Horses have a wider thermoneutral zone than humans do. This means that when the temperature is between 5°C and 25°C1,2 a healthy horse can maintain their core temperature with minimal energy expenditure. If the temperature drops or rises above these parameters horses need to use their metabolism more to either warm themselves (see steps below) or cool themselves by sweating.
How horses naturally keep warm
When the environmental temperature drops below 5°C, the horse must produce more heat which may be done in several ways:
Horses will naturally turn their backs on wind and rain to protect themselves in poor weather. If in a group environment, they will also huddle closely to share their warmth.
Thick hedges and tree lines make great forms of natural shelter, or they may have access to a field shelter. Horses are more likely to feel the cold through a combination of persistent wind and rain. In these circumstances, having a good source of shelter will provide the most protection and help the horse stay warm.
Horses lose very little body heat through the air as their coat hairs stand on end, trapping heat and creating a layer of insulating body heat. You may have noticed horses with unmelted frost or snow on their backs, the reason this doesn’t melt is because the horse’s winter coat works by insulating them and not letting the heat escape.
Eating forage consistently throughout the day helps to keep the horse warm, acting as an in-built heating system by creating heat as the fibre is broken down in the digestive system.
Increasing metabolic rate
Horses will use more energy to keep themselves warm. This is a natural process throughout winter and allows any excess weight gained through the summer months to drop off as nature intended.
Do all horses need to wear a rug?
When considering rugging your horse, it is important not make this decision based on how you feel. Horses don’t feel the cold like we do and naturally grow a thick coat in winter to keep them warm. Their coat also produces natural oils to help keep them waterproof. Many horses, especially breeds such as the native pony and cob types, can adapt well to winter weather and easily cope without a rug when they have adequate forage and access to shelter.
Inappropriate rugging may cause the horse to sweat, resulting in irritation and rubbing and will prevent sunlight reaching the horse’s skin, limiting the production of vitamin D2. A deficiency can lead to reduced bone strength, however an hour a day exposure without a rug in bright, dry conditions, should be sufficient in minimising this risk.
Horses naturally lose weight during the winter months, but we can override this process by feeding them too much and over-rugging. This can result in the horse putting on excess weight all year round, which is worrying as weight gain increases risk of laminitis. Not rugging an overweight horse will help them lose weight naturally.
Try not to overgroom un-rugged horses as this may strip the coat of the natural oils and reduce its waterproofing abilities. If ridden, ensure any mud is removed from the areas where the tack is fitted to prevent rubbing and discomfort.
There are times where rugging may be necessary. Horses which are more likely to require a rug for additional warmth in bad weather include:
- Breeds that have a naturally thinner winter coat such as a thoroughbred or Arab
- Underweight horses as this will prevent them increasing their metabolic rate and using more energy to keep warm, leading to further weight loss
- Fully clipped horses are unable to use their coat for natural insolation, therefore it is important we compensate this my providing an appropriate rug
- Old or ill horses typically have more difficulty regulating their body heat. Older horses may also have difficulty maintaining their weight and experience an arthritic flare up from the cold and damp, which reduces movement and reduces the creation of body heat.
What to look out for when choosing a rug for your horse
Just like a pair of tights, the denier relates to how strong the outer fabric of your rug is. So, the higher the denier the stronger the material will be. If you have a horse or pony who is a world-class rug ripper, then a higher denier rug is the one for them!
The fill is used to describe the rug weight and can be categorised as:
- Light weight - 0g, 50g, 100g
- Medium weight - 150g, 200g, 250g
- Heavy weight - 300g plus
Why is it important to get the right weight rug?
Overrides natural insulation
If an inappropriate rug is used, it can override the horse’s natural process of insulation. As the hair is flattened, it is less efficient at trapping heat to insulate the horse’s body.
Increased stress on the horse
If a thick fill rug is used in inappropriate conditions, it will trap a lot of heat, which can radiate back to the horse’s body. As a result, the horse will be continuously trying to cool down which can place a lot of stress on the horse, causing them to sweat and making them uncomfortable. It is much easier for a horse to warm themselves up then it is to cool themselves down.
Don’t keep an overweight horse unnecessarily rugged through winter as this time of year can be used as an advantage to help the horse lose weight. Instead of un-used calories being laid down as excess fat, the horse can use the calories to keep warm.
Reduced body temperature
A 0g rain sheet can be a great choice in light rain, however, be conscious that in very poor weather, the rain is likely to seep through. When this happens, cold air meets heat from the horse’s body forming condensation under the rain sheet. As the lower temperature reaches the horse’s skin, their body temperature can reduce.
Choosing the right rug for your horse
When choosing the right rug for your horse, consider:
- Access to forage
- Feeding regime
- Horses body condition (fat score) /weight
- Is your horse clipped?
- Weather- is it just cold or cold, wet and windy? The wind chill factor can make a real difference!
- Access to shelter or a stable
- Level of work
- Time of year
How to fit a horse rug
If rugging your horse, it is vital that the rug fits correctly to limit any chance of rubbing or soreness. If we wear a pair of shoes that don’t fit correctly, they can become very uncomfortable, start to rub and create sores - it is very similar for our horses and their rugs! Watch our video below on how to correctly fit your horse’s rug.
Implications of ill-fitting rugs
If your horse wears a rug it is important to remove it daily so you can check for signs of rubbing or soreness and then refit or change as necessary. An ill-fitting rug or one left on for too long without checking may cause discomfort or even start to rub and cause injury as shown in the image below.
- Mejdell, C.M. et al (2020) Caring for the horse in a cold climate—Reviewing principles for thermoregulation and horse preferences. Applied Animal Behaviour Science. Vol 231.
- David Marlin - Rugging Round-up.