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There are frequent debates among Kuvasz owners about the value or harm in
shaving dogs during the summer months, and often new owners don't know what
to believe. In fact, strangers often approach me when the weather is hot and
tell me I should shave my dogs. At that point I always invite them to feel
how cool the fur is close to the skin. However I didn't know the technical
formula or biophysics of the fur cooling process, until Dr. Jay Russell sent
the following note to a dog email list.
Now you too can have the facts at your disposal while you are waiting for
the movie to download.
HAIR LENGTH and TEMPERATURE TOLERANCE
by Jay Russell Ph.D.
If your LGD
is dark-coated, then it will absorb heat from solar radiation quickly; if
your LGD is light-coated, it will absorb heat from solar radiation slowly.
Eventually, all things will attain an equilibrium, but it is the speed at
which that equilibrium state occurs that usually chills us mammals to the
bone or fries us like bacon. Color aside, your LGD's hair length and coat
condition are crucial factors determining its ability to tolerate the daytime
heat load. It is actually all biophysics (mostly Newton's Law of Cooling) and
it is not difficult to get a grasp of the concepts involved (trust me on this).
| (a hair)
| | |
v v |
is the Temperature at the tip of the
Ts is the Temperature at the surface of the skin.
L is the distance between the tip of the hair and the
surface of the skin.
(Ta minus Ts)
C = (F) x -----------
C is conductance, the speed at which the Temperature at the tip of the hair
(Ta), will be equal
to the Temperature at the skin's surface (Ts).
F is a number,
determined through experiment, which estimates the ability of a hair to
L is the distance
between the tip of the hair and the surface of the skin.
hair (like that of a Coton de Tulear) has a very small number, while silky,
oily hair has a very big number. The bigger the number F, then the faster the dog will
gain or lose heat at the surface of the skin. I'll ignore it here. NB: to
my knowledge, this number has never been determined for any dog.
a few facts. Most mammals attempt to keep their skin temperature at about
85 degrees F (29 deg C). The sun can heat the tip of a hair to more than
150 degrees F (66 deg C). Plug in those temps to the formula and you get
(Ta - Ts) is (150 - 85) which is 65, a big number.
that number by the length of the hair (for metric-philes, just use cms).
If the hair is 6 inches long, then the number C shrinks to 10.8. The dog's skin will stay
cool longer. If the dog has been clipped to 1
inch, then conductance, C, will remain at 65 and the dog's skin will heat quickly. And, if you surgically
clip Fido to say 1/8th of an inch, then you'd divide 65 by 0.125 and get a conductance value C of 520. The dog's skin temperature would equal the hair tip's temperature in a twinkling of an eye (i.e.,
divide 520 by 65 and you see that heat will transfer eight times
faster than it would
if you had left the hair at 1 inch long).
play with numbers. Want to see what would happen if the dog's usual 6 inch
coat was heavily matted? Just decrease L (Length).
if it is night time and the ambient temperature drops to 40 degrees? Just
substitute 40 for
Ta (hair tip temp) C will be a negative number,
indicating that your pooch is loosing skin heat towards the tip of its hair
and the environment beyond).
If a dog
exercises, then its Ts (temp of skin) will increase
as its body attempts to dump the heat load to the outside. A dog will pant
when its Ts is
high and the Ta is high and/or when itsTs is high andF is low. If a dog is really suffering, soaking it with water
quickly makes F (number, determined through
experiment, which estimates the ability of a hair to conduct heat) a big number (water is much more conductive than cotton or air
or normal hair, for example) and simultaneously flattens the coat making L
a small number. A matted coat impedes the dogs own ability to vary L (which it normally does by
erecting or flattening its topcoat hairs using the follicle's tiny erector
muscles) and mats also alter the F value, probably making F a smaller number. Matted dogs cannot dump heat from their
skin surface to the outside air, a potentially dangerous situation.
formula, you can get a glimpse of what your dog might be feeling (no small
accomplishment for us thin-haired, sweaty-skinned primates who are obsessed
with adulterating hair, changing its reflectivity, varying its length, and
otherwise messing with Mom Nature).
fanciers can play with this formula and gain insight into why a bird fluffs
up its feathers or flattens them. Bird feathers are known to have a really
small value for F showing that feathers (modified
reptilian scales) are waaaaay better than typical mammalian hair at slowing
down thermal conduction. That's why you might have a down jacket rather than one
stuffed with Anatolian clippings. There's no substitute for a big L and a little Fwhen it comes to outerwear.
Oh yes, one
last point. For those of you with a hairless breed, the formula doesn't work
because there is no L to consider. A Xolo or Chinese Crested is at the whim
of the sun and the air. A naked LGD would be a pretty unhappy dude.
Kuvasz are generally smart enough to find a shady area on a hot sunny day.
Moreover their white coats don't readily attract the sun's rays, and the
melanocyte cells in their darkly pigmented skin help protect against solar
damage. However, while they may not be as susceptible as some breeds like
Dalmations or white Bull Terriers, if they are sunburned repeatedly because
their fur is closely cropped, or sun damaged on the face where the fur is
very short, they can develop a condition called actinic keratosis. This in
turn can become a malignant form of cancer called squamous cell carcinoma.
Enough said on the topics of heat, sun, and shaving.
Kuvasz playing soccer? Yes in a 1.67MB Quicktime movie!