Clipping Double Coated Breeds

[Willem]

[Dogs coats are NOT transparent, so the car example is irrelevant.

that's the point, take away the coat and the skin respectively the blood will absorb the sun radiation heating up the whole body (pretty the same like a reverse AC heating up a room in winter (with the cooling agent = blood) - unfortunately, for the dog in this case the heat transfer happens in summer. Problem for the dog's skin is that it can't dispatch the surplus heat via radiation (as you pointed out), nor via evaporation (like humans), so the only way is panting (via mouth) and a little bit via convection over the skin which is minimal due to the still very low temperature difference and the low heat coefficient of air as the major drivers for convection.

Edited October 24, 2015 by Willem

[Willem]

and yes, for medical and hygienic reasons (no one wants to breed maggots in a dog's fur) it maybe recommended to clip a dog's coat from time to time despite the physics (which - the physics - might also be negligible for some breeds where the fur follows more fashion than function...)

[sandgrubber]

[Dogs coats are NOT transparent, so the car example is irrelevant.

that's the point, take away the coat and the skin respectively the blood will absorb the sun radiation heating up the whole body (pretty the same like a reverse AC heating up a room in winter (with the cooling agent = blood) - unfortunately, for the dog in this case the heat transfer happens in summer. Problem for the dog's skin is that it can't dispatch the surplus heat via radiation (as you pointed out), nor via evaporation (like humans), so the only way is panting (via mouth) and a little bit via convection over the skin which is minimal due to the still very low temperature difference and the low heat coefficient of air as the major drivers for convection.

We all deal with thermodynamics on a daily basis though few people understand it.

Cooling via panting is actually pretty effective, at least if it isn't humid (evaporative coolers don't work well when it's muggy). The dog's nose contains some nice equipment for evaporative cooling . . . these are good at bringing down the core temperature. Lots of blood transport involved. The brachy breeds are handicapped in this and handle heat very badly, hence they tend to overheat, and airlines tend to ban them.

I still don't get your model. Are you saying that heat gain from solar radiation is higher than heat gain through metabolism?. In most cases this isn't true, and hot dogs can and do seek shade to avoid radiative warming from direct sunlight. They're not dumb! The full model must recognize that warm blood metabolism generates a fair amount of heat, and requires a relatively constant core temperature to stay alive. Dogs that evolved in cold climates have wonderful insulation. Unfortunately, this backfires when they are put into hot, especially hot-humid (so the evaporative cooling system gets crippled) environments.

Usually Temp(dog) is higher than Temp(air) and the dog has no trouble shedding body energy. When Temp(air) gets higher, it gets harder to keep energy in balance. Having a thick coat makes it harder to keep balance.

Blood is a cooling agent when it moves from the dog's nose--cooled by evaporative cooling--to the core, brain, etc.. Elsewhere, muscles etc. generate heat from metabolism, and the circulatory system evens out temperature between parts of the body. There's also some amazing blood warming stuff that goes on in the feet and allows dogs to walk on frozen ground for hour after hour.

Try playing around with your mobile phone or a lightbulb -- both of which are warmed by internal energetics (electricity not metabolic, but heat is heat. . . it behaves the same regardless of how it was generated). Not a bad analog for a dog that is heated by metabolic processes. Experiment with putting fabric over the body . . . stick a thermometer in. You will see that they tend to heat up when given an insulating layer: in the case of the phone, by a few degrees; a lot more in the case of the light bulb.

[Willem]

... Are you saying that heat gain from solar radiation is higher than heat gain through metabolism?. In most cases this isn't true, and hot dogs can and do seek shade to avoid radiative warming from direct sunlight.

let's crunch some numbers:

... one of my food packages for the dog states: 350 kcal/100 g metabolizable energy; feeding my dog (17 kg) 250 gr equals approx. 900 kcal (it's actually 875 kcal, but let's keep it easy) or 3.7 MJ - only a part of this energy is transferred into heat as the dog runs respectively does physical work over the day.

Now let's assume I roll out my entire garden hose in the garden and we have a sunny day with 25 deg C air temperature (yes, there will be temp variation - let's keep it simple) - the garden hose holds 17 kg water (to allow comparison with my dog's weight - it would need to be a pretty long garden hose so...however, dogs body - like humans - are mostly made out of water so it will allow for some comparison). After 2-3 hours laying in the sun the water in the garden hose gets pretty hot and hit peak temperature of approx. 50 deg C where it stays for a while till the sun goes down. At this peak point where it reaches 50 deg C the energy intake into the hose via radiation equals the energy outtake via conduction (laying on the grass) and convection (via the air). Now, just to get the hose to the 50 deg C (we know this is easily possible) it needs at least the following heat energy: delta temp. x mass x heat capacity of water...if I got the math right that equals approx. 2.5 MJ (assuming a tap water temp = 15 deg C, heat capacity of water = 4.18 kJ/kgK)...in approx. 2-3 hours. The real heat intake via radiation will be even higher as I neglected the losses via conduction to the ground / grass and convection to the air (and the amount the hose radiates back - but that is really negligible).

Now we have 2.5 MJ in 2-3 hours (0.8 MJ per hour) vs 3.7 MJ metabolizable energy (where only a part is transferred in heat energy) in 24 hours (0.15 MJ per hour)...pretty impressive figures indicating the heat intake via radiation can be indeed significant higher than the metabolizing energy.

Of course the dog would try to find some shade (if they allowed to do so), but also here the indirect radiation will allow for some substantial additional heat intake every creature has to cope with.

You could argue now that the looooong garden hose will provide much more surface compared to the compact body of a dog thus the radiation into the dog's body is significant less...well, then look at the old water solar heater drums on the roofs, the radiation does the job here too.

Here is a question for you: lets assume we could breed a dog with a coat that provides a 'perfect' insulation and with 'perfect' I mean an insulation where heat transfer in both direction is close to zero. Equipped with such a coat the dogs natural temperature regulating system (panting = evaporation cooling through the mouth / nose) just has to cope with the metabolizing energy depending on the activity level - it wouldn't matter whether it is too hot or too cold outside because there is no heat transfer through the 'perfect' coat at all....so why would you take this coat off for summer?

[juice]

Can anyone recommend a good tool for removing undercoat from a double coated dog who is terrified of the groomers? I brush him daily, but it just keeps coming out ,and his undercoat is really thick.

[Lhok]

To be honest while the conversation is very interesting regarding the science, I do have to wonder about double coated breeds that were bred for the desert/hot climates. Canaan dogs,Cattle dogs and Anatolians hell even the desert dingoes of Aus have double coats so it isn't always for the colder climates.

I also have to wonder if humidity is the reason why most dogs when clipped down feel better or act like they are happier. Even humans struggle in very humid climates so I would imagine that a dog with a coat who only really has to rely on panting/pads and digging a hole to lay down in they would have a really awful time. Actually thinking about this and thinking of the dingoes only the northern ones lack the double coat so I am now really wondering if humidity is the key here rather then hot vs cold.

--Lhok

[Pjrt]

A short double coat or a long double coat? Breed?

Personally i am not a fan of undercaot rakes, but the longer the coat, the longer the tynes need to be to be effective. A horse curry or rake is fine for a short coat, a dog undercoat rake with longer teeth for a fuller longer coat.

Personally I dont think anything beats a slicker brush and a steel comb and a thorough going over once or more a week. Push the hair up and back and work through it methodically, called line grooming. Enhance results by very lightly misting the the sections with a spray bottle of water with a drop of conditioner mixed in.

Raking goes through and over the coat and will never work as well as line grooming, but line grooming requires a little more patience and effort.

The very best way to do a thorough undercoat cleanout is to bath the dog and dry it with a forced air dryer. followed by a good brush and comb.

If the dog is petrified of dryers, bath, towel off vigorously, keep the dog confined to a clean area and let it air dry about 75%, or take it for a walk in the sun on a clean surface, then when it is almost dry, brush and comb until it is dry. This method works really well for scared dogs. Not as completely effective as force drying, but better than dry grooming.

[*kirty*]

Can I just mention something regarding the dog/car issue - you are talking about a car parked in the sun. Most dogs are not sitting in the full sun all day. They are lying in the shade or in the house etc so insulation from direct sun is irrelevant.

[Willem]

To be honest while the conversation is very interesting regarding the science, I do have to wonder about double coated breeds that were bred for the desert/hot climates. Canaan dogs,Cattle dogs and Anatolians hell even the desert dingoes of Aus have double coats so it isn't always for the colder climates.

I also have to wonder if humidity is the reason why most dogs when clipped down feel better or act like they are happier. Even humans struggle in very humid climates so I would imagine that a dog with a coat who only really has to rely on panting/pads and digging a hole to lay down in they would have a really awful time. Actually thinking about this and thinking of the dingoes only the northern ones lack the double coat so I am now really wondering if humidity is the key here rather then hot vs cold.

--Lhok

good point - obviously evaporation cooling doesn't work very well if humidity is already up, however the increased water conc. in the air would increase the heat capacity of the wet air thus improving the convection cooling....I didn't know that about the dingoes that the northern ones lack the double coat....interesting, ingenuity of evolution?

Edited October 25, 2015 by Willem

[RuralPug]

Am totally loving this conversation. It is great to learn more about the science, and quite a lot of interesting points. I maybe now will be happier to clip a mostly indoor dog on request and will continue to try to convince owners with outdoor dogs to let me thin out the undercoat without touching the topcoat.

Lhok, that was a great point about the dingo, I had known that Alpine and Desert dingoes are double coated and that Tropical dingoes are single coated but I had never before thought to see the relevance to the clip vs thin argument. That is the clincher for me, natural selection over 30,000 years is most likely to get it right.

[JulesP]

Can anyone recommend a good tool for removing undercoat from a double coated dog who is terrified of the groomers? I brush him daily, but it just keeps coming out ,and his undercoat is really thick.

My fav is the Les Pooches slicker brush. Expensive but great for dogs that aren't fans of being brushed.

[Pjrt]

Can anyone recommend a good tool for removing undercoat from a double coated dog who is terrified of the groomers? I brush him daily, but it just keeps coming out ,and his undercoat is really thick.

My fav is the Les Pooches slicker brush. Expensive but great for dogs that aren't fans of being brushed.

Im a LesPooch junkie. I have about 10 of them!

[juice]

Thankyou, i'm not sure wether he is classed as long or short, so have attached a pic, its like BC but thick.

I did bath him and brush and comb it out when it was almost dry last week ( was scared of the dryer), but he is getting on and has arthritis in his rear end, which is where most of the coat seems to be, around his tail and he has a skirt, and he gets uncomfortable if i brush there for long.

[Pjrt]

Thankyou, i'm not sure wether he is classed as long or short, so have attached a pic, its like BC but thick.

I did bath him and brush and comb it out when it was almost dry last week ( was scared of the dryer), but he is getting on and has arthritis in his rear end, which is where most of the coat seems to be, around his tail and he has a skirt, and he gets uncomfortable if i brush there for long.

Probably short thick , or medium double coat.

If he is getting on best to just do what he can cope with. Sounds like you're doing fine. Anything is better than nothing. For reducing heat stress it's mostly the body, neck, chest area to concentrate on removing as much dead coat as possible. It won't make a whole lot of difference for heat stress if his pants are a bit thick. Age can bring conditions that will thicken coat and over produce coat, such as cushings. If you think his coat is really over doing it, it may be worth watching and checking for other health issues.

[juice]

Ok, thanks, they are inside if it gets too warm in the aircon, and have plenty of undercover shade outside too.

[Mim]

To be honest while the conversation is very interesting regarding the science, I do have to wonder about double coated breeds that were bred for the desert/hot climates. Canaan dogs,Cattle dogs and Anatolians hell even the desert dingoes of Aus have double coats so it isn't always for the colder climates.

I also have to wonder if humidity is the reason why most dogs when clipped down feel better or act like they are happier. Even humans struggle in very humid climates so I would imagine that a dog with a coat who only really has to rely on panting/pads and digging a hole to lay down in they would have a really awful time. Actually thinking about this and thinking of the dingoes only the northern ones lack the double coat so I am now really wondering if humidity is the key here rather then hot vs cold.

--Lhok

I was reading about this just recently for a uni assignment. I was reading specifically about the thick coats of camels but it can be applied to other animals, like dogs, who have thick coats in very hot environments. Basically, thick coats actually reflect heat energy from the sun, rather than absorb it, so it's like having a special coat on that bounces heat away from you and keeps you cool underneath. This links to your humidity theory well because these desert animals with thick coats don't have to deal with humidity. So I would agree with you that it seems that thick coats struggle with the Australian humidity, rather than the heat.

Edited October 25, 2015 by Mim

[sandgrubber]

To be honest while the conversation is very interesting regarding the science, I do have to wonder about double coated breeds that were bred for the desert/hot climates. Canaan dogs,Cattle dogs and Anatolians hell even the desert dingoes of Aus have double coats so it isn't always for the colder climates.

I also have to wonder if humidity is the reason why most dogs when clipped down feel better or act like they are happier. Even humans struggle in very humid climates so I would imagine that a dog with a coat who only really has to rely on panting/pads and digging a hole to lay down in they would have a really awful time. Actually thinking about this and thinking of the dingoes only the northern ones lack the double coat so I am now really wondering if humidity is the key here rather then hot vs cold.

--Lhok

I was reading about this just recently for a uni assignment. I was reading specifically about the thick coats of camels but it can be applied to other animals, like dogs, who have thick coats in very hot environments. Basically, thick coats actually reflect heat energy from the sun, rather than absorb it, so it's like having a special coat on that bounces heat away from you and keeps you cool underneath. This links to your humidity theory well because these desert animals with thick coats don't have to deal with humidity. So I would agree with you that it seems that thick coats struggle with the Australian humidity, rather than the heat.

Please give references. The fraction of incoming solar radiation that is reflected is called "albedo" in physics. It aligns pretty closely, but not exactly, with color. I have never seen comparison of sun effects on a white vs. a black dog . . . would be helpful to know.

Also recognize that there are other reasons for a thick coat. In the case of camels, abrasion by wind blown sand could be pretty nasty.

Another set of question marks is raised by the definition of "double coat". Thin overcoat over thin undercoat is quite different from thick undercoat with water-shedding overcoat. The physics of boundary layers . . . and insulation generally . . . can be complicated as they get into turbulent flux, an area that drives even rocket scientists crazy. It's quite possible that evolution has come up with some coat patterns that are superbly suited to desert conditions . . . but may not look like it.

[sandgrubber]

... Are you saying that heat gain from solar radiation is higher than heat gain through metabolism?. In most cases this isn't true, and hot dogs can and do seek shade to avoid radiative warming from direct sunlight.

let's crunch some numbers:

... one of my food packages for the dog states: 350 kcal/100 g metabolizable energy; feeding my dog (17 kg) 250 gr equals approx. 900 kcal (it's actually 875 kcal, but let's keep it easy) or 3.7 MJ - only a part of this energy is transferred into heat as the dog runs respectively does physical work over the day.

Now let's assume I roll out my entire garden hose in the garden and we have a sunny day with 25 deg C air temperature (yes, there will be temp variation - let's keep it simple) - the garden hose holds 17 kg water (to allow comparison with my dog's weight - it would need to be a pretty long garden hose so...however, dogs body - like humans - are mostly made out of water so it will allow for some comparison). After 2-3 hours laying in the sun the water in the garden hose gets pretty hot and hit peak temperature of approx. 50 deg C where it stays for a while till the sun goes down. At this peak point where it reaches 50 deg C the energy intake into the hose via radiation equals the energy outtake via conduction (laying on the grass) and convection (via the air). Now, just to get the hose to the 50 deg C (we know this is easily possible) it needs at least the following heat energy: delta temp. x mass x heat capacity of water...if I got the math right that equals approx. 2.5 MJ (assuming a tap water temp = 15 deg C, heat capacity of water = 4.18 kJ/kgK)...in approx. 2-3 hours. The real heat intake via radiation will be even higher as I neglected the losses via conduction to the ground / grass and convection to the air (and the amount the hose radiates back - but that is really negligible).

Now we have 2.5 MJ in 2-3 hours (0.8 MJ per hour) vs 3.7 MJ metabolizable energy (where only a part is transferred in heat energy) in 24 hours (0.15 MJ per hour)...pretty impressive figures indicating the heat intake via radiation can be indeed significant higher than the metabolizing energy.

Of course the dog would try to find some shade (if they allowed to do so), but also here the indirect radiation will allow for some substantial additional heat intake every creature has to cope with.

You could argue now that the looooong garden hose will provide much more surface compared to the compact body of a dog thus the radiation into the dog's body is significant less...well, then look at the old water solar heater drums on the roofs, the radiation does the job here too.

Here is a question for you: lets assume we could breed a dog with a coat that provides a 'perfect' insulation and with 'perfect' I mean an insulation where heat transfer in both direction is close to zero. Equipped with such a coat the dogs natural temperature regulating system (panting = evaporation cooling through the mouth / nose) just has to cope with the metabolizing energy depending on the activity level - it wouldn't matter whether it is too hot or too cold outside because there is no heat transfer through the 'perfect' coat at all....so why would you take this coat off for summer?

There's a MAJOR difference in geometry between a dog and a garden hose. Compare surface to volume ratios... simplify by assuming both are cylindrical. The dog has a radius of what, say 100 mm. The hose more like 20 mm. If you follow through the geometry, the hose would absorb 5x as much energy per unit length as the dog. If the dog is 1 m long and the hose is 10 meters, there's a fiftyfold difference in surface/volume.

a major factor in absorbtion of radiation/kg mass. Also note that the hose cannot cool itself using evaporative cooling. Moreover, anyone who leaves a dog in direct sun on a hot day is guilty of animal cruelty.

"Perfect insulation" is about as realistic as perpetual motion. If we could create perfect insulation in smallish objects, we could have freezers that required almost no energy, and the cost of approaching absolute zero would be vastly smaller. To obtain even a freezer that doesn't cost the earth to cool requires 50+ mm of rigid, closed cell foam like substance . . . probably much more effective insulation than the thickest of dog coats. (Has anyone seen anything written on the R value of dogs' coats? Would be interesting to have this information to model this question).

A perfectly insulated dog would cook; more rapidly if it was active and ate a lot. Dogs evolved to thermoregulate in environments that are, on average, at least 10 degrees below the dog's core temperature (Average global temperature is around 14 C . . . warmer in say, savannah regions where many dogs seem to originate . . . but still nowhere near a daily average of 39C. I don't think anyplace on earth even has an average daily maximum temperature above 35 C. Remember, Iditerod dogs begin to suffer overheating when temperatures go above freezing.

here's a relevant link . . . looks like daily averages above 30 C are few and far between. http://www.wunderground.com/blog/weatherhistorian/warmest-places-on-earth-average-annual-temperature

If you have 3.7 MJ a day (btw. work energy degrades to heat . . . remember entropy) energy input and zero energy output you're going to end up pretty damn hot.

p.s. the study of mammology regards panting as more effective than sweating in two dimensions. First, panting is easier to regulate. Second, it doesn't cause loss of electrolytes (salt in sweat). On the negative side, panting requires energy and generates heat. As usual, biology is complicated ;) . See, eg., https://books.google.com/books?id=Ugq5BgAAQBAJ&pg=PA201&lpg=PA201&dq=evaporative+cooling+mammals&source=bl&ots=waPfv9hE_B&sig=ichtssKbQKKqcclmz1ZC2fCic6E&hl=en&sa=X&ved=0CEoQ6AEwCGoVChMIv9mhlerdyAIVRuUmCh1OaQAd#v=onepage&q=evaporative%20cooling%20mammals&f=false

Edited October 25, 2015 by sandgrubber

[RiverStar-Aura]

Juice, you could try a Zoom Groom on him.

[Willem]

There's a MAJOR difference in geometry between a dog and a garden hose.

Are you absolutely sure?..... :D

...it seems that the few things we have in common are loving dogs and not liking FB (and other anti social media), but it seems we can't agree on the physics for this entertaining debate. Now that (the disagreement about the physics) is not really a problem and all the comments given might help other dog owners making the right decision whether they want to clip or not to clip and how short etc...so I will leave it at that admitting that obviously I can't find a suitable analogy for you that would proof my points :) .