A more scientific approach to rugging horses

Some new research that may help with a more scientific approach to rugging horses to promote good welfare, but as yet, there’s no blanket rule:

Kim Hodgess, MSc student from Duchy College, UK has conducted preliminary research to investigate the effect of different rugs on the horse’s surface body temperature.

With British weather being very variable at the moment (and always) with near freezing temperatures overnight, followed by sunny warm days, followed by mild but wet weather, it can be hard to decide what rugs to put your horse in. I especially hear owners worrying if they are out at work all day and can’t be changing rugs each time the forecast changes.

Because most of us are susceptible to feeling the cold, it’s easy to assume our horses feel as we do, but this new research suggests that a lot of horses are probably wearing rugs unnecessarily and that this may actually be compromising their welfare.

Did you know just how different your horse’s experience of temperature is to our own? The thermoneutral zone is the range of environmental temperatures in which a healthy adult can maintain normal (comfortable) body temperature without needing to use energy above their basal metabolic rate.

The thermoneutral zone of a (naked) human is cited as being 25-30 degrees celcius. That means, below 25 degrees, we may be uncomfortable without enough clothes. For horses in mild climates, their thermoneutral zone is a vast 5-25 degrees.

So, apparently the only time we are ALL comfortable, naked, is at 25 degrees! Just one degree higher and horses may be struggling like we do when temperatures soar above 30.

Kim’s research suggests that even a light rug can have a significant effect on body surface temperature: fly rugs increased surface body temperature by 4 degrees, fleece rugs by 11 degrees, and light quilted rugs by 15.8 degrees!

When the ambient temperature was only 4-4.5 degrees, four of the lightly rugged horses in Kim’s study had potentially uncomfortable body surface temperatures of 24-30 degrees, compared with the un-rugged horses who maintained comfortable surface temperatures of 18.5-20.5 degrees.

So does this mean, any time we place even a light rug on our horses in temperatures above 10 degrees, that we are forcing them to be uncomfortably hot and interfering with their ability to thermoregulate? (10 degrees ambient temperature + 15.8 degrees added by rug = 25.8 degrees).

Is a rug only justified when temperatures drop below 10 degrees, and only necessary when temperatures are below 5?

Whilst much more research will be required to provide definitive evidence on when to rug, I think the above interpretation is a reasonable practical application for healthy adult horses in good body condition, who are stabled or have access to field shelters or excellent natural shelter.

In addition to shelter and rugs, feeding hay/haylage encourages fermentation in the hindgut and subsequent heat production.

What about clipped horses? Horses use their coat to trap air to insulate themselves, so when they are clipped we alter one of their methods of thermoregulating. I hope that future research will include clipped animals as well. Research in this area has already begun with regards to overweight animals – where there is evidence that clipping is a very effective means of causing weight loss.

On the flip side, how should we best manage thin horses? Is rugging them up on mild and warm days forcing them to use energy trying to thermoregulate that they could be investing in maintaining weight?

Of course, there are always individual horse factors to consider, as well as factors such as the ‘feels like’ temperature (useful information provided on the met office weather app) which may be a more appropriate guide than actual temperatures as they take into account windchill etc. I would always exercise more caution if it’s very wet, especially if it’s wet and windy, but being mindful that a light rug is often still going to be adequate.

Since I first read this research a few months ago, I have implemented it with my own three horses: My 27yo TB poor-doer is now only rugged when temperatures drop to 5-10 degrees, or when it’s wet, and she is maintaining weight better than usual. My 21yo TBX is only rugged when temperatures drop below 5 degrees. In prior years she has only worn a rug when it’s very wet and windy but due to other health issues I have decided to rug her when the temperature drops below 5 this year. My 21yo Welsh pony who is overweight never wears a rug. This will help him to lose weight over winter so that he does not have to be so severely restricted on his diet in summer.

It’s very important not to over-interpret results of studies that are not peer-reviewed and have not been thoroughly critiqued, so I certainly wouldn’t advocate relying purely on experimental figures to advise on how best to manage an individual feeling animal. But, the research provides some great thought-provoking research to help us think about rugging from our horses’ experience of temperature which is so different to our own, and to promote good welfare.

To read more about Kim’s research, visit the International Society for Equitation Science website.

Reference: Hodgess, K (Nov 18) ISES Media Releases: ‘To rug or not to rug?’

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Two ponies in rugs