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Influence of the Environment on Body Temperature of Racing Greyhounds


Abstract and Figures

Heat strain is a potential risk factor for racing greyhounds in hot climates. However, there have been limited studies into the incidence of heat strain (when excess heat causes physiological or pathological effects) in racing greyhounds. The aim of this study was to determine if heat strain occurs in racing greyhounds, and, if so, whether environmental factors (e.g. ambient temperature and relative humidity) or dog-related factors (e.g. sex, bodyweight, color) are associated with the risk of heat strain. A total of 229 greyhounds were included in over 46 race meetings and seven different race venues in South Australia, Australia. Rectal temperatures of dogs were measured pre- and post-race and urine samples collected for analysis of myoglobinuria. Ambient temperature at race times ranged between 11.0oC to 40.8oC and relative humidity ranged from 17% to 92%. There was a mean increase in greyhound rectal temperature of 2.1oC (range 1.1oC to 3.1oC). A small but significant association was present between ambient temperature and increase in rectal temperature (r2=0.033, P=0.007). The mean ambient temperature at race time, of dogs with post-race rectal temperature of or exceeding 41.5°C , was significantly greater than at race time of dogs with a post-race rectal temperature ≤41.5oC (31.2oC vs 27.3oC, respectively, P=0.004). When the ambient temperature reached 38oC, over one third (39%) of dogs had a rectal temperature >41.5oC. Over half of post-race urine samples were positive by Dipstick reading for haemoglobin/myoglobin, and of 77 urine samples positive for Dipstick readings, 95% were positive for myoglobin. However, urinary myoglobin levels were not associated with ambient temperature or post-race rectal temperatures. The mean increase in rectal temperature was greater in dark (black, blue, brindle) than light (fawn and white) coloured greyhounds. The results suggest heat strain occurs in racing greyhounds, evidenced by post-race rectal temperatures over 41.5oC and post-race myoglobinuria. Risk of heat strain may be increased in higher ambient temperatures and in darker coloured greyhounds. Further research into the incidence of heat strain in racing greyhounds, and longer term physiological responses to heat strain, are warranted.
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June 2016 | Volume 3 | Article 531
published: 30 June 2016
doi: 10.3389/fvets.2016.00053
Frontiers in Veterinary Science |
Edited by:
Mia Cobb,
Working Dog Alliance Australia,
Reviewed by:
Howard H. Erickson,
Kansas State University, USA
Nicholas Julian Branson,
Deakin University, Australia
Susan J. Hazel
Specialty section:
This article was submitted
to Veterinary Humanities
and Social Sciences,
a section of the journal
Frontiers in Veterinary Science
Received: 12April2016
Accepted: 17June2016
Published: 30June2016
McNichollJ, HowarthGS
and HazelSJ (2016) Inuence
of the Environment on Body
Temperature of Racing Greyhounds.
Front. Vet. Sci. 3:53.
doi: 10.3389/fvets.2016.00053
Inuence of the Environment
onBody Temperature of Racing
Jane McNicholl, Gordon S. Howarth and Susan J. Hazel*
School of Animal and Veterinary Sciences, University of Adelaide, Adelaide, SA, Australia
Heat strain is a potential risk factor for racing greyhounds in hot climates. However,
there have been limited studies into the incidence of heat strain (when excess heat
causes physiological or pathological effects) in racing greyhounds. The aim of this
study was to determine if heat strain occurs in racing greyhounds, and, if so, whether
environmental factors (e.g., ambient temperature and relative humidity) or dog-related
factors (e.g., sex, bodyweight, color) are associated with the risk of heat strain. A total
of 229 greyhounds were included in over 46 race meetings and seven different race
venues in South Australia, Australia. Rectal temperatures of dogs were measured
pre- and postrace and urine samples collected for analysis of myoglobinuria. Ambient
temperature at race times ranged between 11.0 and 40.8°C and relative humidity
ranged from 17 to 92%. There was a mean increase in greyhound rectal temperature
of 2.1°C (range 1.1–3.1°C). Asmall but signicant association was present between
ambient temperature and increase in rectal temperature (r2=0.033, P=0.007). The
mean ambient temperature at race time, of dogs with postrace rectal temperature of or
exceeding 41.5°C, was signicantly greater than at race time of dogs with a postrace
rectal temperature 41.5°C (31.2 vs. 27.3°C, respectively, P=0.004). When the ambi-
ent temperature reached 38oC, over one-third (39%) of dogs had a rectal temperature
>41.5°C. Over half of postrace urine samples were positive by Dipstick reading for
hemoglobin/myoglobin, and of 77 urine samples positive for Dipstick readings, 95%
were positive for myoglobin. However, urinary myoglobin levels were not associated
with ambient temperature or postrace rectal temperatures. The mean increase in rectal
temperature was greater in dark (black, blue, brindle) than light (fawn and white) colored
greyhounds. The results suggest heat strain occurs in racing greyhounds, evidenced
by postrace rectal temperatures over 41.5°C and postrace myoglobinuria. Risk of heat
strain may be increased in higher ambient temperatures and in darker colored grey-
hounds. Further research into the incidence of heat strain in racing greyhounds, and
longer term physiological responses to heat strain, are warranted.
Keywords: greyhound, heat strain, heat stress, animal welfare, myoglobin, sport
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
Regulation of body temperature is essential for maintenance of
life. Vertebrates regulate body temperature by both behavioral
and physiological means. In mammals, cutaneous thermal
sensors measure surface temperature, while core temperature
is measured in the spinal cord and areas of the brain (1, 2).
Heat stress describes the environmental or metabolic factors
impacting on the body when its thermoregulatory mechanisms
are challenged, due either to excessive ambient temperatures
or extreme heat production whereas heat strain is the result-
ant physiological or pathological eects (3). Heat stroke occurs
when the body’s heat dissipating mechanisms are overwhelmed
due to exposure to an environmental temperature exceeding
body temperature (classic or environmental heat stroke) or
when metabolic heat accumulates due to strenuous exercise
(exertional heat stroke) (4). Heat stroke entails major organ fail-
ure and is life threatening (5, 6). In climates with high ambient
temperatures, such as in Australia, heat stress and heat stroke
are potential risk factors for dogs used in work and recreation,
including the racing greyhound.
Dogs are able to maintain their temperature over a broad range
of environmental and climatic conditions. Dierent thermoneu-
tral zones have been estimated using a variety of methods and
types of dog. A range of 23–27°C has been suggested as thermo-
neutral for three mixed breed dogs with bodyweights 8.5–10.5kg
(7), while for Innuit dogs it is 25 tο 10°C (8). In greyhounds,
the thermoneutral zone has been estimated to be 16–24°C (9).
Symptoms of heat illness in dogs include panting, dry mucous
membranes, prolonged capillary rell time, ataxia, and elevated
body temperature (10, 11).
As greyhounds have been subject to intense selection for
athletic performance over several centuries (12, 13), and 60%
of the body mass is muscle (14), the large locomotor muscles
may contain high mitochondrial and capillary volumes as
found in some athletic marsupials (15). It could therefore be
expected greyhounds would generate heat at a high rate and be
particularly susceptible to exertional hyperthermia. Muscular
activity generates heat as a by-product of ATP production and
utilization. When the ambient temperature nears or exceeds
body temperature, heat can only be lost by evaporation, which
in dogs is achieved via the respiratory tract (16). During strenu-
ous exercise, the respiratory rate increases, thus facilitating heat
transfer, however, high levels of humidity may restrict the amount
of heat lost. Although the milder manifestations of heat illness
described in humans, such as heat rash and heat edema, have
not been described in dogs, more signicant symptoms such
as cramps and fatigue are commonly exhibited by greyhounds
following even short periods of strenuous exercise (17, 18). e
elevation in rectal and muscle temperature resulting from pro-
longed exercise by dogs is associated with reduced levels of high
energy phosphates (ATP and CrP) and increased levels of muscle
lactate, pyruvate, and AMP, which may contribute to fatigue (19).
Although greyhounds racing in environmental temperatures of
42°C are thought to be at risk of heat stroke (20), there has been
little research into the eects on greyhounds of running in high
ambient temperatures.
Heat stroke has been recognized for centuries, but until rela-
tively recently the mechanisms were poorly understood. Shapiro
et al. (21) was able to demonstrate, using dogs (which do not
sweat), that heat stroke was due to tissue damage resulting from
elevated body temperature and not cessation of sweating as had
been previously believed. A subsequent study in which anesthe-
tized dogs were heated to a rectal temperature of 44.5°C, revealed
increased levels of serum enzymes such as glutamic-pyruvic glu-
taminase (SGPT) and alkaline phosphatase in the terminal stages
of hyperthermia, indicative of tissue damage (22). e authors
also noted necrosis of liver and intestinal epithelium and turbid,
brown urine, indicative of impaired renal function. Current
understanding is that heat stroke involves impairment of cellular
function, denaturing of proteins (both structural and enzymatic)
and disruption of lipid membranes, similar to systemic inam-
matory response syndrome (SIRS) (23). Hyperthermia induces
intestinal ischemia and increased intestinal wall permeability,
which permits leakage of endotoxins (10, 24).
Rhabdomyolysis (muscle breakdown) may be a consequence
of both strenuous exercise (25, 26) and heat strain (27). Exercise-
induced muscle ber damage has been reported in humans (28)
and animals (2932). Following rhabdomyolysis, there is rapid
release of cell breakdown products, such as the enzymes creatine
kinase and lactate dehydrogenase; ions such as potassium and
phosphate and muscle proteins such as myoglobin (25, 33).
Muscle ber damage may be detected by the presence of myoglo-
bin in urine (myoglobinuria) (33). Myoglobin is nephrotoxic and
in humans, elevated levels of myoglobin in serum or urine are
associated with a risk of acute renal failure and subsequent mor-
tality. Myoglobinuria has been reported in greyhounds (34) but
the incidence is unknown and the levels of myoglobin excreted
have not been quantied.
Dehydration has been identied by many authors as a precur-
sor or precipitating factor for heat stroke in humans (35, 36). It
has been widely accepted that dehydration of 2–3% is a major risk
factor for heat illness and that a uid decit of as little as 1.5–2%
may have a negative eect on performance (37). A decrease in
plasma volume of 6±2% increases the rate of heat accumulation
in dogs exposed to high external heat load (38); furthermore, a
signicant elevation in rectal temperature occurs in dehydrated
versus non-dehydrated dogs exercising on a treadmill at 25°C
(39). Racing greyhounds may lose up to 6% of their bodyweight,
due to dehydration, in the prerace kenneling period (40). Such
losses might lead to increased risk of hyperthermia and increased
risk of renal damage from myoglobinuria.
Phenotypical factors, such as sex and bodyweight, may also
inuence the response of greyhounds to environmental condi-
tions. Sex-based dierences in response to elevated temperatures
and exercise occur in humans (41) and mice (42). Dierences
exist in the susceptibility of male and female rats to disrup-
tion of the sarcolemma following exercise (43), and there are
apparent protective eects of estrogen against exercise-induced
muscle damage in rats and humans (44, 45). Sex dierences in
susceptibility to exertional rhabdomyolysis in dogs have not been
reported. Body weight is also important, as the basal metabolic
rate of mammals and resultant heat production increases with
bodyweight (46). With an increase in body mass there is a
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
reduction in the ratio of body surface area to body mass and an
increase in the distance from core to surface: both of these factors
reduce the ability of an animal to dissipate heat and in exercising
animals, may lead to greater heat accumulation (47). Finally, coat
color is important as there is a widely held lay opinion that black
greyhounds are more stressed by high ambient temperatures than
other colored greyhounds, a belief which might be supported by
studies in other species. e white winter coats of arctic species
have greater reectivity than darker summer coats (48) and in
cattle, white coat color increases heat tolerance over brown or
black (49).
Since this study is performed in Australia, it is important to
provide some background on greyhound racing in this country.
Greyhound racing is conducted in all Australian states and ter-
ritories, each of which has a governing body, which administers
and regulates racing. e population of racing greyhounds in
South Australia is approximately 60% male and 40% female (T.
Hayles, GRSA personal communication, June 2013). Sex limited
races for greyhounds are seldom programed so the majority of
races include animals of both sexes. Greyhounds commence
racing at or above 16months of age and generally have a rac-
ing career of 18–24 months, thus racing greyhounds have a
relatively narrow age span of approximately 2–4years of age.
Five basic coat colors are recognized: black, blue (a dilute of
black which can be pale to dark gray), brindle (dark stripes over
a base color producing black brindle, blue brindle, red brindle,
dun brindle, fawn brindle, dark brindle, light brindle), fawn
(dark fawn, light fawn, red fawn, blue fawn, or dun fawn), and
dun which may range from a light blue fawn, through a rich red
fawn, to a deep rich chocolate color, with the dominating factor
being a pink to brown colored nose leather. Dun is extremely
rare. Any of these colors may be distributed over the body in
patches over a white base, and such greyhounds are described
as parti-colored.
No studies to date to our knowledge have investigated body
temperature changes in greyhounds during racing in Australia.
Furthermore, it is not known if potential risk factors, such as sex,
body weight, or coat color, may alter the risk of heat strain. e
aims of this study were to determine if:
1) body temperature increases more in greyhounds raced during
hot and during humid days;
2) body temperature is inuenced by dog sex, body weight, coat
color, or cooling vest use;
3) myoglobin is present in urine in greyhounds following racing,
4) if myoglobin is present, if levels are aected by ambient tem-
perature, race distance, dogs’ level of tness, sex, body weight,
or postexercise rectal temperature.
An observational study was commenced in 2010 to record
temperature and humidity at racing venues around South
Australia and to record body temperature changes of greyhounds
competing in races. e climate of the more populated districts
of South Australia is described as Mediterranean with cool wet
winters and hot dry summers (50). In summer, mean maximum
daily temperature for the capital city, Adelaide (Latitude 34°
50S–Longitude 138° 30E) is 29°C (51). Animal ethics approval
was provided for this study by the University of Adelaide Animal
Ethics Committee.
Ethic Statement
Owners or trainers gave informed signed consent at the racetrack
to participate in the study.
e pool of racing greyhounds in South Australia uctuates,
as dogs commence or terminate their racing careers and move
between states. Across Australia in 2011, there were 43,259 races
organized in 4068 race meetings and over $82,000,000 (AUS)
prize money was distributed: the greyhound industry had 12,280
greyhounds registered for racing for a total of 330,429 starters
(Greyhounds Australasia 2011). In South Australia, greyhound
racing is controlled by Greyhound RacingSA (GRSA) and the
industry represents over 16% of Totalizer Agency Board (TAB)
market share and distribution, which in 2010–2011 was $10m
(AUS) (52).
Racing is conducted throughout the year. At the time of com-
mencement of this study, there were eight racetrack venues, three
of which (Barmera, Port Augusta, and Virginia) did not conduct
race meetings during January and February. All racetracks with
the exception of Virginia were oval tracks. e Virginia track was
straight and only held lure coursing events. Race meetings were
conducted three times per week at both Angle Park and Gawler
but at approximately fortnightly intervals at other tracks.
On oval tracks, 7–12 races are programed per meeting and
eight greyhounds (plus two reserves) are drawn to compete in
each race. At lure coursing meetings, 6–10 events are held, each
of which include 4–32 runners drawn to run o in pairs. Winners
of each course proceed to the next round until the surviving pair
contested a nal. At the Virginia straight track, lure coursing
meetings are only held between April and October and meetings
commenced at 9.30a.m. and nished by 2p.m. At other tracks,
races are scheduled between 12 p.m. and 11 p.m. and all grey-
hounds engaged at a meeting are presented for inspection prior
to kenneling and kenneled at least 30min prior to the rst race
on the program.
Pre-kenneling inspection entails an identity check of each
greyhound by color, markings, ear tattoo, and/or microchip
number. Every greyhound is then weighed and undergoes a brief
veterinary inspection for health and racing suitability. Following
inspection, each greyhound is conned in an allocated kennel
until approximately 10min prior to its race start time. At the
Virginia racetrack, greyhounds are conned in their transport
vehicles for the duration of the meeting.
Forty-six race meetings were attended at seven dierent
venues and at dierent times of the year (Tab l e1 ). One track was
straight (Virginia), and the other six were oval with various radii
and circumferences. Two race tracks (Port Augusta and Virginia)
have grass surfaces and ve (Angle Park, Barmera, Gawler, Port
Pirie, and Strathalbyn) have sand/loam surfaces. Races were
conducted over distances of 300–731m.
TABLE 1 | Racetrack venues attended during 2011.
Track January February March April May June July August September October November December
Angle Park 1 3 2 1 1 1 4
Gawler 7 3 3 1 1 2 1 2
Strathalbyn 2 2
Barmera 1 1 1 1 1
Port Pirie 1
Port Augusta 1
Virginia 1 1
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
Environmental Monitoring
Ambient conditions inside the kennel houses and trackside were
monitored with a weather station (La Crosse Technology, wireless
433-MHz Weather Station). Kennel house conditions were meas-
ured by the monitor placed approximately 1.2m above ground
level in the kennel area. Trackside conditions were measured by
the outdoor monitor placed 1.2–1.8m above ground level adja-
cent to the track, at a readily accessible location. Temperature and
relative humidity were manually recorded at the start time of each
race in which a selected greyhound was competing. Cloud cover
was recorded in oktas on a scale 0–8 on which 0=nil cloud and
8=complete cloud cover (53). Some races were conducted aer
dusk, which was recorded as 10.
Temperatures were measured using a rectal clinical veterinary
thermometer (Vicks Speed Read digital thermometer).
Cooling Jackets
e use of cooling jackets on greyhounds at racetracks, in tem-
peratures >30°C, has been encouraged by GRSA for over 4years
(P. Marks, personal communication, January 2014). e jackets
used during this study (Cool Champions, Silver Eagle Outtters were soaked in iced water for
30min prior to initial use and also between uses.
e population of racing greyhounds in South Australia is
approximately 1200 animals (G. Barber, GRSA personal com-
munication, January 2010). On the day prior to a race meet-
ing, the elds were accessed online at
au and greyhounds were selected by random draw using Excel
RANDBETWEEN function. If two greyhounds in the care of one
trainer at one meeting were selected, a draw was repeated to select
an alternative greyhound. Details of the age, sex, color, sire, dam,
and previous race history of each greyhound were recorded from
the published race elds.
For the purpose of this study, greyhounds were assigned a t-
ness score expressed in meters from 300 to 700m in 100-m incre-
ments. e tness score was based on the mode of the greyhounds
last three races or trials to the nearest 100m. From 246 races, 238
greyhounds were selected to participate in the study (134 males,
104 females) aged 18months to 5years (mean 2.6years). In the
greyhound industry, the generally accepted desirable weight
range for racing dogs is 26–34kg, for the purpose of analysis,
the greyhounds were divided by bodyweight into four groups
commonly used in the industry: <26, 26–30, >30–34, >34 kg.
Any dog in with more than 50% white coat color was classied as
white, thus creating ve color groups (Figure1). One greyhound
was selected three times, and six greyhounds were selected twice.
For the purpose of analysis, each of these greyhounds race starts
was treated as a separate data point.
At each race meeting, approximately 30min prior to the com-
mencement of greyhound admission, a list of selected grey-
hounds was provided to the stewards and a copy was posted in a
prominent position at the kennel house entrance. As the selected
greyhounds were presented for identication checks, the trainer
was advised of the selection and permission sought for inclusion
in the study. Some trainers declined to include some of the pre-
selected greyhounds because of perceived temperamental unsuit-
ability. Each participating greyhound was weighed and then had
its temperature recorded as arrival temperature. Greyhounds
were subsequently conned in their allocated kennels (or at lure
coursing meetings, in trailers) up until approximately 10min
prior to their race start time.
Each greyhound was then collected from its allocated kennel
and had a racing vest tted, underwent identity check by stewards
and was then taken outdoors to relieve itself. Urine samples were
collected by voluntary voiding from 182 greyhounds. Rectal
temperature was then recorded (prerace temperature). Aer
completion of a race, greyhounds were collected by their handlers
and returned to the kennel house and each greyhound’s tempera-
ture was again recorded (postrace temperature). is time point
was between 2 and 3min aer greyhounds ceased to run. All
greyhounds then underwent hosing and were allowed to drink
from a hose prior to being returned to their allocated kennels.
e greyhounds, which competed in lure coursing events, were
assessed aer two courses, which were conducted at least 30min
apart, during which time the greyhounds were lightly hosed with
cold water, oered cold water to drink, and conned in well ven-
tilated trailers, thus permitting cooling. An attempt was made to
follow up each greyhound to collect a second urine sample before
the greyhound le the racetrack. Postrace urine samples were
collected from 203 greyhounds. Rectal temperature before and
aer racing was obtained for 229 dogs (131 males, 98 females).
Matched pre- and postrace urine samples were collected by
voluntary voiding from 177 greyhounds, 104 males, 73 females:
FIGURE 1 | Greyhound colors: (A) black, (B) blue, (C) fawn, (D) brindle, (E) parti-colored white and brindle, (F) parti-colored white and black.
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
(a) in the immediate prerace exercise period, and (b) as the
greyhounds were leaving the track. Postrace samples were
obtained between 30 min and 3 h aer racing, dependent on
the trainer’s schedule. Urine samples were transferred from
the collecting ladle into specimen containers immediately aer
collection and placed on ice for transport, then refrigerated up
to 12 h prior to screening. Urine samples were centrifuged at
3000rpm for 5min to remove red blood cells. Reagent strips
(Siemens Multistix 10 SG) were then immersed in the super-
natant urine and read following the manufacturer’s protocol.
Results for blood/hemoglobin are expressed as trace, 1+, 2+,
3+ (1+ equivalent to 0.030–0.065 mg/dl). e manufacturer
states the test is equally sensitive to myoglobin and hemoglobin.
Samples were then stored frozen at 20°C for up to 12months.
Subsequently, 87 urine samples (77 which tested positive for
blood/hemoglobin, 7 which tested negative and 3 unknown)
were thawed and subjected to enzyme linked immunosorbent
assay (ELISA) using Dog Myoglobin (Life Diagnostics, Inc.) and
read at 450nm (Benchmark Plus BIO-RAD).
Data Analysis
Data for the analysis of rectal temperature changes and associa-
tions with ambient temperature and humidity was analyzed with
GraphPad Prism 6. Linear regression analysis was conducted to
determine the association between shade temperature and rela-
tive humidity on rectal temperature at three time points: (a) on
arrival; (b) pre-race; and (c) postrace. Linear regression analysis
was also used to determine any association between ambient
temperature, race distance, dogs’ level of tness, bodyweight, and
postexercise body temperature and postexercise urine levels of
myoglobin. Data were inspected for normality in distribution
using the D’Agostino–Pearson test. Unpaired t-tests with Welches
correction were conducted to determine sex-based dierences in
urine myoglobin, and the eects of cooling jackets worn postrace.
Statistical analyses to analyze eects of dog sex, weight, and
color on rectal temperature changes were conducted using SPSS
version 21. Data were inspected for normality in distribution using
the D’Agostino–Pearson test. A mixed model which included the
xed eects of sex and color and covariate of weight and sire as a
random term was tted to the increase in rectal temperature and
the postrace rectal temperature data. ere was no sire variance
thus a general linear model was tted to the data with the above
xed eects and covariate. Any signicant two-way interactions
were retained in the model. A level of signicance of P<0.05 was
used throughout.
Environmental Conditions
Ambient (shade) temperature at each dog race start ranged from
11.0 to 40.8°C. Relative humidity ranged between 17 and 92%.
As ambient temperature increased, relative humidity decreased
(Figure2, r2=0.64, P=0.0001).
Body Temperature
Mean rectal temperature of 229 greyhounds on arrival at the race
meetings was 39.2°C±0.5°C (range 38.2–40.5°C). Postrace, there
was an increase in rectal temperature in all dogs. Mean postrace
temperature was 41.0±0.5°C (range 39.7–42.1°C) with a mean
increase of 2.1°C (SD 0.4°C, range 1.1–3.1°C; Figure3).
ere was no signicant eect of shade (ambient) temperature
on rectal temperature on arrival (r2=4.5×107, P=0.99). Postrace
there was a small but signicant relationship between shade tem-
perature and both rectal temperature (r2=0.023, P=0.03) and
increase in rectal temperature (r2=0.033, P=0.007; Figure4).
A signicant inverse relationship between prerace rectal tem-
perature and the increase in rectal temperature aer racing was
determined (r2=0.15, P=0.001).
FIGURE 3 | Increase in rectal temperature from pre- to postrace in
229 greyhounds.
FIGURE 2 | Relationship between ambient temperature and relative
humidity recorded at racetracks (r2=0.64, p=0.0001).
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
Effect of Relative Humidity
ere was no signicant association between relative humidity
and postrace rectal temperature (r2=0.02, P=0.06).
Effect of Race Distance
No association between race distances and levels of postrace
rectal temperature was found (r2=0.004, P=0.4).
Effect of Dog Fitness
No association was detected between dogs’ levels of tness and
levels of postrace rectal temperatures (r2=0.001, P=0.7).
Cooling Jackets
Dogs that wore cooling jackets (N=41) had a signicantly higher
rectal temperature postrace compared to those that did not
(N=80; mean 41.19±SEM 0.06°C versus 41.01±SEM 0.06°C,
respectively, P=0.04; unpaired t-test with Welch’s correction).
Critical Temperatures
As 41.5°C has been suggested as a critical body temperature for
precipitating heat illness in dogs (11, 54), animals were allocated
into two groups using a postrace rectal temperature delimiter of
>41.5°C. e mean ambient temperature at race time of dogs with
postrace rectal temperature >41.5°C was signicantly greater
(31.2°C±SEM 1.0°C, N=40) than at race time of dogs record-
ing a rectal temperature 41.5 (27.3°C±SEM 0.5°C, N=189,
unpaired t-test, t=2.9, df=227, P=0.004).
e percentage of greyhounds with postrace rectal tem-
peratures of >41.5°C was plotted against ambient temperature
(Figure 5). When the ambient temperature was 38°C, 39% of
dogs had a rectal temperature of >41.5°C.
In both males and females, over half (100/177, 57%) of postrace
urine samples provided positive dipstick readings for hemo-
globin/myoglobin (Tables 2 and 3). ere were more positive
dipstick results for males versus females.
Myoglobin levels detected in postrace urine samples ranged
from 3 to 402 ng/ml (mean 93.3 ± 8.6 ng/ml). A signicant
association between dog bodyweight and myoglobin levels was
detected (r2=0.05, P=0.05). As variances of male and female
myoglobin levels diered (P=0.0003) an unpaired t-test with
Welches correction was conducted. A signicant dierence
in myoglobin levels between males and females was detected
(male 73.17±SEM 7.76ng/ml, female 128.20±SEM 20.15ng/
ml, P=0.01). Linear regression analysis showed no signicant
associations between urinary myoglobin levels and ambient
temperature, race distance, level of tness, or postrace rectal
Effect of Greyhound Color
e most common coat color of the included greyhounds was
black (N= 115), followed by white (N= 37), with similar
numbers of blue (N= 23), Brindle (N= 28), and Fawn
(N=26) colors. ere was no signicant dierence in arrival
or prerace rectal temperature of the ve color groups (P=0.5).
However, mean postrace temperatures of the black, blue, and
brindle greyhounds were 41.1 ± 0.4°C, 41.1 ± 0.5°C, and
41.1±0.4°C, respectively, which were signicantly higher than
the fawn (40.9±0.5°C) and white (40.8±0.5°C; all P<0.05)
greyhounds. When the dogs were grouped into dark (black,
blue, brindle) and light (fawn and white), the mean increase
in temperature of the dark-colored dogs (2.2 ± 0.4°C) was
signicantly greater than the mean increase in temperature
of the light-colored dogs (2.0 ± 0.4°C, P= 0.005). Postrace
rectal temperatures of greyhounds racing in fully overcast/
dark conditions (N=31), or sunlight (N=131) showed no
signicant dierence (P=0.5).
Effect of Sex
ere was no signicant sex-related dierence in arrival rectal
temperature for 128 males and 101 females (P=0.897). Prerace
temperatures for males (N= 132) and females (N= 100) also
did not dier (38.9 ± 0.5°C versus 38.8°± 0.3°C respectively,
P=0.46). A signicant dierence was found in postrace rectal
temperature of male (N=131) and female (N=98) greyhounds
(P=0.004). Mean male postrace temperature was 41.1±0.5°C,
and mean female postrace temperature was 40.9±0.4°C.
TABLE 3 | Myoglobin results from 87 greyhound urine samples.
Dipstick test result Positive
Positive blood/hemoglobin 77 73 (95%) 4 (5%)
Negative blood/hemoglobin 7 3 (43%) 4 (57%)
Unknown blood/hemoglobin 3 2 (67%) 1 (33%)
aThe lowest positive value was 5.8ng/ml.
TABLE 2 | Results of dipstick test for blood, hemoglobin, or myoglobin in
postrace urine samples.
Screened Total positive
Male 104 70 (67%) 47 (45%)
Female 73 30 (41%) 24 (33%)
FIGURE 5 | Relationship between ambient temperature and the
percentage of greyhounds with postrace rectal temperature >41.5°C.
FIGURE 4 | Relationship between ambient temperature and: (A) postrace rectal temperature and (B) increase in rectal temperature.
TABLE 4 | Sex distribution in four body weight groups of selected
<26kg 26–30kg >30–34kg >34kg
Male Female Male Female Male Female Male Female
0 23 10 68 82 7 39 0
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
Effect of Bodyweight
In the greyhound industry, the generally accepted desirable weight
range for racing dogs is 26–34kg: 73% of the selected greyhounds
were within this range. e mean bodyweight was 30.2±3.4kg.
Mean male bodyweight was 32.5kg (median 32.0kg), and mean
female bodyweight was 27.2kg (median 27.0kg). ere were no
males in the <26kg weight group, and no females in the >34kg
weight group (Table4).
A signicant eect of bodyweight was noted on both actual
rectal temperature (r2= 0.043, P= 0.009) and the increase
in rectal temperature (r2=0.05, P=0.006) following racing
e aims of the current study were to determine the body temper-
ature responses to racing in greyhounds in South Australia. e
study was designed to determine changes in rectal temperature
following racing, and if any associations were present between
increase in rectal temperature and environment factors, such
as ambient temperature and relative humidity, and dog-related
factors, such as sex, bodyweight, and color. Urinary myoglobin
was measured postrace to determine if any pathological changes
occurred and were related to heat strain.
In the current study, greyhounds competed in temperatures
between 11 and 40°C. e mean increase in rectal temperature
of 2.1°C was remarkable in view of the short duration of the
periods of exercise. Although, as greyhounds expend almost as
much energy in the rst 7.5 s of a race as in the subsequent
22 s (55), it is not surprising that body temperature increases
markedly in a short period of time. Although dierences of
up to 2°C between muscle and rectal temperatures have been
measured in horses aer 50-min exercise (56), the dierence
was less than 1°C aer 10 min exercise as completed by the
greyhounds in this study. Indeed in dogs, postexercise rectal
temperatures higher than core temperature may result from
the heat generated by the major muscles of the hind quarters
(57). Most of the studies on hyperthermia in human and equine
FIGURE 6 | Relationship between bodyweight and (A) postrace rectal temperature (r2=0.043, P=0.009) and (B) increase in rectal temperature
(r2=0.05, P=0.006) after racing.
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
athletes have focused on hyperthermia as a result of prolonged
periods of exercise. However, Drobatz and Macintyre (58) in
their review of 42clinical cases of heatstroke in dogs, remarked
on the degree of morbidity aer relatively short (20–30min)
periods of exercise, suggesting a high degree of susceptibility for
dogs, compared to other species. As heat storage has been shown
to be the principle limiting factor to intense exercise in cheetahs
(59), it is probable that heat storage might similarly be a limiting
factor to sprinting performance in greyhounds.
In the current study, the period of strenuous exercise was
between 15 and 45s for distances from 300 to 730m. Additional
activity was low intensity and was restricted to a total period of
<15min during which greyhounds were removed from holding
kennels, approximately 10 min prior to scheduled race start
time and walked to the starting boxes, 2min prior to the race.
Greyhounds exhibited varying levels of excitement in the prerace
period, demonstrated by ne tremors or vigorous activity such
as pulling or bouncing. e muscular activity involved in such
behavior would generate heat and may have contributed to the
increases in rectal temperature recorded. Greyhounds, bred and
trained for racing, may develop an increase in rectal temperature
(from resting levels) due to anticipation of activity (60). e nega-
tive association between prerace rectal temperature and increase
in rectal temperature found in the current study illustrates the
eectiveness of the thermoregulatory system, even under signi-
cant challenge.
Environmental Conditions
e current study revealed a small but positive association between
ambient temperature and postexercise body temperature. ese
ndings are in accord with those of Bjotvedt et al. (20) where
greyhounds performing in temperatures above 107°F (42.0°C)
were at risk of heat stroke. Although intense exercise is generally
estimated to cause an increase in metabolic rate of 10–14 times
the basal metabolic rate (61), increases in metabolic rate of up
to 25 times BMR have been recorded in some canine species (8,
62). Dissipation of the heat generated may pose a particular chal-
lenge. Susceptibility to heat illness may vary between breeds of
dog as ambient temperature has not been shown to aect rectal
temperature in exercising Labrador retrievers (63), although the
Labradors were only exercised in a temperature range of 11–28°C.
In contrast, a signicant association between ambient tempera-
ture and rectal temperatures is present in sled dogs working in
ambient temperatures between 9 and 25°C (64).
No signicant eect of relative humidity on rectal temperature
was demonstrated in the current study. However, as the climate
of South Australia is described as Mediterranean (50), with an
inverse relationship between temperature and humidity, days
with concurrent elevation of both factors are rare. In areas with
a tropical climate, humidity might impose greater challenges. In
exercising horses, the rate of increase in temperature of blood,
measured in the pulmonary artery, is signicantly higher in hot,
humid conditions than in either hot or cold, dry conditions (65).
It may be concluded that racing, or undertaking equivalent
intense exercise, in hot weather carries an increased risk of
greyhounds developing heat illness. e risk increases notably
in ambient temperatures 38°C. However, under current
management systems in South Australia, no racing greyhounds
were found to suer from heat stroke. e greyhound racing
industry in Australia has a number of “Heat” or “Hot Weather”
policies, which vary between states and lack a consistent thresh-
old temperature. It would be prudent to set the threshold for
“Hot Weather Policies” at 38°C, at which temperature, changes
to race programing should be made and stringent management
procedures be implemented for greyhounds participating in
races or trials.
Critical Temperature
Many authors consider a rectal temperature 41.5°C to be a criti-
cal level for initiation of heat illness in dogs (11, 54, 58, 66, 67).
During the current study, 45 greyhounds recorded a postrace
rectal temperature >41.5°C which if not reduced, would place
them at risk of heat illness. e mean ambient temperature at
the time of these races was 31.2°C, which was 4°C greater than
the mean ambient temperature at race time for greyhounds
recording a rectal temperature <41.5°C. erefore, 31°C might
represent a threshold for risk estimation for heat stress in racing
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
greyhounds. Such a threshold might be broadly accepted by
participants in the greyhound racing industry, as there is a com-
mon perception amongst trainers of greyhounds that, at ambient
temperatures >30°C, the animals show signs of thermal stress
such as panting, which concurs with evidence from experimental
settings (68). However, as in South Australia there are more than
80days in summer with maximum daily temperature >30°C (51)
setting 31°C as a threshold for canceling race meetings would
represent major disruption to the industry. It has been suggested
36°C is the temperature at which thermal equilibrium can only
just be maintained by dogs (69). In the current study, the per-
centage of greyhounds recording postrace rectal temperatures of
41.5° increased in gradual linear fashion up to 36°C and with
a sharp rise when ambient temperatures reached 38°C. As 38°C
is within the normal range of body temperature for dogs, the
sharp increase in the number of greyhounds with temperature
>41.5°C when ambient temperatures neared 38°C is in accord
with the widely accepted view that, in environments at or above
body temperature, thermoregulation is dicult.
Cooling Jackets
e use of cooling jackets on greyhounds at racetracks has
been fairly limited. During the current study, there appeared to
be reluctance by some trainers to use them, either because of a
belief that they were uncomfortable for the dogs or because of a
perception the time taken to don the jackets was wasted. Results
of this study revealed the unexpected nding that the mean rectal
temperature of dogs wearing jackets postrace was slightly higher
than those dogs which did not. Cooling jackets of a dierent
type have been demonstrated to be eective in reducing the
duration of postexercise hyperthermia in military dogs (70). Pre-
competition use of ice jackets has been eective in reducing the
degree of body heating in human athletes (71), but postexercise
use of ice jackets is not advantageous in hyperthermic athletes
(72). Further research into their use in greyhounds during hot
conditions is warranted.
Alternative methods of estimating thermal stress in racing
greyhounds might include panting score such as used for sheep
(73) and cattle (49). However, in dogs panting is utilized not only
to maintain homeothermy (74) but also as a result of exercise
(19,75), arousal (60), or anxiety (76). As this study was conducted
at racetracks, all of the above factors could have inuenced pant-
ing rate, and it was not practical to utilize panting rate as an
indicator of heat stress.
Rhabdomyolysis has been recorded as a result of strenuous
exercise in greyhounds (77, 78) and rhabdomyolysis may also
result from hyperthermia (79). It could therefore be expected
that greyhounds undertaking strenuous exercise in hot condi-
tions would be at increased risk of developing rhabdomyolysis
and myoglobinuria. Myoglobin is a small heme protein, which
is released into plasma aer muscle ber rupture; plasma levels
fall rapidly, as it is excreted into urine (79). As myoglobin
is recognized as being nephrotoxic (33), it is possible that
repeated exposure to signicant levels would have a cumula-
tive eect and that such exposure might contribute to the
high incidence of renal disease seen in greyhounds (D. Fegan,
personal communication, 2013).
Effect of Phenotypic Factors
is study showed that postexercise temperature was inuenced
by several phenotypic factors. A signicant though weak rela-
tionship was found between bodyweight and postexercise rectal
temperature and also between bodyweight and the increase in
rectal temperature. Coat color was also found to have a signi-
cant association with postexercise temperature, with greyhounds
of dark colors developing higher rectal temperatures than light
colored greyhounds. Many greyhound trainers believe that black
greyhounds are more susceptible to heat stress than other colored
dogs, as the trainers can feel temperature dierences on the sur-
face of their greyhounds. e nding that dark colored (black,
blue, brindle) greyhounds develop higher temperatures than
light colored (fawn and predominantly white) greyhounds is in
keeping with ndings in other species. ree naturally occurring
color morphs of antelope have dierences in core temperature
(80) and McManus et al. (82) who examined the tolerance of
dierent breeds and colors of sheep, to heat stress in Brazil,
concluded that breed, coat type (wool/hair) and coat color were
important modiers. A number of studies of production animals
have revealed that, under heat stress, white coated animals can
maintain lower body temperatures than dark colored conspecif-
ics and that coat color inuences heat tolerance (81, 82). is
has been attributed to the greater reectivity of the white coats,
leading to less heat accumulation. In the current study, it was
anticipated that dark coated greyhounds, racing in sunlight, might
develop higher body temperatures than those racing in shaded
or dark conditions, however no signicant eect of sunlight was
detected. It seems therefore, that direct solar radiation was not a
signicant contributor to the temperatures recorded. However,
thermal radiation from the track surface and surroundings may
have contributed to the higher temperatures recorded in dark
coated dogs.
No signicant dierences between sexes were recorded for
rectal temperatures either on arrival or prerace. However,
males had higher postrace and mean increases in rectal
temperature than females. Sex based dierences in body
temperature could be a result of sex hormones, body propor-
tions, or thermoregulatory mechanisms. Gender dierences
in response to thermal and exercise challenges have been
reported in humans (41, 83). e principle mechanism of heat
loss in humans is sweating and considerable eorts have been
directed at examining dierences in sweating and sudomotor
responses (84, 85). However, as sweating is not utilized as a
heat loss mechanism in canines, it is not valid to attempt to
extrapolate from such studies. e inuence of estrogen and
progesterone on core temperature during the menstrual cycle
of women has long been recognized (86). Complex interactions
between norepinephrine and estrogen occur in the brain of
women, whereby estrogen raises the sweating threshold and
norepinephrine narrows the thermoneutral zone by initiating
heat dissipation (87). Hanada et al. (42) identied receptor
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
activator of necrosis factor kB ligand (RANKL) and its tumor
necrosis factor receptor (RANK) as key factors of central
control of thermoregulation in female but not male mice and
suggested that, in murine species, female thermoregulation is,
in part, regulated by ovarian sex hormones (42).
e higher levels of myoglobinuria found in female grey-
hounds was unexpected, as it has been reported that female
animals suer less muscle damage than males (88). However,
female horses are reported to be more frequently aected by
exertional rhabdomyolysis than males (89, 90). Female rats
are less susceptible to exercise-induced muscle damage than
males (43, 91), likely due to a protective eect of estrogen (92).
However, similar protection is unlikely to have occurred in
greyhounds during the current study as testosterone proprionate
was permitted to prevent estrous in female greyhounds at that
time (93). In Australia, female greyhounds are not permitted
to race whilst in estrous or for 28days post estrous (93) and
reduced performance in the diestrous period of up to 91days has
been reported (94). erefore, racing female greyhounds can be
assumed to be in late diestrous or anestrous with relatively low
levels of circulating estrogen and progesterone (95). Alternatively,
there may be a species related dierence in response to exercise
or even a breed specic response, as greyhounds exhibit other
physiological and hematological variations from other breeds of
dog (9698). During the current study, no data were collected
on the use of testosterone or other permitted hormones nor on
the natural hormonal status of the females, so further studies
on the responses to exercise of male and female greyhounds are
Many of the studies on thermoregulation and exercise in humans
have investigated the dierences, which might be attributable
to anthropometric features such as body proportions and fat
distribution (69, 99, 100). Lean animals may dissipate heat more
readily than obese animals, as in the latter, sub-cutaneous fat
impedes heat transfer to the environment (101). However, during
exercise, both muscle and core temperature increase more in lean
than obese rats (102). Almost all of the greyhounds in this study
had a body condition score of 2 and variations in body fat are
unlikely to have aected the results.
e positive associations between bodyweight and both
postrace and increase in rectal temperature may be attributed
to the amount of energy utilized during activity. As the energy
requirements to move a body increase with an increase in
bodyweight (103), metabolic heat production also rises. In both
birds and mammals, the energetic cost of exercise is related to
both body mass and speed (104, 105). In humans, metabolic heat
production resultant from muscle contraction creates an internal
heat load proportional to exercise intensity (106, 107). Although
the periods of exercise of the greyhounds were limited to <45s at
maximum eort, as greyhounds have a high proportion of muscle
(14) and the rate of heat accumulation in muscle increases with
intensity of work (47), it is apparent that greyhounds exercising
at maximum eort generate a very high heat load. In a recent
study, rats selected for high capacity running, exhibited high
levels of energy expenditure and muscle heat dissipation (108).
e authors suggested that these eects might be due to intrinsic
aerobic capacity and that similar expression of skeletal muscle
proteins might be found in other species. Greyhound muscle
exhibits a high rate of anaerobic glycogenolysis (109); further
research is warranted in the area of greyhound muscle energetics
and heat production.
It may be concluded that racing, or undertaking equivalent
intense exercise, in hot weather carries an increased risk of
greyhounds developing heat illness. e risk increases notably
in ambient temperatures 38°C. Large, dark-colored greyhounds
are at greater risk of developing high body temperature than
small, light-colored greyhounds, when undertaking strenuous
exercise in hot conditions. Pre- and postexercise cooling should
therefore be applied with particular care to large black, blue,
or brindle greyhounds to prevent development of heat strain.
e greyhound racing industry in Australia has a number of
“Heat” or “Hot Weather” policies which vary between states and
lack a consistent threshold temperature. It would therefore be
prudent to set the threshold for “Hot Weather Policies” at 38°C,
at which temperature, changes to race programing should be
made and stringent management procedures be implemented
for greyhounds participating in races or trials. Further research
is required to investigate environmental eects on greyhounds
racing in tropical climates.
JM was responsible for conception and design of the work, the
acquisition, analysis and interpretation of data, draing and
revising, and gave nal approval for it to be published. GH was
responsible for help in interpretation of data and revising, and
gave nal approval for it to be published. SH assisted in the
conception and design of the work, the acquisition, analysis
and interpretation of data, draing and revising, and gave nal
approval for it to be published. All authors agree to be accountable
for all aspects of the work in ensuring that questions related to
the accuracy or integrity of any part of the work are appropriately
investigated and resolved.
e authors would like to acknowledge the assistance of the rac-
ing tracks in permitting the study to be performed, and all of the
greyhound owners and trainers who agreed for their greyhounds
to be included in the study.
Financial support for this PhD project was provided by
Greyhound Racing South Australia and the Austra lian Greyhound
Veterinarians Special Interest Group of the Australian Greyhound
Veterinary Association.
McNicholl et al.
Body Temperature in Racing Greyhounds
Frontiers in Veterinary Science | June 2016 | Volume 3 | Article 53
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Conict of Interest Statement: Funding for this study was provided by Greyhound
Racing South Australia and JM is employed as a racetrack veterinarian for grey-
hound races in South Australia. e authors believe that neither of these perceived
conicts inuenced the design, analysis and interpretation of the data presented.
Copyright © 2016 McNicholl, Howarth and Hazel. is is an open-access article
distributed under the terms of the Creative Commons Attribution License (CCBY).
e use, distribution or reproduction in other forums is permitted, provided the
original author(s) or licensor are credited and that the original publication in
this journal is cited, in accordance with accepted academic practice. No use,
distribution or reproduction is permitted which does not comply with these terms.
... Heat regulation problems are reported to affect around a third of brachycephalic dogs [17] and obesity has been reported as a significant risk factor for death in dogs presenting with HRI [18]. Reflecting the male predisposition to exertional HRI in humans, male dogs develop a significantly higher body temperature than females during intense exercise [19,20]. Both dogs trained for military work (e.g., Belgian Malinois) and active playful dogs (e.g., Golden Retriever and Labrador Retriever) have been reported to be at increased risk of exertional HRI [18], however, that study included only patients referred for specialist care and therefore may not represent the wider canine population. ...
... These findings mirror the human risk factors of exertional HRI, with young male athletes and labourers most likely to be affected [45]. Entire female dogs could have reduced odds for exertional HRI due to their relatively lower bodyweights compared to male and neutered animals [19], or, it could reflect reduced exercise levels during reproductive periods such as pregnancy and lactation. Dogs at or above the mean adult bodyweight for their breed/sex showed an increased risk of exertional HRI compared to dogs below the mean bodyweight, and all dogs weighing 10 kg or over had increased odds of exertional HRI compared to dogs weighing under 10 kg. ...
... Small breeds of dog are reported to have decreased risk of HRI [18], dogs with greater body mass have been reported to develop higher post exercise body temperatures [19]. ...
Full-text available
Heat-related illness will affect increasing numbers of dogs as global temperatures rise unless effective mitigation strategies are implemented. This study aimed to identify the key triggers of heat-related illness in dogs and investigate canine risk factors for the most common triggers in UK dogs. Using the VetCompassTM programme, de-identified electronic patient records of 905,543 dogs under primary veterinary care in 2016 were reviewed to identify 1259 heat-related illness events from 1222 dogs. Exertional heat-related illness was the predominant trigger (74.2% of events), followed by environmental (12.9%) and vehicular confinement (5.2%). Canine and human risk factors appear similar; young male dogs had greater odds of exertional heat-related illness, older dogs and dogs with respiratory compromise had the greatest odds of environmental heat-related illness. Brachycephalic dogs had greater odds of all three types of heat-related illness compared with mesocephalic dogs. The odds of death following vehicular heat-related illness (OR 1.47, p = 0.492) was similar to that of exertional heat-related illness. In the UK, exertional heat-related illness affects more dogs, and kills more dogs, than confinement in a hot vehicle. Campaigns to raise public awareness about heat-related illness in dogs need to highlight that dogs don’t die just in hot cars.
... This has threatened the ongoing public acceptance of the industry's standard practices and its social license to operate. The science of greyhound welfare is an area of growing interest, with a focus on stress associated with the race and race meet protocols [1][2][3][4]. Stress can compromise an animal's optimal state of homeostasis and wellbeing [5]. Shifts in the animal's ability to cope may manifest as a behavioural, physiological or psychological response to an external or internal stimulus [5]. ...
... The effects of stressors on affective state vary in their valence (from pleasant to unpleasant) and with the animal's current level of arousal (from deactivated to activated). There is evidence that greyhounds exhibit signs of physiological stress and arousal during a race meet [1][2][3], with arousal ranging from calm to alert, or excited [7,8]. Best practice in housing and managing greyhounds during a race meet should include optimising arousal and affective state at the time of maximal exertion, as well as the early detection and mitigation of stress. ...
... Along with stressors associated with the race meet, there are other environmental and biological factors that could influence the IRT measurements and must be considered when assessing stress and arousal [32,33]. Ambient temperature and humidity could be sources of stress during a race, as these factors can compromise an animal's ability to thermoregulate [2,34,35]. A previous greyhound study found that rectal temperature (RT) increased during high ambient temperatures [2]. ...
Full-text available
Infrared thermography (IRT) can be used to identify stressors associated with greyhound racing procedures. However, factors unrelated to stress may influence measurements. Validation of an eye side (right or left) and a reference point on the eye is required if IRT is to be standardised for industry use. Infrared images of greyhound heads (n = 465) were taken pre-racing and post-racing at three racetracks. Average temperature was recorded at seven different locations on each eye. A multivariate analysis model determined how several factors influenced eye temperature (ET) pre-racing and post-racing. As expected, ET increased after racing, which may be attributed to physical exertion, stress and arousal. The right eye and lacrimal caruncle had the highest sensitivity to temperature changes and could be considered reference points for future studies. Additionally, dogs that raced later had higher ET, and Richmond racetrack had the lowest pre-race ET, but the highest post-race ET. This may suggest that arousal increases as the race meet progresses and certain track attributes could increase stress. Furthermore, ET increased as humidity increased, and higher post-race ET was associated with light-coloured, young and low-performing dogs. Environmental and biological factors need to be considered if IRT is to become accurate in the detection of canine stress and monitoring of greyhound welfare.
... Such an increase in skin temperature potentially changes the dynamics of heat transfer, resulting in decreased heat loss and possibly a heat gain (Otani et al., 2021). Animals with darker coloured hair coats may also be more susceptible to radiative heat gains than those with lighter colours (McNicholl et al., 2016;Walsberg et al., 1978). ...
... Since that time the WBGT has received widespread acceptance, been used during military, occupational, industrial and sporting activities and incorporated into heat policy recommendations by many high-profile human sporting organisations (Armstrong et al., 2017;Racinais et al., 2015). It has also been used for equestrian competitions (Jeffcott & Kohn, 1999;Jeffcott et al., 2009;Schroter et al., 1996) and forms part of heat policy guidelines for Thoroughbred, Standardbred and greyhound racing worldwide (McNicholl et al., 2016). The WBGT is an empirical index based on three measurements, the dry bulb temperature, the natural wetbulb temperature and the black-globe temperature. ...
Full-text available
A simple epidemiological model of disease causation is proposed for exertional heat illness (EHI) in Thoroughbred racehorses. The agent of disease causation that must be present for the condition to occur is strenuous exercise, producing substantial quantities of metabolic heat. This is stored during racing but must be dissipated rapidly in the post‐race period to prevent core body temperature rising to a critical level and causing the clinical manifestations of EHI. Environmental factors are next in the epidemiological triad, and it is a common misconception that these are the direct cause of EHI. In fact, environmental conditions enable EHI by either diminishing the evaporative capacity of the environment or promoting internal heat gain. This article deals with the specific effects of the four thermal elements, separately and in combination, on individual thermo‐effector mechanisms. The final component in the epidemiological triad is individual host factors. A critical premise of epidemiology is that conditions such as EHI may not occur randomly in a population but may be more likely to occur in some individuals due to the presence of certain factors that predispose them to the condition. For the purpose of assessing risk, it is not feasible to examine the balance between metabolic heat production and the intrinsic and extrinsic factors, which collectively determine each individual's heat stress response. Therefore, the measurement of environmental factors remains the only practical way of obtaining a credible risk assessment for EHI, so that effective countermeasures can be instigated and the welfare of our racehorses ensured.
... In our study, we observed that even in dogs running in the thermoneutral zone with temperatures below 20 • C, rectal temperature can rise up to 41.7 • C ( Table 1). The increase in rectal temperature in participating dogs ranged from 0.1 to 3.0 • C, which is similar to results reported by McNicholl and colleagues (83) and Carter and Hall (7) where the mean increase in body temperature was 2.1 • C (rectal temperature) and 1.8 • C (tympanic membrane temperature), respectively, and was significantly related to ambient temperature. Similarly, as in the study by Carter and Hall (7), all dogs in our study returned to a normal body temperature soon after the cessation of exercise, which suggests that appropriate cooling mechanisms preventing prolonged hyperthermia are likely in place in these dogs. ...
Full-text available
Canicross is a sport discipline that connects human and canine athletes in running. Changes in physiological, hematological, and biochemical parameters, and exercise-induced oxidative stress have not been thoroughly characterized in canicross dogs. The aim of our study was the assessment of the health status of trained canicross dogs that were subjected to two acute bouts of exercise with their owners during the training season. Health status was assessed by measuring the rectal temperature, hematological and biochemical parameters, as well as blood oxidative stress parameters (plasma malondialdehyde, lipid peroxidation marker; whole blood glutathione peroxidase and erythrocyte superoxide dismutase1, antioxidant enzymes) before and during a two-day canicross training session and after a 24-h rest period. Seven trained canicross dogs (three females/four males) aged 12–120 months were included in the study. Blood samples were collected before and immediately after the first acute bout of exercise (day 1), after the second acute bout of exercise (day 2), and after 24 h of rest (day 3). Rectal temperature was measured at the same time as blood sample collection. The majority of hematological and biochemical parameters remained within reference ranges at all sampling times. Rectal temperature was significantly higher after training on days 1 and 2 compared to resting temperature on day 3. Hematological parameters did not change significantly; however, there were significant differences in urea, creatinine, creatine kinase, and triglycerides between specific sampling times. Despite significant changes, these biochemical parameters remained within reference ranges. Significant changes in biochemical parameters seem to reflect the dogs' physiological response to each acute bout of exercise, considering all biochemical parameters and rectal temperature returned to pre-exercise values after a 24-h rest period (day 3). No significant differences in oxidative stress parameters were found between any sampling times. Relatively high erythrocyte superoxide dismutase1 activity at all sampling times may indicate that the canicross dogs are adapted to training by an increased expression of antioxidant enzymes. Based on our results, we can conclude that the trained canicross dogs included in our study were healthy, in good physical condition, and fit for the two acute bouts of field exercise.
... This suggests there may be a mismatch between the owner's perception of their dog's ability to exercise in hot weather and the dog's actual thermoregulatory ability. Conversely, male neutered dogs were considered to have higher summer CAS compared to female entire dogs, which reflects the findings of Hall et al. [2], that male neutered dogs had the greatest odds for exertional HRI, and studies report higher post-exercise body temperatures in male dogs compared to females [36,37]. Dogs active for 120 min or more each day were considered to have lower summer CAS compared to dogs completing less than 10 min per day. ...
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Climate change is leading to more instances of seasonal weather variation. Studies have explored the impact of adverse winter weather on dog walking, but the impact on the dog’s overall activity levels have not been previously considered. This study explored dog owner perceptions of the effects of both summer and winter weather on their dog’s activity levels. An international online survey recruited 3153 respondents between May and December 2018, to explore the impact of summer and winter weather conditions on baseline activity levels. Owners reported their dogs were more impacted by cold (48.2% less likely to exercise their dog in the cold) and ice (64.0% less likely), than rain (25.3% were less likely). In hot weather, over 80% of owners reported reduced exercise duration and vigour for their dogs. Carrying water or walking near water to facilitate activity in the summer was the most popular mitigation strategy (90.8%). Participation in dog sports appeared to reduce the impact of winter weather on canine activity and increase owner awareness of cooling strategies to facilitate summer activity. Strategies to promote safe activity participation are needed to maintain canine activity levels amidst rising global temperatures, including better understanding of cooling strategies for exercising dogs.
... Siettou et al. (2014) did find that >8 year old dogs marginally more likely to be adopted than 5-7 years (adult), suggesting adopter's desire to 'rescue' older dogs as a reason for this finding. The higher number of Greyhounds in the subadult age category is likely to relate to the retirement age from racing (McNicholl, Howarth, & Hazel, 2016). While few age to breed associations were evident, this could be related to the smaller sample sizes in each age category. ...
Rescue centers remain a common means of rehoming a dog. There is a paucity of research into the composition of rescue center populations and its potential reflection of increased popularity of brachycephalic breeds. The study investigated changes in rescue center demographics from 2015 to 2018, compared to the wider dog population. Dogs on 16 rehoming centers’ websites were recorded weekly from June 2015 for 8 weeks and replicated from June 2018. Data were collected on 1793 dogs across the centers. Over 50% of which were classified as purebred in both years. Over 80% of the dogs were categorized into 24 breeds or breed crosses. Dogs categorized as brachycephalic increased from 24 (2.76%) in 2015 to 48 (5.19%) in 2018. Subadult dogs (3–4 years) were most prevalent in both years. While sex, breed type, and age of the rehoming center population has remained relatively stable, breeds are changing. Whilst low, brachycephalic numbers doubled in 3 years, mirroring their rising popularity within the UK, impacting on rehoming centres and prospective new owners with additional costs of brachycephalic obstructive airway syndrome surgery.
Although dark coat color in dogs has been theorized as a risk factor for heat injury, there is little evidence in the scientific literature to support that position. We utilized 16 non-conditioned Labradors (8 black and 8 yellow) in a three-phase test to examine effects of coat color on thermal status of the dog. Rectal, gastrointestinal (GI), and surface temperature using infrared thermography measured at the eye and abdomen, were measured along with respiration rate measured in breaths per minute (bpm), collected at three time points. Phase 1 (Baseline) – 30 minutes of crate rest in a climate-controlled room; Phase 2 (Walking in Sunlight) - 30-minute walk in an outdoor environment on a sunny day; and Phase 3 (Cooling) – 15 minutes of crate rest in climate-controlled room to determine post-exposure recovery temperatures. No effect of coat color was measured for rectal, gastrointestinal, surface temperature, or respiration rate (P > 0.05) in dogs following their 30-minute walk in sunlight. All temperatures measured increased similarly (rectal 1.86°C and 1.80°C; GI 1.92°C and 1.95°C; eye 2.8°C and 1.92°C; abdomen 2.91°C and 2.39°C) in black and yellow dogs respectively, following 30 in Sunlight (P > 0.05). Additionally, temperatures decreased in a similar fashion for both coat colors (rectal 0.84°C and 0.88°C; GI 1.48°C and 1.32°C; eye 1.49°C and 1.70°C; abdominal 1.75°C and 1.5°C) in black and yellow dogs respectively (P > 0.05) during Cooling. Respiration rate increased similarly for both coat colors, (147.2 bpm and 143.7 bpm for black and yellow respectively) when Baseline values were compared to Sunlight values and decreased similarly (28.8 bpm black; 60.2 bpm yellow after Cooling phase (P > 0.05). These novel data reveal a surprising lack of effect for black vs. yellow coat color on body temperature as measured by standard rectal thermometer, gastrointestinal thermistor, or infrared thermography in a population of Labrador retrievers.
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Core body temperature is indispensable in the assessment of the health status, as well as diagnosis and management of febrile conditions in patients. However, taking temperature in veterinary practice using conventional rectal thermometry could be challenging as most animals like horses often resent it. In this report, the reliability and accuracy of non-contact infrared thermometry in measuring temperature in horses is evaluated. Body surface infrared temperature readings of 40 horses were measured from three different sites (forehead, shoulder point, and anal verge regions) and compared with rectal thermometry as gold standard, the mean temperature differences, spearman’s correlation and reliability coefficients were calculated for each measurement site. Bland-Altman plot was used to assess the agreement and systematic differences between the non-contact infrared and rectal thermometry. All the analyses were evaluated at α0.05. The body surface temperatures were slightly lower and correlate poorly with rectal temperature (p>0.05). The Bland-Altman analysis showed low mean bias ± SD between infrared and rectal thermometry as forehead (1.06 ± 0.48℃), shoulder point (0.77 ± 0.48℃), and anal verge (0.32 ± 0.63℃); and high reliability with clinical potentials (Intraclass correlation and Cronbach's Alpha coefficients (r) ≥ 0.98). Based on this data, with the high consistency and agreement, as well as the low mean biases below 1oC, the non-contact infrared thermometry of the anal verge and shoulder point demonstrated the greatest clinical potentials as an alternative to rectal thermometry in horses.
The study aimed at comparing variations in body temperature values recorded using rectal digital, infrared, and mercury-in-glass thermometers in donkeys during the hot-dry season, prevailing under tropical savannah conditions. Thirty donkeys that served as subjects were divided into three groups of adults, yearlings, and foals. Values of the body temperature of each donkey were recorded bihourly, starting from 06:00 h till 18:00 h, by digital (5-cm depth of insertion), mercury-in-glass (3 cm depth), and infrared thermometers. The values obtained by each type of the thermometer were compared with those recorded using a 15-cm digital probe (Model HI935007, Hanna Instruments, range −50.0 to 150.0°C; accuracy ± 0.2°C) which served as the gold standard. Dry-bulb temperature (34.00 ± 0.50°C), temperature-humidity index (79.65 ± 0.15), and wet-bulb globe temperature (28.00 ± 0.50) index peaked at 14:00 h. The mean body temperatures for rectal probe, digital, mercury-in-glass, and infrared thermometers were 38.35 ± 0.11°C, 37.24 ± 0.04°C, 36.76 ± 0.06°C, and 36.92 ± 0.07°C, respectively. In comparison to the rectal probe, the mean bias for digital (−1.11 ± 0.05°C), mercury-in-glass (−1.59 ± 0.07°C), and infrared thermometers (−1.38 ± 0.07°C) was large. The Passing-Bablok regression plot demonstrated significant deviation from linearity (p < 0.01) when digital, infrared, and mercury-in-glass thermometers were compared to the rectal probe. The area under the curve (AUC) for digital (AUC: 0.7005 ± 0.01 [95%: 0.6853 – 0.7310], infrared (AUC: 0.6711 ± 0.01 [95%: 0.6322 – 0.7100], and mercury-in-glass (AUC: 0.6321 ± 0.01 [95%: 0.6001 – 0.7873] thermometers showed poor accuracy with low sensitivity. In conclusion, the use of digital, mercury-in-glass, and infrared thermometers in recording body temperature in donkeys during the hot-dry season underestimated the values. Their use in measuring body temperature may result in wrong diagnosis, and compromise the control of hyperthermia and diseases associated with thermoregulatory impairments in donkeys.
Specific situations and legal requirements in some countries require dogs to wear a muzzle on a regular basis. Ongoing discussions within different national authorities are trying to balance the safety of the public against welfare of dogs when being walked. However, detailed information on ideal type of muzzle, muzzle fit, introduction techniques to wearing a muzzle and effects of muzzle use on the physical condition and behavior on dogs is very limited. Hence, this study collected data via an online survey on frequency and circumstances of muzzle use and observed effects on dogs when wearing a muzzle by also incorporating training techniques and muzzle type used. Of 1,862 respondents, only 21.6% indicated their dog never wears a muzzle (average age: 5.8 ± 3.6 years). Around half of the owners stated that their dog wears a muzzle only when mandatory by legislation (47.8%) and/or when necessary to prevent a bite (47.5%). Public transport and crowded public places were situations, where muzzles were employed most often. While basket type muzzles (made of BioThane, plastic, wire) were used most often, only 71.3% reported a fit not clearly impairing dog welfare. Muzzle introduction technique (habituation, short training, intense training, no preparation) used, significantly impacted on adverse behaviors observed when wearing a muzzle for the first time, and on ongoing behavior when muzzled such as trying to pull the muzzle off, rubbing the nose against objects or freezing behavior. Using food during muzzle training significantly decreased levels of passive avoidance during fastening and increased the likelihood of dogs actively putting their nose into the muzzle. Negative effects on behavior when wearing a muzzle were reported by 19.6% of owners and labelled with the terms ‘insecure, apathetic, dull, passive, distressed, anxious, unwell, agitated, nervous, tense, sad or miserable’. Changes in dog behavior were perceived as an advantage with respect to inability to access food (41.9%) and when used for veterinary visits (30.9%). Observed physical damage of either fur or skin, effects on thermoregulation, the ocular or gastrointestinal tract were reported by 161 (12.9%) owners. The results of this survey indicate a need to educate dog owners on muzzle fit and training protocols to reduce negative effects on dog welfare. In addition, potential alterations in intraspecies communication, other social behaviors and welfare need to be explored in more detail.
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In 1980, 1700 people died during a prolonged heat wave in a region under-prepared for heat illness prevention. Dramatically underreported, heat-related pathology contributes to significant morbidity as well as occasional mortality in athletic, elderly, paediatric and disabled populations. Among US high school athletes, heat illness is the third leading cause of death. Significant risk factors for heat illness include dehydration, hot and humid climate, obesity, low physical fitness, lack of acclimatisation, previous history of heat stroke, sleep deprivation, medications (especially diuretics or antidepressants), sweat gland dysfunction, and upper respiratory or gastrointestinal illness. Many of these risk factors can be addressed with education and awareness of patients at risk. Dehydration, with fluid loss occasionally as high as 6–10% of bodyweight, appears to be one of the most common risk factors for heat illness in patients exercising in the heat. Core body temperature has been shown to rise an additional 0.15–0.2°C for every 1% of bodyweight lost to dehydration during exercise. Identifying athletes at risk, limiting environmental exposure, and monitoring closely for signs and symptoms are all important components of preventing heat illness. However, monitoring hydration status and early intervention may be the most important factors in preventing severe heat illness.
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Severe cases of environmental or exertional heat stress can lead to varying degrees of organ dysfunction. To understand heat-injury progression and develop efficient management and mitigation strategies, it is critical to determine the thermal response in susceptible organs under different heat-stress conditions. To this end, we used our previously published virtual rat, which is capable of computing the spatiotemporal temperature distribution in the animal, and extended it to simulate various heat-stress scenarios, including 1) different environmental conditions, 2) exertional heat stress, 3) circadian rhythm effect on the thermal response, and 4) whole-body cooling. Our predictions were consistent with published in vivo temperature measurements for all cases, validating our simulations. We observed a differential thermal response in the organs, with the liver experiencing the highest temperatures for all environmental and exertional heat-stress cases. For every 3°C rise in the external temperature from 40 to 46°C, core and organ temperatures increased by ~0.8°C. Core temperatures increased by 2.6 and 4.1°C for increases in exercise intensity from rest to 75% and 100% of maximal O2 consumption, respectively. We also found differences as large as 0.8°C in organ temperatures for the same heat stress induced at different times during the day. Even after whole-body cooling at a relatively low external temperature (1°C for 20 min), average organ temperatures were still elevated by 2.3 to 2.5°C compared with normothermia. These results can be used to optimize experimental protocol designs, reduce the amount of animal experimentation, and design and test improved heat-stress prevention and management strategies.
Classically, the concept of energy balance has been presented by a simple equation: $$ {\bf{Energy}}\,{\bf{balance}}\,{\bf{ = }}\,{\bf{energy}}\,{\bf{in}}\,{\bf{ - }}\,{\bf{energy}}\,{\bf{out}}
Heatstroke is a rapidly progressive life-threatening emergency resulting from direct thermal injury to cardiovascular, gastrointestinal, renal, hepatic, endothelial, musculoskeletal, and central nervous tissues. Thermal injury to cells causes generalized cellular necrosis through denaturization of proteins, inactivation of enzyme systems, destruction of cell membrane lipids, and alteration of mitochondrial function. Heatstroke is precipitated by the collective inability of the body to maintain normal thermoregulation through proper cooling and heat dissipation mechanisms, Classic (or nonexertional) heatstroke most commonly develops when dogs are confined in an overheated enclosure. Exertional heatstroke is associated with muscular activity and is most common in dogs with such predispositions as obesity, laryngeal paralysis, and brachycephalic conformation. Common complications of heatstroke include oliguric renal failure, disseminated intravascular coagulation, cardiac arrhythmias, septic shock, and seizures.
Heatstroke is an acute, life-threatening emergency with a complex pathophysiology - the key clinical features of which Include metabolic acidosis, oliguric renal failure, coagulation abnormalities, and neurologic disturbances. Physical examination is marked by excessive panting, hyperemia, hypersalivation, tachycardia, and various neurologic signs. Common laboratory changes associated with heatstroke are hemoconcentration, elevated liver enzymes, electrolyte changes, prolonged clotting times, azotemia, and hypoglycemia. Rapid cooling of the core body and support of vital organs are essential factors in the management of heatstroke and prevention of further secondary sequelae. Prognosis worsens if severe neurologic signs develop and persist throughout the course of treatment. Owners of heatstroke animals can decrease mortality if the animal is cooled before being transported to the veterinarian. Prevention of heatstroke is achieved primarily by educating owners about proper acclimatization times, exercising during cooler periods of the day, and providing adequate shade and cool water for dogs confined outdoors.
The extreme physical endurance demands and varied environmental settings of marathon footraces have provided a unique opportunity to study the limits of human thermoregulation for more than a century. High post-race rectal temperatures (Tre) are commonly and consistently documented in marathon runners, yet a clear divergence of thought surrounds the cause for this observation. A close examination of the literature reveals that this phenomenon is commonly attributed to either biological (dehydration, metabolic rate, gender) or environmental factors. Marathon climatic conditions vary as much as their course topography and can change considerably from year to year and even from start to finish in the same race. The fact that climate can significantly limit temperature regulation and performance is evident from the direct relationship between heat casualties and Wet Bulb Globe Temperature (WBGT), as well as the inverse relationship between record setting race performances and ambient temperatures. However, the usual range of compensable racing environments actually appears to play more of an indirect role in predicting Tre by acting to modulate heat loss and fluid balance. The importance of fluid balance in thermoregulation is well established. Dehydration-mediated perturbations in blood volume and blood flow can compromise exercise heat loss and increase thermal strain. Although progressive dehydration reduces heat dissipation and increases Tre during exercise, the loss of plasma volume contributing to this effect is not always observed for prolonged running and may therefore complicate the predictive influence of dehydration on Tre for marathon running. Metabolic heat production consequent to muscle contraction creates an internal heat load proportional to exercise intensity. The correlation between running speed and Tre, especially over the final stages of a marathon event, is often significant but fails to reliably explain more than a fraction of the variability in post-marathon Tre. Additionally, the submaximal exercise intensities observed throughout 42km races suggest the need for other synergistic factors or circumstances in explaining this occurrence There is a paucity of research on women marathon runners. Some biological determinants of exercise thermoregulation, including body mass, surface area-to mass ratio, sweat rate, and menstrual cycle phase are gender-discrete variables with the potential to alter the exercise-thermoregulatory response to different environments, fluid intake, and exercise metabolism. However, these gender differences appear to be more quantitative than qualitative for most marathon road racing environments.
Exertional heat-related illness (EHRI) is comprised of several states that afflict physically active persons when exercising during conditions of high environmental heat stress. Certain forms of EHRI may become life threatening if not treated. Exertional heat stroke (EHS), characterized by a core body temperature of >40 ° C and mental status changes, is the most severe form of EHRI. EHS must be treated immediately with rapid body cooling to reduce morbidity and mortality. Many EHRI cases are preventable by following heat acclimatization guidelines, modifying sports and exercise sessions during conditions of high environmental heat stress, maintaining adequate hydration, avoiding exertion in the heat when ill, and by educating sports medicine personnel, coaches, parents, and athletes on the early recognition and prevention of EHRI. Heat exhaustion, exercise-associated collapse, exercise-associated muscle cramps, exercise-associated hyponatremia, and exertional rhabdomyolysis are also described.