Thermoregulation

*This article was written back in April, but only getting around to posting it now! The cold snap may feel like a distant memory, but we all know the weather in this part of the world can be very changeable, so I haven’t counted on summer’s arrival yet!*

fia in the snowHere in Ireland, we’ve recently survived a cold-snap, where bread supplies were threatened, work places closed, and the country generally ground to a halt. Fia, my 8 year old greyhound, hadn’t seen a proper snow since she joined the family five years ago, so I was eager to see what she thought of it. Thankfully, it was a real hit! She loved tearing around in the snow, but despite her rather fetching jumper, she didn’t like staying out in the cold too long (unsurprising, for a greyhound!).

Anyway, it got me thinking that most of us don’t give that much thought to our dogs’ temperature, particularly in the winter time. Thermoregulation is most commonly discussed in the hot weather, but for many dogs, it should be a consideration in the colder weather too.

So today, I’m going to take a look at some of the science behind thermoregulation!

Temperature

Your dog’s temperature should be 38.3-39.2 celsius (it’s 37 for humans). Whilst most of us are happy to leave the task of taking a dog’s temperature rectally to the vet, in a recent blog post on pain in dogs I mentioned how good dogs are at hiding pain, so a thermometer can be a really useful tool for providing vital information about your dog’s health. If you suspect your dog isn’t feeling well, being able to take his temperature could help you decide whether or not he needs urgent input from the vet.

You can buy a pet thermometer from the likes of Amazon or viovet for about a tenner, and I think it’s a really good thing to have in your tool kit.

How dogs regulate their temperature

Maintaining an optimal temperature for the body to function is a feature of physiological homeostasis and is crucial to survival. Different species have various methods for regulating their temperature but animals can be largely categorised as either endotherms or ectotherms. Most mammals, humans and dogs included, are endotherms, which means they generate the heat they need to regulate their temperature internally (ectotherms, on the other hand, maintain their body temperature using external sources, for example, a lizard who lies on a hot rock to heat up).

Thermoregulatory strategies can be behavioural, physiological or anatomical. Behavioural strategies could include seeking shade in warm weather or getting close to another dog or human in cold weather, physiological strategies include shivering, panting or vasodilation (bringing blood from the core of the body to the skin where it can be cooled)/vasoconstriction (when blood vessels near the surface of the skin narrow to direct blood back to the core), whilst anatomical strategies include having fur or body fat.

Interesting Fact:

Countercurrant heat exchange occurs when heat from the hot blood in the arteries is transferred to the colder blood in the veins. Dogs have such a system in their paws, whereby the arteries and veins in the footpad are very close together, allowing warm blood in the artery to heat the blood in the veins which has been cooled by contact with the cold air or ground. This means that the blood is warmed up before returning to the body, allowing the body to be protected from any cooling effect and to keep the paws at a constant temperature.

This system can also be used for cooling. The brain is the organ most at risk from over-heating, so dogs have another counter currant heat exchanger between the carotid arteries and vessels to the brain, this time the heat from the arterial blood is cooled by the venous blood returning from the nose and mouth.

What affects thermoregulation in dogs

There are a number of factors that will affect how well your dog can regulate their temperature, including age, breed, size, weight, health, coat type, and even colour.

Age

Both puppies and older dogs are more susceptible to the effects of heat and cold, and less able to regulate their temperature, so extra care is required.

Breed

Certain breeds of dogs are better suited to hotter or colder climates. Huskies, with their thick double-layered coats for instance, will be much better at managing in colder weather than Staffordshire bull terriers, with their shorter coats. Greyhounds, who have both a thin, single coat, and a low percentage of body fat, will cope less well with extremes of temperature on either end of the spectrum.

Brachycephalic breeds (pugs, bulldogs, etc) tend to struggle in the heat as their inefficient panting effects their ability to cool down.

Size

Bergmann’s rule tells us that bigger body size allows for greater conservation of heat. Small dogs have a higher percentage of skin surface in relation to their overall mass, and so lose heat quicker.

Weight

Fat is an excellent insulator, so while dogs who have a high percentage of body fat are less likely to suffer from the effects of cold weather, they are more likely to suffer in hot weather.

Health

Dogs who are in less than optimal health will struggle to regulate their temperature.

Coat types

There are many different types of coat, each with different features. Some dogs are double coated- they have a shorter fluffy layer as an undercoat, and a hairier overcoat. These coats are very warm and insulating. On the other end of the spectrum you can find hairless dogs, such as the Chinese crested dog. In between, you’ll find curly poodle coats, corded Kommodor coats, single greyhound coats, all with varying abilities to insulate. As well as keeping dogs warm in cold weather, their coats can also function as a barrier to sun and heat, actually cooling them in the summer, so beware of having your dogs shaved for the summer months!

Colour

Dogs with dark coats will absorb heat from the sun, and suffer more from the effects of hot weather.

alfie cooling down

A cool, damp towel helps Alfie regulate his temperature in the hot weather.

 

Ensuring your dog is comfortable in the heat or the cold

Beds

Dogs spend a lot of time sleeping, so it’s really important that their sleeping area facilitates thermoregulation. Choice is paramount in this regard. Make sure that wherever your dog is sleeping, they have access to the floor in case they want to stretch out and cool down. Providing pillows and blankets can make their beds warm and cosy. Beds with comfortable high backs can help keep drafts off your dogs while they sleep and provide something to snuggle into. In particularly cold weather, offering a hot water bottle wrapped in towel may be welcome. If you’ve got a dog who feels the cold, think about how cold your house gets overnight. Pyjamas may be required, or you may wish to have the heat come on for a couple of hours at the time when the house would otherwise be at its coldest. You can also get beds which have a sleeping bag effect, so that the dog can burrow under the cover if they need shelter. When the weather is very hot, your dog may appreciate a damp towel on the ground that they can lie on if they get too hot.

If your dog is too cold or too warm they may have problems sleeping and move about, bark or ask to go out to the toilet overnight.

Walks

In extremes of temperature, you may wish to re-evaluate your dog’s exercise routine. In hot weather, the pavements can become burning hot, making any outdoor walking during the day very painful for your dog. Check the pavement by putting your hand on it for 5 seconds. Walking first thing in the morning or late at night can be better. During the day, you can do some nosework with your dog if they seem bored. Read more here!

alfie paddling

In the hot weather, a paddle in the sea will be a lot more pleasant than walking on hot concrete.

In cold weather, your dog may need a coat or jumper, depending on how cold it is, what age they are and what sort of natural coat they have. Avoid going out for long periods of time in the cold weather with your dog, and avoid putting them in situations where they have to stay still for too long. In the snow, be sure to pay extra attention to their paws- make sure that snow and ice don’t stick to the hair between their toes, and rinse their feet after walks if roads have been salted. You can also get special paw wax that can help protect their pads.

Clothes

Doggy clothes have never been more popular. However, many of the clothes produced are more for fashion than practicality. Clothes have the potential to make your dog uncomfortable and to hamper their movement, so it is important to choose wisely. I have found this to be particularly true with older dogs- my senior lad Alfie who was arthritic needed clothes that required no stepping into or wrestling legs in and out of.

My PDTE colleague Sonja has put together a great guide on coats for dogs, which you can read here.

I’ve mentioned pyjamas and for dogs who feel the cold, these can make a real difference.

alfie pjs

Fleece pyjamas kept Alfie warm in his old age.

The disadvantage of pyjamas is that the dog cannot remove them themselves, so I always feel these are best used under supervision so you can tell if your dog wants them taken off. Whilst indoors, I find the following useful indicators of my dog’s temperature:

  • Ears (cold ears alert me to a need for central heating or a layer of clothing/a blanket);
  • Curling up tight, or trying to get uncharacteristically close can be a sign of coldness;
  • Restlessness overnight- can occur when the dog is too hot or too cold;
  • Panting or lying stretched out in the coolest part of the room can indicate that your dog is too hot

In hot weather, cool coats which can reflect the light off dark coloured dogs can also be helpful whilst on walks. But again, try and get something that is going to be comfortable for your dog and not hamper their movement.

So, as we meander through the rather confused weather that spring can spring on us, it’s worth remembering these little things we can do to help our dogs feel more comfortable!

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