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Posted 15th February 2021

It’s fair to say that every yard across Dorset and The New Forest has their own opinion on when and how to rug their horses. With so many different viewpoints it can be difficult as a horse owner, and as vets to accurately advise clients.

We consider each horse to be different; what works for one horse may not work for another, but we cannot deny that many horses and ponies can live without a rug all year round. As a mammal; The Horse has evolved exceptionally well to maintain their core body temperature regardless of the outside air temperature. Quite often, we are guilty of adding an extra rug because we feel cold, not necessarily our horses.

We have discussed previously that not rugging your horse over the colder winter months can aid in weight loss. If you are currently looking at your horse thinking he could do with losing a few kilos think about taking that rug off now whilst the weather and grazing is still on your side.

But what if my horse is cold? 

Horses use thermoregulation to maintain their internal body temperature. Some elderly horses, and those lighter breeds may need a little extra help when the weather turns, but a horse in good condition will normally fair well turned out “naked”. The thick fluffy coat your horse grows heading into winter is an effective insulator, those horses used to colder temperatures will grow an impressively thick coat. This thick hair is covered in a natural grease; that white stuff you will often see on the inside of your rugs, or under your saddle pad. This grease repels water, preventing your horses skin from getting wet and helping them keep warm on the cold wet days we see in the South West. No matter how drenched you think your horse’s coat is, feel through it to the skin, it’s very likely to still be dry and warm. That nice thick coat is not only waterproof, it’s also adaptive! Thanks to pile erector muscles, the hair is able to stand on end when its really cold, trapping the warm air between the hair and the skin making your pony twice its normal size on cold days.

Interestingly, horses don’t wait for it to be cold before growing their winter coat. As the days grow shorter they instinctively know that cold weather is on its way. Their bodies naturally begin to adapt ready for winter, then on the other side, as the days get longer and we see more daylight, they shed their winter coats ready for spring.

Don’t worry though, they’re not just relying on that thick winter coat to keep them warm. The digestive process of breaking down long fibres produces heat through contractions of the hind gut; as well as the associated blood flow. Heating from the inside out is more effective than fighting the outside air temperature, therefore access to forage is often more important than a thicker rug. As horses graze for around 19 hours a day, they are more than capable of keeping themselves warm through these digestive processes. As we know, grazing promotes movement, allowing the muscles to also generate heat, we often find our horses are friskier on the colder days, and they will sometime use play to keep warm. Fat is of course, a natural insulator and can affect the growth of a winter coat. It is natural for a horse to gain weight over the summer months, only to lose it again through the winter. However, those domestic horses who are leaving winter overweight, and never actually losing that weight are often prevented from growing such an efficient coat. Thereby actually making them colder to enable their natural processes to aid weight loss. So by allowing our horses to lose weight over the winter months we are promoting their natural ability to keep warm.

Not only have our horses adapted physically, they have developed behaviours to help them survive the winter months. They can easily adopt the stance of turning their backs to the wind and rain, providing protection for their heads, necks, eyes east and belly. You may even notice they are hanging around together more as they share body heat amongst the herd. The frost you see on your horses back is a perfect example of how well they are insulated. If any of that body heat was escaping that frost would melt. Their thick coats keep the warmth next to their skin, instead of expelling into the environment.

Over-rugging a horse can cause more issues than we realise. Rugging in general affects the natural stimuli to trigger thermoregulation mechanisms. Those hair erector muscles need to exercise in order to work well, if our horses stop feeling even a little cold, those muscles aren’t getting used. Horses are designed to warm up really quickly, however they take a lot longer to cool down. Over-rugging makes it difficult for your horse to find a naturally comfortable temperature, as well as reducing their need to use up those fat reserves. So that rug may not only be making your horse colder, but also affecting his natural weight control systems.

As with every animal however, there are exceptions! Those thoroughbreds, elderly or unwell horses and stabled horses who have been clipped may benefit from the addition of a rug, but before you reach for that rug, think about who’s sake you are rugging for!

Overrugging and obesity has become more about owner perception rather than what our horses actually need. We are all guilty of anthropomorphising our animals, but we need to consider how our human intervention is effecting the health of our horses.