This article was downloaded by: [Dr Kenneth Shapiro]
On: 09 June 2015, At: 06:47
Publisher: Routledge
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Journal of Applied Animal
Welfare Science
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/haaw20
Measuring the Heat Loss in
Horses in Different Seasons by
Infrared Thermography
Elena Autio , Riitta Neste , Sanna Airaksinen &
Minna-Liisa Heiskanen
Published online: 04 Jun 2010.
To cite this article: Elena Autio , Riitta Neste , Sanna Airaksinen & Minna-Liisa
Heiskanen (2006) Measuring the Heat Loss in Horses in Different Seasons by Infrared
Thermography, Journal of Applied Animal Welfare Science, 9:3, 211-221, DOI:
10.1207/s15327604jaws0903_3
To link to this article: http://dx.doi.org/10.1207/s15327604jaws0903_3
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or
indirectly in connection with, in relation to or arising out of the use of the
Content.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions
JOURNAL OF APPLIED ANIMAL WELFARE SCIENCE, 9(3), 211–221
Copyright © 2006, Lawrence Erlbaum Associates, Inc.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
Measuring the Heat Loss in Horses
in Different Seasons by Infrared
Thermography
Elena Autio, Riitta Neste, Sanna Airaksinen,
and Minna-Liisa Heiskanen
Equine Information Centre
University of Kuopio
It is necessary to consider breed and cold tolerance in the housing and caring of
horses. This study demonstrates differences in heat loss between horse types at low
temperatures and examines rate of loss in different types during different seasons.
Eighteen horses participated. Groups by type were light (L), warmblood (W),
coldblood (C), and pony (P). A camera filmed thermographic images at 15° C, 2° C
(all types), –8° C (L, W, C), and –12° C (P). The study calculated loss from the neck,
trunk, and inner surfaces of front and hind legs. Loss was similar in all types at 15° C.
L, W, and C dissipated more heat at 2° C than at 15° C (p < .001) and from neck and
trunk at –8° C than at 2° C (p < .05). P dissipated heat similarly at 2° C and –12° C. At
2° C, loss was less from neck and trunk in C and P compared with L (p < .05). At –8° C,
loss in L and W was greater than in C (p < .05).
A horse’s breed, cold tolerance, plane of nutrition, and the importance of shelter
should be noted in the housing and care of horses in different seasons. Ambient
temperature, wind, and precipitation affect the rate of heat loss (MacCormack &
Bruce, 1991). Therefore, winter weather increases the maintenance energy need
of horses kept outside. The most important single climatic stressor is ambient
temperature (Cymbaluk & Christison, 1990), which varies between 30° C and
–30° C in northern Europe, depending on the season. Long cold periods (–20° C
to –30° C) may continue for weeks in winter. The temperature directly influCorrespondence should be sent to Elena Autio, Equine Information Centre, University of Kuopio,
P.O. Box 1627, FI–70211 Kuopio, Finland. Email: [email protected]
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
212
AUTIO, NESTE, AIRAKSINEN, HEISKANEN
ences the metabolic rate of animals and indirectly influences their health and
welfare (Clark & McArthur, 1994). There are limited published data on the cold
tolerance of different horse types. The differences between horse types have not
usually been taken into account in the construction design of stables, although it
is generally thought that coldblood horses are more cold tolerant than
warmblood horses (Bender, 1999).
The heat production and heat loss of horses have previously been studied by
measuring the level of metabolism using indirect calorimetry (Ousey, McArthur,
Murgatroyd, Stewart, & Rossdale, 1992) and a hygrometric tent (Morgan, 1997a,
1997b; Morgan, Ehrlemark, & Sällvik, 1997). Respiratory heat loss has been studied by measuring temperature differences across the pulmonary circulation
(Hodgson et al., 1993). Kauppinen (2000) examined heat loss in dairy calves and
Korhonen and Harri (1986) in farmed raccoon dogs by infrared thermography. The
surface temperature of different regions of a horse’s body has also been examined
using thermography (Holmes, Gaughan, Gorondy, Hogge, & Spire, 2003; Tunley
& Henson, 2004; Verschooten, Desmet, & Verbeeck, 1997); in addition, it is used
to a large extent in the diagnosis of muscle, tendon, joint, and hoof injuries (Eddy,
Van Hoogmoed, & Snyder, 2001; Lessiter, 1998; Turner, 2001).
The aim of this study was to provide information on the cold tolerance of different horse types during different seasons. The rate of heat loss was measured
from different body regions using infrared thermography. It was hypothesized
that there may be differences in the rate of heat loss between different horse
types at low temperatures. In addition, it was assumed that the light and
warmblood horse types would dissipate more heat than the coldblood and pony
types.
MATERIALS AND METHOD
Animals
The study was carried out between August 1998 and March 2000 in Kiuruvesi,
Finland (63°29' N, 26°38' E). Eighteen horses participated in the study. The
horses were divided into four groups according to horse type: light (L),
warmblood (W), coldblood (C), and pony (P) (Table 1). The same people were
not caregivers (owners) of the horses, but the horses were working similarly and
fed for moderate work scaled to body weight (Tuori et al., 1996). The mean age
of the horses was 9.5 years (SD = 4.8 years) at the beginning of the study. The
horses were housed in a stable and kept in a paddock 10 hr a day between September and May. In the summer, the horses were kept in a pasture for 24 hr a
day. Rugs were not used; thus, the horses were able to acclimatize to seasonal
environmental conditions.
MEASURING HEAT LOSS IN HORSES
213
TABLE 1
Characteristics of the Horse Types Used in the Study
Breed
n
Gender
Weighta
Body
Condition
Score
1. Light Type (L)
Standardbred
4
Gelding
458.5 ± 68.8
3.3 ± 0.5
2. Warmblood
type (W)
Danish
Warmblood
Polish
Warmblood
3
Gelding
604.0 ± 25.4
5.0 ± 1.6
1
Gelding
3. Coldblood type
(C)
Finnish horse
4
Gelding
547.5 ± 20.6
5.0 ± 1.2
4. Pony type (P)
Connemara
Pony
New Forest
Pony
2
1
1
2
Gelding
Mare
Gelding
Mare
323.3 ± 26.8
5.0 ± 1.7
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
Horse Type
Origin /Description
A light horse breed of
North American
originb
Warmblood breeds
were developed by
crossing draft
horses with light
horses.b
A light-heavy horse
breed originating
from Finland.c
Irelandb
Southern England
aGiven in kg. b Definition by Wagoner (1999). cSuomen Hippos, the national body of trotting and breeding in
Finland.
The body condition of the horses was evaluated using a scale of 1 to 9
(Henneke, Potter, Kreider, & Yeates, 1983) before the thermographic examination
(Table 1). The body condition of the horses did not change during the study. In addition, hair samples were taken from the midneck about 5 cm below the base of the
mane using a coat clipper (Oster Golden A5®, Oster Professional Products,
McMinnville, TN). The sample area was determined, and the samples were
oven-dried at 40° C for 12 hr and weighed. The hair weight per area unit was calculated. The following hair sample was taken from an area next to the previous sampling area. Care was taken in subsequent samplings not to overlap with the
previous sampling area.
Thermographic Examination
The thermographic examination was carried out in August (15° C) and October
(2° C) in 1998 with all the horse types; in March 1999 (–12° C) with type P; and
in March 2000 (–8° C) with types L, W, and C. The thermographic examination
of types L, W, and C failed in March 1999, which is why the examination was
repeated with the same horses 1 year later at the same time of the year. The temperatures given in parentheses are the temperatures in the riding arena at the
time of the thermographic examination.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
214
AUTIO, NESTE, AIRAKSINEN, HEISKANEN
The circumstances were standardized by taking the horses to a cold, indoor riding arena that protected them from wind, sun, and rain. The temperature in the riding arena was the same as the outside temperature (difference < 0.5° C), to which
the horses were acclimatized. The horses were paired and kept in small pens inside
the riding arena. The horses were fed in the morning at 6:00 and brought to the riding arena after feeding, 3 hr before the thermal examination. The recommended
period required for a horse to equilibrate fully to its environment prior to taking
thermographic images is between 39 and 60 min (Tunley & Henson, 2004). The
temperature in the arena was measured every 30 min during the 3 hr and was 14.7 ±
0.6° C in August, 2.0 ± 0.5° C in October, and –8.2 ± 0.2° C and –11.3 ± 0.6° C in
March. The horses were not fed during the examination.
Thermal images were taken with an Inframetrics 600 camera (FLIR Systems,
Inc., Portland, OR), which is a thermographic system with 256 × 200 pixels per
frame. The camera has a 15 × 20° field of view and is capable of distinguishing a
temperature difference of 0.1° C. A general view was taken from the nonmane side
of the horse at a distance of 8 m and the images of the legs at a distance of 1 m. The
rate of emissivity used was 0.95. A thermographic camera detects surface heat
emitted as infrared radiation and produces a picture that is a map of temperature
differences across the target (Dereniak & Boreman, 1996). In a cold environment,
heat is mainly dissipated as nonevaporative heat loss (McArthur, 1991). Heat loss
is expressed in watts per square meter (W/m2) of surface area of the animal
(MacCormack & Bruce, 1991). The images were analyzed at Satakunta Polytechnic in Pori, Finland.
The rate of heat loss (W/m2) was calculated from the neck (the area between the
ear, withers, elbow, and throatlatch), trunk (the area from the withers and the point
of the elbow to the buttock), and inner surfaces of the front and hind legs (the area
of the armpit or groin) using a Microsoft Excel® based computer program developed at Satakunta Polytechnic (Figure 1). The neck and trunk were chosen as measuring points for a practical reason: Heat loss from these areas can be reduced with
a rug. The front and hind legs were chosen to represent special regions of the body.
The program calculated the heat radiated from a particular area of the horse by the
calculation method derived from Stefan–Boltzmann’s Law (Dereniak & Boreman,
1996):
P = εσ(Ts4 – Ta4 )
P = emitted power (W / m 2 )
ε = emissivity 0.95
σ = Stefan–Boltzmann constant 5.67 × 10 –8Wm –2 K –4
Ts = surface temperature (K )
Ta = air temperature (K )
— = average of measuring points.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
MEASURING HEAT LOSS IN HORSES
215
FIGURE 1 A thermographic image of a standardbred horse (light horse type) at a temperature
of 2° C. The areas of the neck, trunk, front leg, and hind leg where the rate of heat loss was determined are outlined.
Statistical Analyses
The statistical analyses were made using nonparametric tests in SPSS 10.0 for
Windows. The effect of horse type and environmental temperature on heat loss
was tested using the Kruskal–Wallis and Mann–Whitney U tests. The differences in heat loss from the various body regions were tested using the Friedman
and Wilcoxon signed-rank tests. The differences in hair weight were tested using
the Kruskal–Wallis and Mann–Whitney U tests. Nonparametric statistical tests
were chosen because they are suitable for statistical analysis of data with a small
number of samples and an abnormal distribution.
RESULTS
Effect of Environmental Temperature on Heat Loss
The L, W, and C horse types dissipated more heat from the trunk, neck, front,
and hind legs at 2° C than at 15° C (p < .001; Table 2). Heat loss from the P type
was similar at 2° C and –12° C. In Type P, heat loss from the front and hind legs
was greater at –12° C than at 15° C (p < .05). There were no differences between the neck and trunk in Type P at 15° C and –12° C. The change in temperature from 2° C to –8° C increased heat loss from the trunk and neck in Types L,
TABLE 2
The Rates of Heat Loss in Light, Warmblood, and Coldblood Horse Types and Pony Type
From the Trunk, Neck, Front Leg, and Hind Leg at Different Temperatures
Horse Type
La,b
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
Body
Region
15° C
T
N
FL
HL
2° C
T
N
FL
HL
–8° C
T
N
FL
HL
–12° C
T
N
FL
HL
Wa,b
M
SD
39.5
43.5
28.0
19.0
2.4
1.3
14.1
14.2
77.5d
83.0d
113.5g
134.0f
96.5h
108.0h
123.0i
158.5i
M
Ca,b
SD
M
37.3
38.8
30.8
32.5
13.3
15.7
5.0
12.0
40.5
44.8
25.8
23.5
1.3
4.3
8.1
11.4
70.8
76.5e
100.8g
102.8
12.1
12.1
8.5
5.4
8.3
10.0
12.4
20.0
97.0h
112.0h
101.5
142.2i
22.9
22.3
16.8
16.9
Pc
SD
M
SD
13.1
14.2
3.3
14.2
38.3
43.3
34.8
28.3
9.8
9.9
19.6
3.7
55.8
62.0
88.0g
105.0
5.0
5.0
18.0
8.7
51.7
58.2
66.8
89.3
11.1
14.0
5.8
15.2
68.2
81.7
90.2
111.6
7.9
11.8
6.8
16.6
48.7
58.8
62.2
97.5
5.9
8.7
15.6
40.2
Note. Light: n = 4; warmblood: n = 4; coldblood: n = 4; pony: n = 6. Heat loss measured in w/m2.
Asymptotic significance (two-tailed); Mann–Whitney U test. L = light; W = warmblood; C = coldblood;
P = pony; T = trunk; N = neck; FL = front leg; HL = hind leg.
aDifference in heat loss from T, N, FL, and HL in horse type between 15° C and 2° C (p < .001).
bDifference in heat loss from T and N in horse type between 2° C and –8° C (p < .05). cDifference in heat
loss from FL and HL in horse type between 15° C and –12° C (p < .05). dDifference in heat loss from
body region when compared with Types C and P at 2° C (p < .05). eDifference in heat loss from body
region when compared with Type C at 2° C (p < .05). fDifference in heat loss from body region when
compared with Types W, C, and P at 2° C (p < .05). gDifference in heat loss from body region when
compared with Type P at 2° C (p < .05). hDifference in heat loss from body region when compared with
Type C at –8° C (p < .05). iDifference in heat loss from body region when compared with Type C at –8° C
(p < .01).
216
217
MEASURING HEAT LOSS IN HORSES
W, and C (p < .05). That change in temperature did not influence the rate of heat
loss from the front and hind legs.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
Effect of Horse Type on Heat Loss
There were no differences between the horse types in the rate of heat loss from
different regions at 15° C (Table 2). Type L dissipated more heat from the trunk
and neck than Types C and P at 2° C (p < .05). Type W also dissipated more
heat from the neck than Type C at 2° C (p < .05). Type L lost more heat from
the hind legs than Types W, C, and P at 2° C (p < .05). Type P dissipated less
heat from the front legs than Types L, W, and C at 2° C (p < .05).
Type L dissipated more heat from the trunk, neck (p < .05), and front and hind
legs (p < .01) than Type C at –8° C (Table 2). Type W lost more heat from the
trunk, neck (p < .05), and hind legs (p < .01) than Type C at –8° C. There were no
differences in heat loss between Types L and W at –8° C.
Hair Weight
Hair weight increased in all the horse types between August and March (p <
.001; Table 3). Type L had less hair than types W, C, and P in August and October (p < .05). Types W and C also had less hair than type P in October (p < .05).
The hair weight of Types L and W was lower than that of types C and P in
March (p < .05).
TABLE 3
Hair Weight of Light, Warmblood, and Coldblood Horse Types and Pony Type From the
Neck in August, October, March, and April
Horse Type
L
Month
Augusta
October
Marchd
April
W
C
P
M
SD
M
SD
M
SD
M
SD
2.4b
6.5b
16.1c
8.0
1.3
0.7
4.3
5.0
8.2
11.3c
15.6e
8.7f
3.2
5.2
3.0
2.0
9.8
16.5c
42.0
13.2
5.2
4.8
8.0
2.0
9.1
33.3
36.9
15.4
2.2
5.7
13.3
2.0
Note. Light (L): n = 4; warmblood (W): n = 4; coldblood (C): n = 4; pony (P): n = 6. Dry weight
measured in mg/cm2. Asymptotic significance (two-tailed), Mann–Whitney U test.
aDifference in all horse types compared with March (p < .001). bDifference compared with Types W,
C, and P in August and October (p < .05). cDifference compared with Type P in October (p < .05).
dDifference in all horse types compared with April (p < .05). eDifference compared with Types C and P
in March (p < .05). fDifference compared with Type P in April (p < .05).
218
AUTIO, NESTE, AIRAKSINEN, HEISKANEN
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
DISCUSSION
The temperature of 15° C is within the thermoneutral zone of horses (Lewis,
1995). In this study, the rate of heat loss was lowest at 15° C. All the horse types
also dissipated heat equally from the neck, trunk, and between the legs at this
temperature. In a warm environment, the temperature difference between the
surface of the horse and the environment is small, which limits nonevaporative
heat loss (Morgan, 1997a). Heat loss occurs mainly by evaporation associated
with the loss of water vapor from the body surface and respiratory system (Clark
& McArthur, 1994).
The rate of nonevaporative heat loss increases almost linearly as the temperature decreases (Clark & McArthur, 1994). At a temperature of 2° C, differences in
heat loss started to occur. The L horse type dissipated more heat from the neck and
trunk than the C and P types. The body resistance affects the rate of heat loss
(Ousey et al., 1992). The total insulation between an animal’s body core and the
animal’s environment is provided by three thermal insulation layers acting in series: the peripheral body tissue, the coat, and the boundary layer of air (McArthur,
1991). The tissue resistance acts between the body core and skin surface (Ousey et
al., 1992). It depends on the thickness of the skin, the amount of subcutaneous fat,
and the peripheral blood flow. Reduction in peripheral blood flow in a cold environment decreases heat loss (Mogg & Pollitt, 1992). Subcutaneous fat is three
times more insulating than other tissues (Guyton, 1991). Thus, the lower body
condition score of Type L may have increased heat loss compared with the other
horse types.
The thermal insulation of the coat varies with the length and density of the hair
(Morgan, 1997b). In a cold environment, piloerection may also increase the insulating value of the coat because the amount of insulating air in the coat increases
(McArthur, 1991). Thus, it would have been interesting to measure the
piloerection of the hair at different temperatures. The lower hair coat weight of
horse type L versus C and P may have enhanced heat loss. In addition, Type W
horses have relatively thin skin compared with Type C horses (Talukdar, Calhoun,
& Stinson, 1972). It should be noted that the winter coat of the horses was still
growing in October, which may also explain the differences in the rates of heat loss
between the horse types.
The rate of heat loss of Types L, W, and C increased as the temperature dropped
from 2° C to –8° C. It should be noted that the –8° C examination of the horses was
carried out 1 year later, which dilutes the comparability of these results. The heat
loss in Type P did not increase greatly as the temperature dropped. The reason may
have been that these horses had a very thick winter coat in March when the thermal
images were taken at a temperature of –12° C. The thermal images at 2° C were
taken in October when the winter coat was still growing. A similar rate of heat loss
at 2° C and –12° C may indicate that the lower limit of the thermoneutral zone of
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
MEASURING HEAT LOSS IN HORSES
219
Type P was at least –12° C and not –8° C as Lewis (1995) stated. A temperature of
–12° C is not yet very cold for cold-adapted horses because they tolerate temperatures down to near –18° C in the absence of wind and moisture (Lewis, 1995).
However, for a confident conclusion, thermoneutrality should be studied further.
The size of the horse is an important factor in determining heat loss
(MacCormack & Bruce, 1991). The heat loss is directly proportional to the effective surface area involved in heat exchange. In addition, the mass of the animal has an influence. For example, the surface area in proportion to the body
weight is larger in calves than in adult animals, which enhances heat loss
(Pyykkönen, 1991). In this study, Type P differed from the other horse types;
they were the smallest in size and the only group with mares. In many cases,
however, Type P horses dissipated significantly less heat than the other horse
types. This may have been a consequence of the good body insulation (hair
weight) of the ponies.
Because of the different rates of heat loss from the different body regions, it is
important to measure heat loss at least from the neck and trunk. The inner surfaces
of the legs are special regions because of their thin skin and small surface area
compared with the neck and trunk. Therefore, these regions are not very representative in evaluating the general heat loss of horses. In the thermographic images
the head exhibited the hottest body temperature. Thus, it would be meaningful to
also measure the rate of heat loss from the head when estimating the
thermoregulation of a horse.
Infrared thermography usually provides a two-dimensional temperature field of
an object surface (Wolfe & Zissis, 1989). A profile was taken from the vertical side
of the horses and consequently there were not very steep curvatures in the body regions where the radiated heat was calculated. A curvature of a surface has an effect
on the precision of radiated temperature measurements when the angle of view exceeds 60° compared with the vertical view (Wolfe & Zissis, 1989). In this study,
this can be seen when examining the outer edges of the horse where the surface
temperature seems colder (Figure 1). These areas were not included in the calculations of radiated heat.
In northern Europe, long cold periods (–20° C to –30° C) may continue for
weeks in winter. Heat loss in horses should be studied further at even lower temperatures than those in this study. Another interesting factor is the effect of wind
and humidity on the rate of heat loss. A combination of cold and wind, especially
in wet weather, is very stressful for a horse; if the coat gets wet, its insulating capacity is lost (Lewis, 1995). It has been previously reported that a wind speed of 8
m/sec increases the heat flow from the coat two- to threefold compared with still
air (Morgan, 1994).
On the basis of this study, there are differences in the rate of heat loss at cold
temperatures between different horse types. In cold winter weather, L and W horse
types may benefit from extra feed or shelter more than C and P types. The rate of
220
AUTIO, NESTE, AIRAKSINEN, HEISKANEN
heat loss can be reduced with a rug, thereby lessening the need for extra energy in
cold weather (MacCormack & Bruce, 1991).
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
ACKNOWLEDGMENTS
We thank the State Provincial Office of Eastern Finland (European Social Fund)
and the Employment and Economic Development Centre of Northern Savo (European Agricultural Guidance and Guarantee Fund) for providing financial support for this study. We also thank the personnel of the Vocational Institute of
Ylä-Savo, P. Mäenpää, A. Lehmuskero, and T. Stjernberg from Infradex Oy for
their help.
REFERENCES
Bender, I. (1999). Praxishandbuch Pferdehaltung [The practical handbook of horse management].
Stuttgart, Germany: Franckh-Kosmos Verlags-GmbH.
Clark, J. A., & McArthur, A. J. (1994). Thermal exchanges. In C. M. Wathes & D. R. Charles (Eds.),
Livestock housing (pp. 97–122). Cambridge, England: CAB.
Cymbaluk, N. F., & Christison, G. I. (1990). Environmental effects on thermoregulation and nutrition of
horses. Veterinary Clinics of North America: Equine Practice, 6, 355–372.
Dereniak, E. L., & Boreman, G. D. (1996). Infrared detectors and systems. New York: Wiley.
Eddy, A. L., Van Hoogmoed, L. M., & Snyder, J. R. (2001). The role of thermography in the management of equine lameness. Veterinary Journal, 162, 172–181.
Guyton, A. C. (1991). Textbook of medical physiology. St. Louis, MO: Saunders.
Henneke, D. R., Potter, G. D., Kreider, J. L., & Yeates, B. F. (1983). Relationship between condition
score, physical measurements and body fat percentage in mares. Equine Veterinary Journal, 15,
371–372.
Hodgson, D. R., McCutcheon, L. J., Byrd, S. K., Brown, W. S., Bayly, W. M., Brengelmann, G. L., et al.
(1993). Dissipation of metabolic heat in the horse during exercise. Journal of Applied Physiology,
74, 1161–1170.
Holmes, L. C., Gaughan, E. M., Gorondy, D. A., Hogge, S., & Spire, M. F. (2003). The effect of
perineural anesthesia on infrared thermographic images of the forelimb digits of normal horses. The
Canadian Veterinary Journal, 44, 392–396.
Kauppinen, R. (2000). Acclimatization of dairy calves to a cold and variable microclimate (Doctoral
dissertation, University of Kuopio, Finland). Kuopio, Finland: Kuopio University Publications.
Korhonen, H., & Harri, M. (1986). Heat loss of farmed raccoon dogs and blue foxes as evaluated by infrared thermography and body cooling. Comparative Biochemistry and Physiology, 84A, 361–364.
Lessiter, F. (1998, July–August). Thermal imaging pinpoints ”hot” hoof concerns. American Farriers
Journal, pp. 53–59.
Lewis, L. D. (1995). Feeding and care of the horse. Philadelphia: Williams & Wilkins.
MacCormack, J. A. D., & Bruce, J. M. (1991). The horse in winter—Shelter and feeding. Farm Building
Progress, 105, 10–13.
McArthur, A. J. (1991). Metabolism of homeotherms in the cold and estimation of thermal insulation.
Journal of Thermal Biology, 16, 149–155.
Downloaded by [Dr Kenneth Shapiro] at 06:47 09 June 2015
MEASURING HEAT LOSS IN HORSES
221
Mogg, K. C., & Pollitt, C. C. (1992). Hoof and distal limb surface temperature in the normal pony under
constant and changing ambient temperatures. Equine Veterinary Journal, 24, 134–139.
Morgan, K. (1994). Fryser hästen på vintern? [Is the horse freezing in winter?] (Tech. Rep. No. 9).
Uppsala, Sweden: Swedish University of Agricultural Sciences.
Morgan, K. (1997a). Effects of short-term changes in ambient air temperature or altered insulation in
horses. Journal of Thermal Biology, 22, 187–194.
Morgan, K. (1997b). Thermal insulance of peripheral tissue and coat in sport horses. Journal of Thermal
Biology, 22, 169–175.
Morgan, K., Ehrlemark, A., & Sällvik, K. (1997). Dissipation of heat from standing horses exposed to
ambient temperatures between –3° C and 37° C. Journal of Thermal Biology, 22, 177–186.
Ousey, J. C., McArthur, A. J., Murgatroyd, P. R., Stewart, J. H., & Rossdale, P. D. (1992).
Thermoregulation and total body insulation in the neonatal foal. Journal of Thermal Biology, 17,
1–10.
Pyykkönen, M. (1991). Measuring the thermal environment of calves under sheltered winter conditions
(Research Rep. No. 65). Helsinki, Finland: University of Helsinki, Department of Agricultural
Technology.
Talukdar, A. M., Calhoun, M. L., & Stinson, A. W. (1972). Microscopic anatomy of the skin of the
horse. American Journal of Veterinary Research, 33, 2365–2390.
Tunley, B. V., & Henson, F. M. D. (2004). Reliability and repeatability of thermographic examination
and the normal thermographic image of the thoracolumbar region in the horse. Equine Veterinary
Journal, 36, 306–312.
Tuori, M., Kaustell, K., Valaja, J., Aimonen, E., Saarisalo, E., & Huhtanen, P. (1996). Rehutaulukot ja
ruokintasuositukset [Feed tables and nutrient requirements of ruminants, pigs, poultry, fur animals
and horses]. Helsinki, Finland: Yliopistopaino.
Turner, T. A. (2001). Diagnostic thermography. The Veterinary Clinics of North America: Equine Practice, 17, 95–113.
Verschooten, F., Desmet, P., & Verbeeck, J. (1997). Skin surface temperature measurements in horses
by electronic thermometry. The Veterinary Clinics of North America: Equine Practice, 19, 16–23.
Wagoner, D. (Ed.). (1999). Equine photos & drawings for conformation & anatomy. Tyler, TX: Equine
Research.
Wolfe, W. L., & Zissis, G. J. (Eds.). (1989). The infrared handbook. Ann Arbor: Environmental Research Institute of Michigan.