tolerance
’
2 —.
and 1 - Saas Fie * 100 = percent tolerance [Eq.3]

13


(°F)

TEMPERATURE

Table 8. High Temperature/Humidity Index for
Shipping Healthy Adult Beagle Dogs

RELATIVE HUMIDITY (%)

1 14 12 22 26 30 34 58 42 de 50 54 58 62 66 70 7 7H RD G6 BO 24 98
100 100 100 100 100 100 100 200 100 180 190 10 196 18a Loe 100 100 tu 108 190 190 190 208
100 100 100 100 100 190 168 100 100 100 160 100 108 160 160 100 10 100 £00 400 L890 jo9 4e0
100 100 100 108 200 200 100 L00 109 100 106 199 100 ioe 100 109 100 ino 190 160 100 102 90
100 10g.100 200 1g0 490 100 19p 400 149 109.109 100 100 160 100 100 169 106 100
100 1@io : EE Aloo 100 i0OMo MOMs oP Mice 190 100 100 190 100 99
100 4 0 Mei 10gf00 100 1ygago Ngo] NG BBmioo 100 100 100 190 08 55
100 100 100 100 100 100 100 100 100 100 100 190 100 190 100 100 100 190 100 9 98 9G
190 160 100 100 100 100 100 100 100 100 100 100 400 160 100 100 100 100 196-89 95 9h G3
100 100 100 100 199 100 100 100 100 100 109 199 209 298 100 200 190 19 95 9) 83 7
100 200 100 102 100 100 200 100 100 100 190 95 90 83 J 65
100 100 100 100 100 100 100 100 190 190 190 13 j 5 90 83 4 65 55
100 100 100 100 100 190 100 100 100 100 100 9 95 90 83 74 65 5S at
100 100 100 100 ioe 100 100 100 100 190 i20 9 90 83 76 65 85 4
100 180 100 100 160 160 149 100 160 100 106 30 83 74 BF 55 5 35 Ze
100 100 100 100 190 100 400 100 ine i900 t0¢ 83 74 65 55 45 35 26 iB
100 100 100 100 100 100 100 166 190 180 19p 74 6B 55 a5 38 2% 8 to
100 100 100 100 100 100 100 100 100 ¢ 6 55 6 HH % 1 WF
100 100 100 100 190 100 108 108 9% 45 38% 18 1b 5 I
100 100 100 200 100 100 100 199-69 95 99 93 35% 8 19 5 1 6
100 100 100 100 106 90 83 74 of Hote 18 18 5 toe 8
100 100 100 t00 100 1 “5 55 % 1 i § 1 a 8 8
100 100 190 100 19 599 8} 74 68 55 45 1 5 1 00 5 0
100 100 100 100 99 95090 83. 74 65 55 10 1 0
L0G 100 100 99 35 oo 7 IN: 5 7 N E a
100 100 99 95 tg 3 i a t
100 99 95 90 83 74 65 55 4 35% 18 bf 1 og DO UD 8 Ue

The calculated safety zone shows the temperature/humidity combinations
healthy adult dogs could safely tolerate for 6 hours of continuous
exposure when confined in a shipping crate with no less than 14 percent

of its total wall surface open for ventilation. Temperature/humidity
combinations beyond 100 °F/30% RH and 85 °F/90% RH were not tested on dogs.
The calculated danger zone indicates the chances of a dog safely
tolerating those temperature/humidity combinations when tolerance is

less than 100 percent.

15


A TEMPERATURE/HUMIDITY TOLERANCE INDEX FOR
TRANSPORTING BEAGLE DOGS IN HOT WEATHER

Introduction

Pet owners, humane organizations, shippers, and others have
long been justifiably concerned about the health and safety of
dogs when transported by commercial aircraft during hot weather.
Because animal deaths have occurred in air transportation during
hot weather seasons, the United States Department of Agriculture
(USDA) incorporated air temperature limits in the Animal Welfare
Act, which applies to dogs shipped by commercial conveyances.

Present transportation regulations stipulate that dogs shail
not be transported when the ambient air temperature surrounding a
live dog exceeds 85 °F or if the animal will be subjected to an
air temperature in excess of 75 °F for more than 4 hours at any
time (2). While this regulation affords some assurance for safe
and humane treatment during transport, it also presents the
problem for the shipper and the airline that since temperatures
above 85 °F are not uncommon in the summer, the consignee of a
dog cannot be certain whether their animal will be accepted for
shipment by the airlines because of different interpretations of
the regulations.

Dogs can often withstand extremely warm air temperatures,
if airflow is adequate and not restricted; water is available for
drinking; and the humidity of the environment remains low. A
dog's primary and most efficient mechanism for dissipating excess
body heat is by evaporative heat loss through open-mouth panting.
High humidity restricts evaporative heat loss and inhibits
effective cooling in the dog. Present standards do not address
humidity in determining warm air temperature limits.

The purpose of this study was to determine which warm air
temperature/humidity combinations would be safely tolerated by
short-haired dogs confined in a shipping crate of 14 percent
ventilation and to use this data to develop a temperature/humidi-
ty tolerance index for dogs subjected to shipping containers (14
percent ventilation) during air travel in hot weather months.

Methods

Dogs selected for the study had to be of the same sex and
uniform in age, size, weight, body conformation, breed, and
evenness of temperament. Breeding background had to be
verifiable, and the dogs had to be readily available. The dog
type that fit these criteria was the colony-bred beagle. Dogs
used in experiments were healthy males between 6 and 7 months of
age and weighed from 18 to 23 pounds. They were maintained on a

1


Technical Report Documentation Page

T.” Report No. 2. Government Accession No.

DOT/FAA-AM-87

3. Recipient's Catalog No.

4, Title and Subtitle 5. Report Date

A TEMPERATURE/HUMIDITY TOLERANCE INDEX FOR November 1987
TRANSPORTING BEAGLE DOGS IN HOT WEATHER 6. Performing Organization Code
AAM-114
[8. Performing Organization Report No.
7. Author! s)
Gerald D. Hanneman and James L. Sershon
9. Performing Organization Nome and Address 10. Work Unit No. (TRAIS)
FAA Civil Aeromedical Institute
P.O. Box 25082 11. Contract or Grant No.

Oklahoma City, Oklahoma 73125

13. Type of Report and Period Covered

12. Sponsoring Agency Name ond Address.
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue. SW. 14 Sponsoring Agency Code
Washington, D.C. 20591

OAM report

15. Supplementary Notes

This work was performed under tasks AM-E-80-VM-1, AM-B-81-VM-1 and
AM-B-82-VM-1.

16. Abstract

Male beagle dogs were subjected to various hot air temperature/humidity
cambinations in an attempt to develop a safe temperature/humidity index for dogs
being transported by aircraft. Only those environments in which all exposed
dogs could maintain a rectal temperature less than 108 °F during 6 hours of
continuous exposure were considered safe.

Results from the experiments provided data to fonmlate an equation used in
defining the tolerance index. Increasing the environment's humidity serves as

a catalyst in decreasing a dog's tolerance to heat. In order to offset the effects
of an increase in air temperature (starting at 85 °F with a 90 percent relative
humidity), relative humidity would need to be decreased by 4 percent for every

1 °F rise in temperature. Changes in rectal temperature and behavior (barking

and excessive movement) in relation to the exposure environment are presented and
discussed.

Partial funding for this study was provided by the United States Department of
Agriculture under an interagency cooperative agreement.

17, Key Words 18. Distribution Statement

Heat/humidity, Environmental stress, Document is available to the public

Animal physiology, Temperature/humidity through the National Technical

tolerance index, Beagle dogs, Animal Information Service, Springfield,

transportation Virginia 22161.

19. Security Clossif. (of this report) 20. Security Classif, (of this page) ZI. No. of Pages | 22. Price
Unclassified Unclassified 17

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized

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Equation [3] is used to determine a tolerance less than 100
percent (when x falls between 0 and 60). A tolerance of less
than 100 percent means that it is expected that some percentage
less than 100 of the dogs exposed to that particular tempera-
ture/humidity combination would not be able to safely tolerate
the exposure as previously described.

By using the above equations, a tolerance index (Table 8
was developed to show the percentage of healthy adult dogs that
would be expected to safely tolerate the given high temperature
and humidity conditions during transport.

Discussion

It is easily understood how an increase in atmospheric
temperature can cause an increase in body temperature, especially
when the air temperature rises to near body temperature and
above. Humidity alone does not directly cause the body temper-
ature to rise. However, when the air temperature is near 80 F
and higher, high humidity can promote an increase in body
temperature by decreasing evaporative heat loss through open-
mouth panting (1). The net quantity of heat lost by evaporation
is an inverse function of the environmental temperature and
humidity (5).

Besides the usual problems induced by high temperature and
humidity, it must be recognized that what a dog experiences when
living in a typical hot/humid environment (e.g., at home, in the
shade, relaxed, with water available, and munching on morsels of
food) is not the same as the stressful confinement of a shipping
crate with restricted ventilation. We have observed that, under
nonstress conditions, a dog's rectal temperature can rise several
degrees Fahrenheit when it is first placed in a crate (even
though it has had previous experience being in the crate). If
the dog is allowed to relax with few outside disturbances, its
rectal temperature will return to normal levels, Some of the
observed dogs appeared to accept the confinement of the crate
more easily than others. While recording baseline data outside
the test chamber, we noted that some animals' acceptance seemed
to be related to their ability to maintain visual contact with
or awareness of the investigator who was seated several feet
away.

When the dogs were placed in the hot/humid environment of
the test chamber, many became disturbed and exhibited behavioral
responses, The two categories of recorded responses were barking
and excessive movement. Barking was transmitted by means of an
intercom between the chamber and outside. Excessive movement
(observed visually) was any movement other than normal postural
changes, such as pawing at the crate wall or floor, continuous
circling, slithering around the crate floor, and twisting/turn-
ing. For most dogs, this type of activity occurred more

14