Forwarded by Lynn Swearingen:



Hot WEATHER RULES FOR RIDING

With the heat index increasing and the humidity as heavy as it is, be
sure to watch your horses.

If your total adds up to 180 or above don't ride, if it is 130-170 use
caution, 130 or below ride!

Determine: Temperature (F) + relative humidity (%) – wind speed
For example:
Temperature (F) 79
Relative Humidity (%) 58
Wind Speed 4.6 (MPH)
Answer = 132.4

Less than 130: All go—horses can function to cool themselves assuming
adequate hydration.
130 – 179: Caution—a horse's cooling mechanisms can only partially
function as intended. Some cooling management procedures will need to
be performed.
180 or above: Stop—a horse's cooling systems cannot and will not
function adequately. All cooling procedures will need to be utilized



SO IF THE TEMP IS 90 degrees or above and Humidity is 90 or above - DONT
GO!



This is a long article but well worth reading if you are riding in the
summer heat.
Chilling Out After Exercise
by: Ray Geor, BVSc, PhD, Dipl. ACVIM
The Horse, July 01 2001, Article # 897
http://www.thehorse.com/ViewArticle.aspx?ID=897
The mid-summer heat brings added challenges in managing the athletic
horse.
Regardless of whether your horse is competing in a show, trail ride, or
high-
level three-day event, hot weather places additional demands on his
body. You
need to be aware of these demands and take steps to ensure that he does
not
overheat. The focus of this article is prevention of overheating during
exercise in hot conditions. It will include recognizing the clinical
signs of
overheating, preparing the horse for exercise in the heat (improving
fitness
and acclimation to heat), and strategies for avoiding dehydration.

We will begin with a refresher on the effects of exercise and the
environment on the horse's body temperature.

Exercise in the Heat

The horse produces a tremendous amount of heat during exercise. Within
muscle,
the conversion of stored energy (for example, glycogen) into mechanical
work
(muscle contraction) is very inefficient, resulting in heat
accumulation. The
rate of heat production is related to the work effort--the faster the
horse
runs, the greater the rate of heat production. Similarly, steep terrain,
difficult footing, and weight carried (rider and tack)--all of which
increase
effort level--will increase the rate of heat production. At any given
work
level, the total amount of heat produced depends on the duration of the
exercise.

The horse, like all mammals, must operate within a fairly narrow range
of body
temperatures. At rest, rectal temperature is around 99-100ºF
(37.2-37.8ºC).
During exercise, the heat produced in contracting muscle spreads
throughout the
body, resulting in an overall increase in body temperature. A moderate
increase in body temperature (one to two degrees) is actually beneficial
to
body function during exercise (see "Warming Up to the Task", in the
April 2001
issue of The Horse). However, an excessive increase in temperature can
cause
tissue damage or death. The question is, how high is too high?

While there are no hard and fast rules, a rectal temperature above
106ºF (41ºC)
generally indicates the need for aggressive cooling procedures, while a
horse
with a rectal temperature of 108ºF (42ºC) or more can be at serious
risk for
heat stroke.

Under most circumstances, the horse is able to minimize the rise in body
temperature by dissipating heat from the body. The evaporation of sweat
from
the skin surface is the main means for heat dissipation. In fact,
evaporation
accounts for about 65-70% of the heat lost during and after exercise.
There
also is evaporative heat loss through the respiratory tract, and some
heat is
lost by radiation (emission in the forms of waves or particles) and
convection
(conduction) at the skin surface.

The horse also has a strategy for selectively cooling the brain
(maintaining
brain temperature lower than the rest of the body). This is important
because
the central nervous system is much more susceptible to the negative
effects of
high temperatures.

If you don't already have one, buy a good thermometer, and get in the
habit of
taking your horse's rectal temperature before and after exercise. These
measurements will allow you to develop an appreciation for the effects
of
exercise duration, effort, ambient temperature, and relative humidity on
body
temperature. In cool weather, there might be a two- to four-degree
increase in
temperature after a reasonably long ride. In hot weather there will be a
larger
increase in body temperature after the same amount of exercise.

Dispelling Excess Heat

The horse uses a couple of different strategies to deal with hotter
conditions.
First, sweating rates will be higher in an attempt to increase heat
loss over
the skin surface. Second, there will be an increase in breathing rate to
drive
evaporative heat loss through the respiratory tract and to keep the
brain cool.
Under dry heat conditions (hot, but with low relative humidity),
evaporative
cooling remains an effective means for heat loss. However, there is a
price to
pay--heavy losses of precious water and electrolytes can lead to
dehydration.
This can compound the effects of heat on body temperature because as the
horse
becomes dehydrated, there is a decrease in the efficiency of heat loss.

Heat and high relative humidity are not conducive to top-notch exercise
performance. Like humans, horses can struggle under these conditions
because
the rate of heat loss is greatly slowed. Efficient evaporation, both on
the
skin surface and through the lungs, occurs when the air is very dry and
therefore able to accept moisture as water vapor. As relative humidity
increases, there is less potential for evaporation because the air is
already
saturated with water, and sweating becomes a much less effective means
for heat loss.

The implications are twofold. First, during exercise in hot and humid
conditions, body temperature will increase at a much faster rate--up to
twice
as fast. Therefore, that critical upper limit in body temperatur
e will be
reached much quicker than would be the case in cool conditions. Second,
unless
we make attempts to actively cool the horse, recovery following exercise
will be delayed.

How well an individual horse copes with hot, humid weather depends on
several
factors. Body type is important--a big, heavy horse will overheat faster
than a
smaller, leaner individual. The amount of heat produced and the rate of
heat
loss depend partly on muscle mass and the ratio of body mass to skin
surface
area. Heavily muscled horses have a larger body mass to surface area
ratio than
leaner animals, which favors heat retention. This helps explain why
lighter
breeds (Arabs, Thoroughbreds, and crosses) are better suited for
endurance events.

The length of the hair coat is also important. A long winter coat will
trap
heat in the body. Horses in heavy training programs might need to be
clipped in
early spring to minimize this insulation effect and to minimize heat
stress as
the conditioning program is stepped up during the spring.

Physical conditioning and heat acclimatization also influence tolerance
to work
in the heat. A poorly conditioned, overweight horse can be at high risk
for
overheating if worked too hard in hot conditions. For one, body fat acts
as an
insulator, impeding heat loss. Second, physical conditioning results in
a
number of adaptations that improve temperature regulation during
exercise. With
training, muscles work more efficiently and produce slightly less heat.
The
cardiovascular system is also better able to move heat from the site of
production (muscle) to the skin. Training also increases the efficiency
of
sweating. Therefore, it is imperative that your horse undergo a training
program that is appropriate for the work he will be doing.

Studies conducted in advance of the 1996 Summer Olympic Games in Atlanta
showed
that training in the heat results in further adaptations that aid
temperature
regulation during exercise. To some extent, training during the
transition from
the cool weather of winter and early spring to the warmer temperatures
of
summer will acclimatize the horse to the hotter conditions. However,
when a
horse is shipped from the cold North to the warm, humid southern states,
some
lead time is required to ensure adequate acclimatization. You should
plan on a
minimum of two to three weeks to account for the time needed to recover
from
transport and to allow for a period of conditioning in the hot climate.

As mentioned, hydration status also influences the efficiency of heat
loss.
With dehydration, the cardiovascular system is less able to move heat to
the
skin surface, and less fluid is available for sweating. This means that
a
dehydrated horse will overheat faster than a well-hydrated horse.

Dehydration can, in particular, be a problem for endurance horses or
horses
engaged in other long work sessions. In hot conditions, horses can lose
2.6-3.9
gallons (10-15 liters) of sweat fluid per hour of exercise, so during
long
rides you should let your horse drink as often as possible. For
endurance
rides, some electrolytes should also be given during the ride (see
"Fluids and
Electrolytes" in the April 2000 issue of The Horse, online at
http://www.thehorse.com/ViewArticle.aspx?ID=214).

By and large, the risk of overheating and developing heat stroke is
greatest
during the summer months. However, heat stroke can occur at other times.
For
example, very warm, even hot days can occur in spring. So, it is
possible that
an unacclimatized horse in the early phase of its conditioning program
will be
asked to exercise in fairly hot conditions. Under those circumstances,
one
should reduce the time and/or intensity of the exercise bout to avoid
heat
stress.

Recognizing Overheating

Close monitoring of your horse's vital signs is very important when
training
and competing in warm conditions. Rectal temperature, pulse rate, and
respiration rate should be recorded before and after the ride. For long
exercise sessions, these measurements also should be taken at regular
intervals
during the ride. The facial artery, located below the cheekbone at the
halter
check-piece, is perhaps the easiest place to check pulse rate.
Monitoring pulse
rate will take some mastering, but will become second nature with
practice.

The pulse rate will be high immediately after exercise (80 to 100 beats
per
minute), but in fit horses will decline quickly during recovery time.
With 15
minutes of recovery, the pulse rate is often 40-50 beats per minute or
even
near resting values (35-45 beats per minute). The post-exercise decrease
in
pulse rate is somewhat slower in hot, dehydrated horses. However,
respiration
rate and rectal temperature will give you the best indications of heat
stress.

The normal resting respiratory rate is 10-20 breaths per minute. Even in
cool
conditions, the respiration rate will be elevated for 30 minutes to an
hour
after hard exercise. It might remain at 60-80 breaths per minute for the
first
10 minutes of recovery.


Hot horses will have much higher breathing rates, as high as 120-140
breaths or
more per minute. This makes sense because the horse is using the
respiratory
system to lose heat. However, you should be concerned when the
respiratory rate
remains this high after five to 10 minutes of rest. This indicates that
the
horse is overheated and in need of active cooling.

During recovery, monitor the horse's rectal temperature at regular
intervals.
In overheated horses, rectal temperature might decline very little or
even
increase slightly during the initial 10-20 minutes of recovery. This is
evidence that aggressive cooling is necessary. As mentioned, you should
be
concerned when rectal temperature is over 105-106ºF (40.5-
41ºC).

You might notice other signs of heat stress, such as lethargy or lacking
his
normal "zip." Do not ignore these signs; stop exercise right away, move
the
horse into the shade, and cool him out. There is a fine line between
heat
stress and full-blown heat stroke, so it is absolutely essential to
remain on
the side of caution.

Aggressive Cooling

Traditionally, tossing cold water on hot horses has been regarded as a
"no-no"
because of the misbelief that this practice would result in muscle
damage and
tying-up. Field and laboratory research over the past decade has largely
dispelled this myth. Rather, it is probably the very high muscle
temperatures
(110ºF or 43.3ºC or more) that cause muscle damage. The bottom line is
that
applying cold water is the most practical and effective means to assist
cooling-
-and it is safe.

You need a plentiful source of cold water (35-40ºF or 1.6-4.4ºC), a
means for
applying the water (e.g., plastic buckets), and a scraper to remove
excess
water. You can use sponges dipped in cold water, but this is a much less
efficient method compared to hosing or pouring water on the horse. Water
applied in this fashion will warm up almost immediately, so the water
should be
scraped off quickly and fresh, cool water re-applied to cool the horse
down.

This explains why it is not a good idea to drape wet towels over the
horse.
Although there will be a brief cooling effect from the towel, unless you
keep
pouring water on the towel, it will warm up and impede heat loss by
insulating
the horse.

This dousing process should be continued until the horse's rectal
temperature
is below 101ºF (38ºC). Importantly, if your horse does not cool out
within 40-
60 minutes, you should call a veterinarian.

It is also preferable to put the horse in the shade while cooling him.
Try not
to shelter him from any breeze, as the wind will help with convective
cooling.
Electric fans can also be placed in front of the horse. It is fine to
keep the
horse moving during this cooling off process (e.g., walking in a
smallish
circle). However, it is not necessary for the cool-down to be any more
active.
More exercise will simply further delay the decrease in body
temperature.

Hi Guys,
I thought this was worth passing on. One of the best articles I have
seen on hot weather riding.
It was in The SFTR newsletter.
Let the Horse Drink

Another important part of the cooling process is drinking.
Traditionally,
horsemen have not allowed "hot" horses to drink because of a perceived
risk of
colic and cold-water founder (laminitis). However, with the possible
exception
of very hard galloping exercise (e.g., Thoroughbred racing), it is safe
for
horses to drink right after exercise. In fact, the thirst drive
decreases with
time after exercise, so offer water as soon as is practical. Let the
horse
drink up to one to two gallons during the first 15 minutes of recovery.

Remember that you are the best advocate for your horse. Ensure that he
is thoroughly conditioned,
acclimatized, closely monitored during exercise, and
actively cooled after the ride or event to keep him from getting heat
stress and heat stroke.


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