All posts by HotDogsCanineHeatstroke

We are a team of researchers investigating heatstroke in dogs.

Dogs in hot cars: is the risk just a summer one?

Over 75% of dog owners use their car to transport or house their dog, but cars get hot. The ‘Dogs in Hot Cars’ campaign sends out a clear message every year that leaving a dog in a hot car is dangerous and potentially fatal for a dog. Despite this, over 8000 calls were made to the RSPCA in 2018 over concerns for dogs left in hot cars. The risk period tends to be associated with summer, and the campaign normally starts around May time. With an increasingly unpredictable climate and increase in intensity and frequency of heatwaves, the year round risk of car temperatures needs further investigation.

Our latest study looked at temperatures falling outside the range of 8-25°C . Broadly speaking, 25°C is the upper comfortable threshold for dogs to control their body temperature, slightly above the upper limit for some brachycephalic dogs to cool themselves unaided. This range is also the temperature threshold for the storage of many veterinary and human drugs, outside of which they can lose their efficacy with potentially dangerous consequences. An additional threshold over 35°C was included, at which point all dogs struggle to thermoregulate, particularly when enclosed in a car with no air movement.

The internal temperatures of four cars were monitored over a two-year period. This allowed us to monitor the temperatures 24 hours a day (no dogs were kept in the cars for the purposes of the study!). By the end of the study period, we had between 7300 and 17800 individual temperature readings for each month of the year. This allowed us to look at the impact of time of day and seasonality on internal car temperature.

UK car temperatures

Internal car temperature ranged from -7.4°C to 54.5°C with temperatures dropping below 8°C in every month except June and July. Temperatures exceeded 25°C in every month of the year and above 35°C from April to September. And whilst early mornings were generally cooler, temperatures over 35°C were recorded between 8am and 9pm.

The highest temperature recorded was 54.5°C

It is also worth bearing in mind that the risk may extend beyond stationary vehicles. Sitting in traffic on a hot day, or an air conditioning system failure could also be lethal for dogs trapped in the car.

This study highlights the year round risk to dogs in cars and the need for constant vigilance. This is particularly the case for those breeds and types of dogs considered more at risk of heatstroke, such as brachycephalic, overweight and older dogs.

The study highlights that the risk to dogs in cars is year round, not just restricted to the traditionally warmer summer months. Heat-related illness can be fatal so whenever dogs are in cars, owners should be cautious. Whilst traditionally the advice is to avoid exercise during the midday heat, peak car temperatures occurred between 14:00 and 17:00 hours from March to October. So late afternoon, from spring to autumn is the most at dangerous time for dogs in cars.

To read the full article click here.

Hot dogs – the UK dogs most likely to experience heat-related illness

After what feels like an eternity (and is in fact just under 2 years!) we can FINALLY share the first set of results from our Hot Dogs VetCompass project – exploring the risk factors, incidence and fatality of heat-related illness in UK dogs.

The paper is fully open access, so you can either view it on-line here:

https://www.nature.com/articles/s41598-020-66015-8

Or download the PDF here:

We have a conversation article that summarises the key findings available here: https://theconversation.com/nine-dog-breeds-at-higher-risk-of-heatstroke-and-what-you-can-do-to-prevent-it-139501

Or, for the super short version, check out our infographic, designed by Becky – www.PawPrintsPosters.com

Hot Dogs research presented at BSAVA Congress 2020 .

You may have been wondering where we’ve been and what we’ve been up to, as it seems an age since we last shared any updates on our canine heatstroke research project…

Well, we finally have some exciting news!

Hot Dogs at BSAVA Congress 2020

Last month Emily presented two abstracts (preliminary findings) at the British Small Animal Veterinary Association’s annual Congress. Whilst the live event was an early casualty to the COVID19 lockdown, the abstract session was moved on-line in May, reaching a virtual audience of over 160 veterinary professionals from around the world.

The first abstract summarised our first study using the VetCompass TM database, reviewing the anonymised veterinary records of over 900,000 UK dogs to explore canine risk factors for heat-related illness. This abstract can be downloaded in text form below, or you can watch a recording of the presentation.

The second abstract explored the “triggers” for heat-related illness in UK dogs, reporting the most common reasons dogs develop heatstroke, and which reasons had the highest risk of causing death. This abstract can be downloaded in text form below, we hope to be able to share the video soon.

Video coming soon!

Findings from our VetCompass study will be published 18th June at 4pm!

Finally, our first Hot Dogs VetCompass study will be published TOMORROW AFTERNOON, where we report the incidence, fatality rate and canine risk factors for heat-related illness in UK dogs (the full paper of the first abstract). Thanks to a Dogs Trust Canine Welfare Grant this paper is Open Access, meaning you will be able to read the full version for free just as soon as it is published!

Watch this space for updates, we’re hoping it’s going to be a busy summer sharing our research, to help you make safer choices for your dog.

Getting hot under the collar – allowing your dog to pull on a collar and lead could be causing damage and increase their risk of heatstroke.

You only need to step inside a pet shop to see the vast array of collars, harnesses and leads available to dog owners. Owners can choose a particular look, colour scheme and material type. But amongst all of this, there is a more serious question of the role of the collar and the impact it may have on the dog. Historically, collars were used as a means of identifying a dog as being owned. Today, in the UK, as in many countries, it is a legal requirement for a dog to wear a collar and tag to provide key information about the dog, in order to identify the owner and to return it should it become lost. However, collars are now commonly used as a means of restraint and control for dogs to make sure they don’t wander off when out for a walk.

choc lab in collar

The problem is that the neck is a pretty sensitive area of the body, and many dogs pull on the lead. Ultimately, the neck connects the head to the rest of the body, carrying some pretty vital anatomical features such as the spinal cord, major blood vessels, the windpipe and the food pipe. Serious damage to the spinal cord in the neck can result in paralysis, or even death. Similarly, damage to the windpipe can impact a dog’s ability to breath or even result in choking, another potentially fatal injury. Linking to our normal research area, heat-related illness, compression of the windpipe can impact a dog’s ability to breathe effectively, impairing their ability to cool. When it’s hot outside, allowing a dog to pull on a collar and lead could potentially result in them over heating more quickly.

Sport_bulldog (2)

In fact, when questioned, almost 50% of owners suggested that their dogs pulled on the lead. This might range from a consistent light pull, to an owner being ’towed’ up the street by an overzealous dog. And of course, there is the sudden jerk on the lead from a normally calm dog, as a cat goes running across the road. On the other end of the lead is the owner, perhaps getting a little impatient at the 17th lamppost being sniffed, and offering a quick tug on the lead, or the frustrated individual jerking the lead to remind their dog to listen and behave. In all these instances, the resulting impact is a pressure applied to the dogs’ neck.

Two aspects are worth exploring; the impact of the type of collar – are some better than others? And the impact of the force applied – is a light pull on the lead less likely to cause harm?

loose lead walking (002)

Anne has been exploring just this topic, using pressure sensors attached to various styles of collar to test how much force then could be applying to our dog’s necks. Because of the risk to the dogs’ neck, and to retain consistency, a model neck (plastic pipe) was used instead of actual dogs. Working with Dr Mandy Roshier and Prof Donal McNally from the University of Nottingham, eight different collar types were tested. These were chosen to represent the range of commercially available types rather than focusing on specific brands: a rope slip lead, leather and thread, plain webbing, webbing padded with neoprene, thicker neoprene padded sports, wide lurcher, rolled collar and check chain.

The forces tested aimed to replicate a light pull on the lead (40N), a strong pull on the lead (70N) and a lead jerk (~141N).

The collars reacted differently in both the way the pressure was distributed and the amount of pressure applied to the model neck, the pressure increased as the force applied to the collar increased. Arguably the most interesting and valuable finding was that the pressure exerted on the neck model ranged from the lowest, 83kPa at 40N to the highest, 832kPa at 70N across the range of collars. To put this into context, in humans, pressure over 33.3 kPa has been shown to increase intraocular pressure (pressure within the eyeball which can lead to pain and ultimately blindness) and compress blood vessels, limiting blood supply to tissues. Tourniquets used in emergency situations to stop serious blood loss following trauma are used at a pressure of 33.3kPa on the arm and 40.0kPa on the thigh. In horses, pressures above 30kPa under the saddle are associated with back pain.

30kPa is enough pressure to strangle a human, and 230kPa is enough pressure to crush a human’s windpipe.

In short, no single collar tested provided a pressure anywhere near low enough to remove the potential risk of injury when pulling on the lead. Where dogs pull on the lead or the lead is jerked, there is a risk of injury to the neck for all collar types and styles tested, even where collars are padded or wide fitting. Collars are a great way to display tags and add a little personal flare to your dog. But for restraint and control, a non-restrictive harness is a much better option, and in hot weather a harness is definitely the safest option.

The full article is available here as a pre-print copy: FINAL Canine collars – an investigation of collar type and the forces applied to a simulated neck model

dogs-on-a-walk

Dogs in hot cars, why such a problem?

The problems with cars…

The average car is a metal box with glass windows. Metal is an excellent conductor of heat, meaning heat can pass through metal easily, think of your kitchen saucepans. Glass is a poor heat conductor but allows sunlight to pass through. This means that light energy from the sunlight enters the car through the windows but then gets trapped as heat by the glass. Some of this heat will be lost through radiation and conduction into the surrounding air, but if sunlight continues to fall on the car, it will continue to heat and in summer, this happens far quicker than heat can be lost to the environment; the reason greenhouses are so effective.  The net result is your classic summer hot car.

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The typical British summer is an unpredictable affair. Whilst temperatures regularly reach 20oC or more, often we have consistent cloud cover, intermittent rain or high winds to keep things feeling fresh, and stop cars turning into ovens.  Last summer, we experienced one of the first prolonged heatwaves of this century, with temperatures regularly hitting 30oC and endless blue, cloudless skies.  We have become complacent. Our dogs are typically part of our family, so we like to take them with us, whether we are taking them for a walk, for a day out, or travelling somewhere. The problem is, on a typical sunny day of 21oC, your average family car will reach temperatures of 31oC in 10 min. As the outside temperature climes to 31°C, the internal temperature of the car can reach 54°C. 80% of that temperature rise happens in the first 30 minutes.

We’ve all seen the adverts, surely no one would be so stupid…?

Since 2016, summer has been heralded by the “dogs die in hot cars” campaigns supported by a number of charities to increase awareness of the risk of leaving dogs in cars in the summer, and yet last year (2018) the RSPCA received 8290 calls, an increase from around 7800 calls concerning heat exposure in animals 2017. In a single weekend, over the 2018 May Bank holiday weekend, 217 calls were made by people concerned about dogs left in hot cars. One London police force was even offering a ‘free ventilation service’ if dogs were left in cars during the hot weather (by breaking the window).

car window

So why do people leave dogs in hot cars? A two-minute trip into the shop for a couple of forgotten items can easily become ten minutes. When questioned, owners gave a range of excuses, from “My dog is white, he’ll be fine” to “We feel bad leaving him at home on his own all day.” “We didn’t think we’d be long.” “It’s OK, I’m a vet”. No doubt, the vast majority of people do not want to harm their dog, but simply do not think. When leaving the car, the air con or open windows from travelling can make the car feel relatively cool. However, left in the sun for any length of time, even with the windows cracked slightly, it will get hot. Shade can help to keep the car cooler, but as the sun moves round, the shade can quickly disappear.

A human in a similar situation would begin to sweat to try and lose heat. Dogs don’t have the ability to sweat, they will pant, but as the temperature continues to rise, panting becomes less effective, and once the car temperature exceeds body temperature (around 38oC) there is nothing the dog can do to cool down. Unless the dog is actively cooled (see below) their body temperature will rise with the car temperature, and once they exceed 41oC, they are likely to develop heatstroke.

Heatstroke – the problem

Heatstroke isn’t the same thing as sun stroke, or heat cramps, or heat exhaustion.  These conditions can often be treated with cooling, plenty of fluids and rest. True heatstroke causes multi-organ failure. Picture an egg in a frying pan, you crack the egg, the yolk is yellow but the egg white is clear and jelly like.  Once the egg starts to heat, the chemical structures of the proteins start to change, the egg white becomes firm and changes colour. Now imagine this happening to the proteins within the body. As body temperature exceeds 41oC the stomach and intestines stop functioning, so the dog may vomit or pass bloody diarrhoea. The kidneys stop working, so despite fluid therapy the dog is unable to flush out the toxins from all the cellular damage taking place around the body. If the dog’s brain overheats, they may start fitting, or fall into a coma. The mortality rate for dogs with heatstroke is up to 63%.

Don’t risk it.

Don’t keep your dog in the car and never leave them unattended. Even in the shade, car temperatures can increase quickly, and shade may disappear. Leaving windows partially open has little effect on car temperature. If you are stuck in traffic or travelling, have the air conditioning on to keep the car cool and make sure windows are shaded from direct sunlight. Don’t assume your dog in the car boot area is fine because you are, check them regularly, your air conditioning may not reach the boot. Ideally, leave your dog at home in hot weather. Car shields and shades may help to keep the car cool by reflecting the sun’s rays, but some may also act as an insulator, particularly if the car is already hot inside. If you have no alternative other than to keep your dog in the car, open all windows, open the boot, try and maintain airflow, park in shade, and don’t leave your dog. Stay with them so you can be absolutely sure they are OK.

dog car

If you see a dog in a hot car, the advice is to phone the police. Heatstroke can kill quickly. A dog that is suffering from heatstroke needs to be actively cooled and taken to the vets. Active cooling is key. Even before setting off to the vets, use water to splash the dog’s legs, belly and throat area, get them out of the sun and into the shade, and if possible move them somewhere with good air flow – this might be in a car with the air conditioning already blowing. To give you an idea, the army have been known to use the downdraft from helicopter rotor blades to create airflow over soldiers with heatstroke. Next, getting to the vets as quickly as possible is the current best advice. Avoid using ice or very cold water, as this can do more harm. When your skin is cold, the blood vessels constrict, which can make it harder to cool the dog, and increase the risk of them going into circulatory collapse (shock).

There is no guarantee any dog will survive heatstroke, so the best way to keep your dog safe is to prevent it.

What is a “normal” body temperature?

If you’ve read any of our posts so far you will know we are all about monitoring body temperature, specifically as a means of understanding heatstroke risk in exercising dogs. As our fabulous friend Dr Jackie Boyd likes to remind dog owners:

You cannot manage what you do not measure and monitor.”

Whilst Dr Boyd is referring to measuring food in relation to canine nutrition and weight management, the same applies to body temperature. You can only be sure your dog is not over heating if you measure their body temperature. You can only be sure your temperature management strategy is working if you continue to monitor their temperature. We’ve previously shared some advice on methods of monitoring body temperature in dogs and other animals, and we have an update coming on this topic very soon! Crucially though, if you’re going to measure your animal’s temperature, you need to know what the numbers mean, and how to react appropriately.

The “normal” range

For almost every measurable aspect of an animal, from age, height and weight, to temperature, heart rate or urine production, there are “normal” reference ranges. In theory, these are statistically calculated limits of the normal population; in other words, 95% of healthy animals will fall within this range – there are always extremes that don’t fit the normal limits.

light-sepia-household-thermometer-166493

Google “normal temperature for a human” and you will see the top result, Wikipedia, reports “The normal human body temperature is often stated as 36.5–37.5°C”. It goes on to mention that “In adults a review of the literature has found a wider range of 33.2–38.2°C (91.8–100.8°F) for normal temperatures, depending on the gender and location measured.” A study recently found that the long established “normal” body temperature for humans is too high, highlighting the continued use of out of date normal ranges by medical professionals all over the world. This situation is mirrored in animal species. Textbooks state the normal range for various biological parameters in almost every species, but rarely state where this reference range has come from, how old it is, which animals were used to establish it and how their temperature was measured.

Our primary interest is canine health and welfare, so this all started when we tried to find a reliable source stating the normal resting temperature for a healthy dog. We struggled. Every textbook listed a slightly different range, 37.9-39.9°C on one website, then 38.2-39.2°C in a veterinary nursing textbook. The most recent reference we found was in a paper measuring rectal temperature in 62 dogs presenting to a veterinary hospital for routine health checks, who reported a normal range of 37.2 to 39.2°C. However, this did not report how this range was calculated, so without details of the statistical methods used to determine this range, it can not be considered truly valid.

Where does this leave us? Well, at the moment, we don’t actually have a robust, recent, reliable normal reference range for canine body temperature, when measured with a rectal thermometer. Three different sources state that 39.2°C should be considered the upper limit of normal, so we are fairly happy to accept that as our upper limit. What we do have, is a scientifically calculated normal reference range for canine ear temperature – because we calculated it! We measured ear temperature 416 times, from 157 healthy dogs attending various canine sports events over a two year period. Importantly, these dogs were not at the vets, so whilst they may have been excited, they were not stressed or scared. We calculated the normal range to be 36.6-38.8°C.

FINAL Establishing a reference range for normal canine TMT (you can read our published study here in the un-formatted version)

download
37.2 to 39.2°C is the current best estimate for normal rectal temperature in dogs.

Returning to rectal temperature, we know from our research, and from studies done by various other research teams around the world (Zanghi, 2016; Gomart et al., 2014), that ear temperature tends to measure around 0.4-0.6°C lower than rectal temperature. So, the rectal range of 37.2 to 39.2°C then quite nicely reflects our ear temperature reference range, just 0.4-0.6°C higher. This is the range we would consider to be most appropriate for interpreting canine body temperature, when measured with a rectal thermometer.

Equine body temperature

horse legs

Because we are both slightly mad, some might say obsessive, we couldn’t stop at establishing a normal reference range in just dogs. Oh no, we had to look at horses too. Whereas a dog may try to escape, sit down, or worst case scenario bite should they resent having their rectal temperature measured, a horse can, and if suitably aggrieved will kick you. This can be catastrophic. So if you’re going to risk your life measuring your horse’s temperature, and there are plenty of reasons you should be doing this, we felt it our duty as scientists to ensure you have a means of accurately interpreting the result.

We started by trying to find the evidence behind the “normal temperature range” for horses. We failed miserably. Once again, whilst plenty of textbooks, websites and other studies investigating equine temperature all state what the normal temperature range for a horse is, none of them reported where this range came from. Similar to the situation in dogs, if you don’t know where a reference range came from – how many horses were included, what part of the world, what breeds of horse, who took their temperature, how was their temperature taken – how can you be certain it is relevant to your horse? The simple answer is, you can’t.

stabled horse

So we decided to establish our own reference range. The horses at our University Equestrian Centre are cherished; the team caring for them will (and have!) battle blizzards, tropical storms and heat waves to ensure these horses are fed, watered, comfortable and loved. Part of their routine husbandry includes temperature monitoring, and yes, being University horses they do have to work for their living, so they are often used in non-invasive research work like our study comparing rectal temperature to eye temperature (measured with a non-contact infra-red thermometer, and coming soon!). Working with Dr Carol Hall and Dr Anne Stevenson, we collated rectal temperatures taken from 41 of the horses on the yard, measured at rest during a number of projects and routine monitoring. This gave us over 600 resting, healthy horse temperatures, all measured with a digital rectal thermometer by a familiar person, in the comfort of their stable. Knowing the horses were relaxed and not stressed is important, as stress can influence temperature in horses and other species.

We used a statistical method to then determine our horse’s “normal” temperature range, basically the middle 95% of the temperature readings. On our yard, this was 36.0-38.0°C. The upper limit is particularly important, as it is around 0.5°C lower than most of the previously published normal temperature ranges for horses. When an animal’s temperature exceeds this upper limit of normal, they are considered to be hyperthermic, too hot. The temperature reading alone can not explain why the animal is too hot, but it is an important indicator that something isn’t quite right (or, the horse has been exercising or in a hot environment). The term pyrexia, or fever, describes an animal that is too hot due to illness, this could be an infection, inflammatory or painful process. A low grade fever is where an animal’s body temperature is just slightly increased above the normal range and can be an early indicator of disease. It is therefore important that the normal reference range is accurate, otherwise these early indicators of illness can go unnoticed.

It is worth noting again, that the method of temperature measurement used is really important to consider when assessing your animal’s health. True core body temperature can only be measured using invasive, or ingestible devices. Rectal temperature remains the most accurate estimate of core temperature in most animal species (thankfully in humans non-contact thermometers appear to be as reliable!), but even the depth of rectal thermometer probe placement can have an impact on the resulting reading. A difference of 1cm can impact the temperature reading in chinchillas, whilst inserting a probe to 15cm or deeper in horses is likely to result in a higher temperature reading being obtained. Whilst we have no published evidence to support our theory, we suspect inserting a rectal probe to 15cm or deeper may also increase your risk of being kicked, so our normal temperature range is based on a 5cm thermometer depth.

If you monitor body temperature in two different ways you will get two different results. We know ear temperature is typically 0.4-0.6°C lower than rectal temperature. So it is important that you use the same method of temperature measurement each time if you are going to monitor your animal for changes in body temperature. That said, if you are ever worried about your animal’s temperature, use a rectal thermometer as this is still the most reliable estimate of core body temperature. Also, see your vet. Both high and very low body temperatures can be fatal in all species, so if your animal is unwell DO NOT delay seeking veterinary treatment. 

Our equine paper is available to read and download (free!) on the publisher’s site until 8th March 2019:

Establishing a yard specific normal rectal temperature reference range for horses. 

After this time, if you do not have access to the Journal of Equine Veterinary Science, then you are of course welcome to read the full article in the unfinished form below (this is the accepted manuscript, just not formatted into the journal’s style).

Establishing a yard specific normal rectal range horses FINAL.

We are hoping to recruit horses from all around the world to our next equine temperature study, so watch this space for further details if you would like your horse to take part!

horse-sleeping

 

Hot Dogs – investigating the epidemiology of canine heatstroke presenting to UK primary care veterinary practices

The Hot Dog’s team (Emily and Anne) are now working with Dan O’Neill from the Royal Veterinary College on a UK wide canine heatstroke study. The study will use data from the Vet Compass™ database to review the clinical records of over 900,000 dogs registered with UK primary-care veterinary practices for heatstroke events. As well as canine risk factors (e.g. breed, age, sex and bodyweight), additional information will be collected to establish the incidence, fatality rate, seasonality and underlying causes for canine heatstroke. Understanding the risk factors of heatstroke specific to the UK dog population will provide evidence to better support educational campaigns aiming to reduce or prevent this potentially fatal condition.

This project has been funded by a Dogs Trust Canine Welfare Grant.

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The results of this (likely two year) project will be published in an open access journal, so the link will appear here on the Hot Dog’s site as soon as it is available!

hot stevie

Canine Activity Survey Links!

Thanks to some fabulous people we now have our activity survey available to complete in several different languages! If you know anyone with canine friends/family or businesses who speak the following languages please share 🙂

Deutsche (German):

An alle Hundebesitzer! Haben Sie 5 Minuten Zeit, um eine Umfrage über die Bewegungsgewohnheiten Ihres Hundes auszufüllen?

Español (Spanish)

Se convoca a todos los dueños de perros: ¿tienen 5 minutos para rellenar una encuesta sobre los hábitos de actividad de su perro?

Magyar (Hungarian):

Felhívás minden kutyatulajdonos részére: tudna szánni 5 percet arra, hogy a kutyája napi mozgástevékenységét felmérő kérdőívünket kitöltse?

Nederlands (Dutch):

Oproep aan alle hondenbezitters, kunt u 5 minuten vrij maken voor de activiteiten gewoontes van uw hond.

Português (Portuguese):

Chamando todos os proprietários de cães, você tem cinco minutos para completar um questionário sobre os hábitos de exercício do seu cão?

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The Wonder of Bone.

We recently attended an incredible talk by Dr Martin Fischer on the wonders of Dogs in Motion. This frankly blew our tiny minds. So we’d like to share some of the incredible work being done on bones and explain how this links with canine heatstroke.

Dog breeds and bones

It all comes down to the skull. Firstly, a bit of background on how selectively breeding dogs for skull shape impacts the skeleton as a whole.

Dogs with a shortened nose (brachycephalic breeds) often also have a shorter, squarer pelvis. This has a cascade effect. It impacts how they walk, which in turn impacts the forces on their leg bones, which impacts the shape of the long bones. Tall, slender dog breeds tend to walk with their legs underneath their body, like a model on a cat walk stepping one foot in front of the other. This is the most efficient method of moving if you are a dog. As soon as the dog becomes broader, the chest becomes more barrel shaped, the dog walks with the feet either directly underneath the shoulder joint, or, in very barrel chested dogs they may even walk with the feet wider than their body, like a cowboy. This is not an efficient way of moving, but may be necessary for fighting. Traditionally, selective breeding aimed to develop a dog with a purpose. Sight hounds were bred for speed to catch prey, bull breeds were developed for their jaw strength for fighting.

Two very different dogs

This altered skeleton structure also causes the legs to move differently. In a Greyhound or Whippet, the legs simply swing back and forth, like a pendulum. The bones grow in an elliptical shape as this provides the best strength to withstand the force of trotting, running, jumping and landing. This again is streamlined and efficient. In a barrel chested breed, the legs don’t just swing back and forth, they twist and rotate to provide the same stride length. This twisting and rotating causes the bone to grow in a perfect circle, which is less aerodynamic and reflects the less streamlined motion. This means a barrel chested dog, which includes almost all brachycephalic breeds, has to work harder to move the same distance as a non barrel chested breed. This increased work, requires increased effort, which generates more body heat from muscle activity. They also tire faster, meaning exhaustion occurs more quickly.

What do bones have to do with heatstroke?

Dogs only sweat on their paw pads, so they rely on their breathing for temperature regulation. A dog’s long muzzle (nose) is a key method of cooling. Inside these long muzzles, are the nasal turbinates (see below), as series of scroll like bones that are coated in tissue similar to the surface of the lips and gums. These nasal turbinates hugely increase the surface area within the muzzle. This means a huge area of wet tissue is available for air to pass over every time the dog inhales. This functions to trap particles and potentially dangerous microbes like bacteria within the mucous in the nostrils to reduce the risk of respiratory infections. But most importantly, passing cool air over a wet tissue, allows evaporation and cooling.

Dog skull cross section

Dogs with a short muzzle, have a smaller area available for air to cool within the nasal turbinates. If the dog with a short muzzle also suffers from brachycephalic obstructive airway disorder (BOAS), they also have smaller nostrils, so the air cannot flow into the nasal turbinates as quickly. They then have narrowed air passages in the throat and whole windpipe, meaning both inhalation and exhalation is slower, and requires more effort. Remember these dogs are also using more effort and energy to move their limbs than a normal dog, add to that increased heat generated by the respiratory muscles having to work harder too.

Nose length comparison
Compare the length of the muzzle on the two skulls. The brachycephlic breed on the left has a much shorter muzzle, so significantly less surface area of nasal turbinates for cooling.

So, not only do brachycephalic breeds over-heat more quickly because simply walking and trotting they use more energy than a longer legged, longer nosed dog, but they also have a significantly less effective cooling mechanism because of their short nose. At the talk by Dr Fischer we were told that in Germany, Bulldog owners are advised to actively cool their dog as soon as ambient temperature exceeds 25oC. French Bulldog owners are advised to actively cool their dog above 28oC.

Altering bone, alters a dog’s risk of developing heat stroke.

Bone and insulation

The wonders of bone continue. People often think of a bone as a permanent, fairly fixed body structure. You suffer growing pains during adolescence whilst your skeleton grows and develops, then you reach your adult size and that’s about it. However, bone is continually growing, developing and changing right up until you reach middle age. Bone reacts to the stresses placed upon it. If you do a lot of high impact activity like aerobics, running, jumping or cross fitness, your bone responds to this by strengthening and changing in structure. If you are, as Dr Fischer put it, a “sofa pumpkin” (aka a couch potato, but we MUCH prefer this term!) and subject your bone to very little strain and load, bone will become less dense as you age.

sofa dog

How does this affect body insulation? Active bone, releases a hormone called osteocalcin. This hormone alters how cells respond to insulin in both mice, and humans. A failure to respond to insulin causes type 2 diabetes mellitus. In humans this condition is associated with a sedentary lifestyle, excess intake of carbohydrates and obesity. Mice with no osteocalcin are more likely to develop both type 2 diabetes and obesity. Mice with high levels of osteocalcin are almost resistant to developing type 2 diabetes and obesity. The link between a sedentary lifestyle and an increased risk of both obesity and diabetes mellitus type 2 is partly due to bone.

So, a dog doing very little high intensity exercise that involves stressing and loading the bone (just walking and mainly being a ‘sofa pumpkin’) is at greater risk of becoming obese and developing type 2 diabetes. The obesity is a big problem. An increased layer of fat under the skin acts as insulation, so the dog loses less heat into the surrounding air. This means the dog needs less energy to maintain body temperature (dogs typically use around 70% of their energy intake from food just to maintain their body temperature, this increases if the dog is in a cold environment). So if their diet remains the same, they will be consuming too many calories for simply maintaining their body, so the excess energy will be stored as, you guessed it, more fat. This becomes a vicious cycle.

Sofa Pumpkin

Whilst dogs lose heat through their respiratory tract, in particular using their nasal turbinates, they also lose heat through conduction and convection into the air and the floor in contact with their skin. If they are overweight the extra fat beneath the skin reduces this heat loss. These dogs are then heavily reliant on using their respiratory tract to cool, so you might notice they pant more than a less overweight dog, at lower ambient temperatures. Obese dogs are at increased risk of heatstroke, and are more likely to die from the condition.

How do bones impact activity?

Anyone who has ever experienced osteoarthritis or a fractured bone will know the answer to this question all too well. A painful joint or bone is horribly unpleasant, so we avoid using it. Not using a bone, especially a bone in the leg, will impact loading on that bone. This impacts bone strength, the release of osteocalcin, and also the health of cartilage that lines our bones in joints. Cartilage relies on loading to supply nutrients to the deeper layers, no nutrients, the cartilage thins and calcifies into new, abnormal bone. This contributes to osteoarthritis development.

So the less you use your bones, the weaker they become, and the more likely it is that you will develop painful joint disease. This makes you less inclined to use your bones, because they are painful. Which starts the cycle all over again.

So what should we do?

Body composition and skeletal health is hugely important for your dog’s overall health and welfare. Musculoskeletal disorders, including osteoarthritis, are among the top three causes of death in dogs, alongside cancer and neurological  problems.

Look critically at your dog. Can you see their ribs or can you feel them? If not, your dog could probably lose some weight. This will also allow them to be more flexible and active. Being more active, will prolong their bone and joint health. Ultimately, this will reduce their risk of heatstroke.

If the wonder of bones has gripped you as much as it did us, we thoroughly recommend Dr Fischer’s book, Dogs in Motion. A sneak preview in the video below.

Dog’s in motion (opens video in new window)

 

Cold as ice: Keeping hot dogs cool.

The heatwaves currently sweeping the UK, Canada and Japan this year have already resulted in the loss of both human and canine lives. The UK’s Environmental Audit Committee warns the frequency of such heatwaves is likely to increase in the UK , with the number of human deaths potentially increasing three fold. We have been warned that society needs to be “better prepared” for such heat, so here at Hot Dogs Canine Research we’re starting now!

Firstly, some “false news”

Ice cubes are not dangerous to dogs, provided they are used appropriately. There has been a lot of misinformation on social media regarding ice cubes, with a recent story suggesting that a vet warned owners ice cubes could kill their dog. This story has been misinterpreted. A dog with heatstroke should not be cooled with ice. We’ll come on to why later in the post. A dog in a heatwave, getting fed up with the hot weather, can absolutely have the odd ice cube. Or iced dog food popsicle, or frozen cream cheese lick mat! A fit and healthy dog, will not suffer any ill effects from consuming frozen food or ice cubes, in the same way that we suffer no ill effects from ice lollies. They should be provided in moderation, and they should not replace constant access to clean, fresh, cool water.

Cooling a playful dog

If you have a dog that is a little too stupid to realise it is too hot to play (see Stevie below for a classic example), you should consider active cooling methods to stop them overheating. Stevie is partial to a hosepipe. He gets to play in the jet of water for a couple of minutes, then the hose is switched off. Dogs have died from water poisoning, so it is important to not encourage your dog to drink excessively when it is hot. Avoid lots of toy chasing/retrieving, or allowing dogs to snap at running water for prolonged periods. Stevie gets a couple of minutes, then the hose is switched off – moderation is the key.

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Swimming or sitting in water is also a great way of keeping cool. Dog proof paddling pools are great – the inflatable ones often succumb to punctures from claws – and some dogs will choose to just climb in and lie down. Swimming in open water is not only a great way to cool down, but also excellent exercise for hot dogs. Sadly during summer blooms of blue-green algae can render small lakes and ponds dangerous to dogs, so keep an eye out for warning signs and learn how to recognise the problem here.

Cooling coats and mats are becoming increasingly popular, but be aware there is no robust evidence to support their use, yet. We are in the process of evaluating one, so watch this space for updates!

Cooling a hot dog

If your dog is hot from exercise, you may want to consider actively cooling them on a regular basis. Dogs do not sweat (apart from their paws) so they rely on panting, and losing heat from their body through radiation into the environment, or conduction to colder surface or liquid.  There is some evidence that dogs may continue to overheat AFTER they have finished exercising – our study investigating cooling in dogs supports this finding in canicross dogs – so the risk of heatstroke doesn’t end just because the exercise had.

There is very little robust scientific evidence to support any specific cooling method.

Studies have been done cooling dogs with heatstroke, but none to date simply cooling dogs post exercise. Our advice at the moment, is to first know your dog and trust them. If they are dragging you to the nearest puddle, lake or water bucket, chances are they are looking to cool themselves down. Let them. Most dogs will get out when they’re comfortable.img_1733

If like Murphy here (on the paddle board), your dog likens water to a dog eating monster, you may struggle to get them into a paddling pool or stream for a quick dip. Applying water with spray bottle, or sponge to the legs, inner thighs, belly and neck is the next best advice. Dogs with a heavy coat and become water logged, and can take an age to dry, so targeting the areas with less hair, like the belly and thighs, can provide some relief, without causing too much of a wet dog smell.

Murph on a paddleboard

Allowing your dog to drink is incredibly important. Dehydrated dogs get hotter when exercising , and are at greater risk of heatstroke. If your dog has been unwell, especially with diarrhoea or vomiting, they are more likely to be dehydrated, so ideally don’t allow them to exercise until they are fully recovered. Allowing your dog to drink tap water (typically between 10-15oC depending on the time of year) will help them to cool, and maintain hydration. Again you need to know your dog. If they are likely to drink a 2 litre bowl dry in one sitting and ask for more, you may need to stagger their intake, but most dogs will drink as needed.

Cooling a dog with heatstroke

Again, there have been several stories on social media regarding cooling dogs with heatstroke, very few backed by up solid science.

What we do know, comes from the dark days of science well before the Animals in Scientific Procedures Act 1986 legislation. Dogs were heated to the point of collapse, or unconsciousness. This study found that comatose dogs cool differently and much slower than conscious dogs with heatstroke. We know that dogs presenting to vets in a coma tend to have a poor prognosis for survival, likely due in part to their inability to effectively cool.

A conscious dog with heatstroke was found to cool quickest when immersed in water at 15-16oC. These dogs climbed out of the water baths themselves once they had recovered.

Stevie in the lake

The comatose dogs cooled much slower than the conscious dogs, largely because they stopped panting. Their rate of cooling was similar in water temperatures ranging from 1 to 16oC, however, two of the dogs cooled with ice water died immediately following immersion in the water. These dogs started shivering once they were place in the ice water bath, which could have caused further elevation in body temperature contributing to their deaths. When placed in water above 18 degrees, the dogs cooled more slowly.

In an emergency situation, the current best available advice for treating heatstroke is to continuously pour tap water over the dog, with as much air movement as possible, a fan or air conditioning is ideal. Do not delay getting the dog to a vet, especially if they are already comatose. These dogs need emergency care to maintain their blood pressure and try to save their brain, kidney and liver function. Cool the dog quickly, then transport them whilst maintaining air flow (windows down or air con on in the car) to the nearest available vet.  Try not to lay things over the dog, like wet towels, as this could restrict air flow to the skin and could reduce heat loss.

The single most effective way to ensure a dog’s survival, is to prevent heatstroke from happening.

Once heatstroke has occurred, rapid action is required. If the dog is still conscious, allow them to drink a little, and cool them with tap water. Seek veterinary care quickly. If the dog has already lost consciousness, every single second counts. Rapid cooling, then ideally continue cooling on route to the vet.

If its hot outside, chill out! Lie back, put your feet up, and enjoy a nap like Monty here.

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