KUVASZ SOCCER

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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).

First, a diagram:

 Ta---------->|

        ^      |

  Ts    |    (a hair)

    |   L      |

    |   |      |

    v   v      |

-----------------------(skin)

Ta is the Temperature at the tip of the hair.



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.

 

 

Newtons's Formula:

         (Ta minus Ts)
C =  (F) x  -----------
 
L


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 conduct heat. 
L is the distance between the tip of the hair and the surface of the skin.

Dry oiless 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.

Okay, now 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.

Now, divide 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).

Now just play with numbers. Want to see what would happen if the dog's usual 6 inch coat was heavily matted? Just decrease L (Length).

What happens 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.

Pretty nifty, no?

With Newton's 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).

BTW: bird 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.

Jay Russell, Ph.D.
cotonnews@aol.com
http://members.aol.com/cotonnews/index.html


    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.

 
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