The reference ranges used to interpret body temperature in both humans and animals appear to be inaccurate. Here we share our latest research findings, this time on horses.

The full post is available here: What is a “normal” body temperature? — Hot Dogs – heatstroke education for dog owners



Equine body temperature

horse legs

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.


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 on the publisher’s site below, but does require a journal subscription:

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

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!



The Journey Begins

Thanks for joining us!

We are a group of researchers investigating equine health and welfare, with a particular interest in body temperature.

Our aim is to review, then potentially re-establish what is “normal” when measuring a healthy horse’s temperature.

We started by reviewing the temperatures taken from horses at our University Equestrian Centre. With over 600 readings from 41 horses, we established that the normal range of temperatures for our horses was 36.0-38.0°C. This is around half a degree lower than many of the reference ranges stated in textbooks or on websites.

This may not sound like a big difference, but this upper limit is often used to define fever and screen for infectious diseases such as shipping fever. If the limit being used to label horses as being at risk of carrying an infectious disease is too high, this could result in horses being misdiagnosed as healthy, putting bio security of yards at risk.


This is where we need your help.

We are asking anyone who owns a horse or a yard to share their horses’ temperatures. If you are monitoring your horse’s temperature routinely as part of bio security protocol, or for health monitoring reasons we would love to hear from you!

If your horse is:

  • at least 2 years old,

  • not on any long-term medication (apart from routine worming),

  • healthy, with no long-term of recurrent health problems (such as laminitis, respiratory disease or Cushing’s disease),

  • routinely temperature checked as part of their normal husbandry,

then we would like to invite you to take part in our project.

What will this involve?

We would need you to complete a consent form (below), stating that you agree to us using your horse’s temperature data for this project. You can either complete this consent form online, or e-mail it back to us. The form has a table to complete your horse’s details (age, sex, breed, colour, height) so that we can investigate if any of these factors influence a horse’s temperature. Please e-mail the completed consent form to you will then be sent a recording sheet and a link to an on-line submission option.

Horse Temp Owner Consent Form – Word document version to e-mail back (best for large numbers of horses).

On-line Horse Temp Owner Consent From – On-line version for up to 5 horses.

We need you to use a digital thermometer (see below), not a glass mercury thermometer to monitor your horse’s rectal temperature. It is important that this is a normal part of your horse’s routine, and you don’t start doing this just to take part in the study.

Measuring the rectal temperature of a horse

We need you to record the date, time, location (stable or field) and air temperature (using a weather app if you don’t have a thermometer on your yard) when you measure your horse’s temperature. We also need to know if your horse was wearing a rug, or had a wet coat. We need to know if your horse is vaccinated during the temperature monitoring period, including the type of vaccination given.

Then, we ask that you send us these details either by e-mail, using the template we will send you, or via a website link which we will send you upon receipt of your signed consent form. You can then submit as many or as few readings as you like. Every month would be ideal as we are interested in how temperature responds to changing seasons.

Our goal is to recruit horses from all across the UK (if possible around the world!), including as many different breeds and ages as possible. We will be collecting temperature throughout 2019 and 2020, with the goal of analysing the data and publishing the results in 2021.

If you would like to take part, please download the consent form below, and e-mail it back to

Horse Temp Owner Consent Form

If you have a large number of horses you may wish to download this extra document, it can be completed digitally and e-mailed back to the address above.

Extra horse details for large yards x10 horses

Or, complete the consent form on-line:

On-line Horse Temp Owner Consent Form

If you have any questions about the study, please get in touch using the site contact button or the same e-mail.

Thank you!