Is my horse getting cold?
Surprising results from a sensor in my horse’s rug
There is an ongoing discussion in the horse community about whether to rug horses or not and if you do rug, whether we are over-rugging our horses. My horses are all rugged and kept out 24/7 in the mild but very wet winters in Ireland, and this is both for practicality, try getting caked wet mud off a horse before you ride them, and because I don’t like to think my horses are getting cold. But are they?
“Like humans, horses have a ‘thermoneutral zone’ (TNZ) — an optimal range of temperatures within which they can comfortably maintain their own body temperature. For adult horses in mild climates, this is between 5ºC and 25ºC. Humans, on the other hand, have a more limited TNZ of between 25ºC — 30ºC when naked. This means when humans feel cold, horses are still well within their comfortable zone. Humans often make decisions about rugging their horses based on whether they feel cold themselves, so they may well be using a rug on their horse when it really is not necessary.”
I am certainly guilty of rugging my horses based on whether I feel cold, so I’m curious to see if the horses are too warm or too cold under their rugs and as a horse technologist, I have the technology to find out!
Dragon was nominated to wear the first recording rug on the basis that she would be less likely to damage the rug than some of the others!
Dragon is a 15.2hh Irish Sport Horse with ⅝ Thoroughbred and ¼ Irish Draft and a splash of warmblood. She was chaser clipped in early October and by the time I started recording data in mid November the clip was already growing out. Although she looks more thoroughbred than draft, she is reasonably hardy and would not be the first horse to feel the cold.
Attaching the sensor
The data is recorded using a small, roughly 2cm round, data logger disc from BlueMeastro that was stitched into the lining of a new 50g rug from The Big Horse Shop, just in front of the hip bone.
Winter 20/21 was a great test with periods of below freezing for a number of days (pipe freezing weather) and more normal periods of rain and rain with wind. These temperatures are for nearby Sherkin Island on the coast, which is about 2.5 degrees C warmer than here. You can see the big blue downward spikes showing the exceptional cold periods in January and February.
My normal rugging regime has been to put a zero or 50g rug on in early October and then switch it to a 150/200g rug in late November/early December when the horses get a blanket or trace clip, so I was curious to see when the data suggested I needed a thicker rug.
But to my surprise, Dragon didn’t get cold (with one exception which we will come to!). While the temperature under the rug did dip down during the cold spells she showed no signs of discomfort, ears did not get cold, putting a hand under the rug felt cool but not cold. So I left the 50g rug on her.
Between mid November and the start of February, the ambient temperature ranged from -3.3℃ to 12℃ while the temperature under the rug went from 5.4℃ to 41.8℃!
As of January 2021, the results suggested that Dragon never got cold but that she did get hot when the sun came out on those cold clear days of winter. She never showed signs of sweating and I checked with my hand under the rug on a few of those rare sunny occasions. She also didn’t move to a shaded place so I’m guessing that she was not uncomfortably hot, but this needs further study.
And I was about to publish this information, when we had a few days of rain, sleet and a biting wind and finally she did get cold. So back to the data analysis to see if her getting cold could be seen in the data.
At 10am on the 12th of February when I checked the horses I found Dragon shivering and they were all standing hunched up sheltering from the cold easterly wind. She had been fine the evening before so I can’t tell at what point she started shivering so this red band may start earlier than I have drawn it. The rug was cold and wet on the outside but she was still dry underneath.
I put a second rug on and the weather was already improving so she quickly warmed up and went back to eating.
What is interesting is that from just the two temperature readings you cannot see that she was cold. The shivering probably increased the temperature under the rug so there was no big dip that might have been seen if she had got even colder.
What does not show from the temperature data is the wind chill and relentless rain/sleet, that was not heavy, but meant the horse’ heads and legs were cold for the previous two days.
Conclusion
This scatter plot of under rug temperature against ambient is colour coded to show the “rug off” events (pink), the hot events (orange) and the cold events (blue) in the middle of the chart. The correlation between the rug and ambient temperatures is clear in the green dots that show an upward trend, as the outside air gets warmer, the temperature under the rug gets warmer.
Dragon spent far more time too warm than too cold suggesting the 50g rug is the best default rug but occasionally additional rugging would be required to prevent her shivering.
So what will my new rugging regime be? Next winter I will stick with a 50g rug because putting on a warmer rug will mean Dragon spends even more time too warm, but I will boost this where we have a long running cold AND wet AND windy spell.
For this horse with this clip in this climate, a good quality 50g rug with a hood is a suitable rug for winter use in temperatures between -3℃ and +12℃ and may be suitable for lower and higher temperatures, but there is enough data to judge. However, for longer periods of cold + wet + windy weather, an additional 50g may be required.
What Next?
This is one horse in a new, good quality rug, kept outdoors in the mild conditions of Ireland. What if the horse was fully clipped? What if the horse was kept in? What if it was a thicker rug or an old rug that let in some rain.
This short trial has raised far more questions than it answers and I’m looking forward to adding a movement sensor that can detect shivering, running around and when the rug is off, intentionally or otherwise!
If you would like to carry out a similar trial there are some instructions here https://thehorsetechie.medium.com/diy-horse-rug-monitoring-b316725121a3 and can help answer any of these questions, please contact Phoebe Bright phoebe@horsetech.ie
A more technical version of this trial will follow soon…
