How your horse stays warm

Always a topic that can lead to a heated conversation at this time of year is what rug to put on your horse. This is a difficult question to answer as all horses should be treated as individuals and it can be all too easy to be influenced by what other owners on the yard are doing or following the latest trends on rugs in the horse world.

In this blog Gillian Higgins explains just how clever your horse is at dealing with the cold and how this should influence how you rug him this winter, or if you need to rug him at all.

How your horse keeps warm

Horses don’t quite feel the cold like you do so just because you’re wearing a coat doesn’t mean you need to start rugging your horse.

“It has to be three times colder for horses to feel the cold as you do”

All warm-blooded mammals – that includes horses and humans, can tolerate a range of temperatures. Each species has a natural comfort zone - this is known as the 'energy-neutral range'. Horses cope best in dry temperatures between -9 and +15C. Essentially that’s when there are no bugs, no heat and no mud!

Your horse has a number of ways that he deals with the cold. Some of them you may have noticed him doing such as:

• Turning his back to the cold and fanning out his dock hairs. His rump and back have thicker skin and hair, and less surface blood vessels, and can withstand the wind better.

• Huddling with other horses to conserve heat.

• Moving about.

• Enjoying the winter sun.

• Seeking shelter - access to adequate shelter has been shown to reduce heat loss from wind chill by 20%. This can be a thick, high hedge, or a 3-sided field shelter.

There are also other clever ways that your horse is equipped to stay warm.

A large heavy digestive tract provides your horse with an efficient system of internal combustion! His hind gut contains millions of friendly bacteria and microorganisms which, can break down the insoluble carbohydrate and cellulose present in forage. Heat is a by-product of cellulose breakdown. One of the most natural, easy and efficient ways to help keep your horse warm in the winter is to ensure he has constant access to a fibrous diet and good quality hay.

Learn more about the anatomy of the digestive system at our online seminar: Digestive Anatomy Feeding and Nutrition

The skin is made up of two layers. The top epidermis which has several waterproof stratified layers and below this is the hypodermis, a loose layer of connective tissue in which insulating subcutaneous fat is stored.

Growing a winter coat. This coarse hair is set at an angle with a fine layer of softer downy hair beneath. This traps pockets of air to create an insulating layer, retain heat and act as an effective windbreak. The downward tilt of the coat deflects falling raindrops and snowflakes before they reach the skin. If the autumn is exceptionally warm autumn -like this year, or you rug your horse too soon this will reduce the length and thickness of his winter coat.

Oils in his coat act as a protective barrier and prevent the skin from getting wet. This is why your horse should not be bathed or over groomed, particularly if he lives out 24/7.

Piloerection is the erection of the hair due to contraction of the tiny muscles that elevate the hair follicles above the rest of the skin and move the hair vertically, giving the appearance of hair 'standing on end.' This increases the hair depth and traps air next to the body creating an insulating layer.

The blunt shape of your horse’s muzzle is richly supplied with blood so that he can withstand bitter cold without freezing. Also, thick eyelashes protect his eyes from wind and cold temperatures.

The anatomy of the lower limbs are very well adapted for coping with the cold. As there are no muscles below the knee the cells in the leg require less blood circulation, meaning they lose less heat. Whilst your toes are one of the first appendages to get cold, this is not a problem for your horse.

Thermoregulation - when the air around your horse is colder than his body temperature, heat transfers from him to the environment and he gets colder. The chief command centre for thermoregulation is thought to be the hypothalamus - a small but life-critical structure deep in the base of the brain. This sends signals via the central nervous system to take action to reduce the heat loss. Your horse does this by:

• Burning extra calories creates more internal body heat but this requires an increased intake of dietary energy. Without this your horse will utilise his body energy reserves (fat) and lose weight.

• Exercise – This produces heat from energy burned by muscles and is one reason that horses seem to run around more when the weather is cold.

• Shivering causes muscle contractions which raises your horse’s core temperature. As he has very large areas of muscle, shivering is an effective way of combating cold.

• Constriction of blood vessels. The uppermost layers of skin are covered with veins which circulate the blood close to the surface before returning it to the lungs. In hot weather, this is desirable, but when it’s cold heat loss must be minimised. This is achieved by blood being blocked from the veins close to the surface and rerouted into vessels which run deep under the skin, right next to arteries. This means the blood returning to the heart and lungs is warmed by the outgoing (countercurrent) arteries, preventing cold blood from penetrating the body.

• Conservation of energy and heat. Your horse can reduce the blood flow to extremities such as his ears, muzzle and legs. This is why you can assess his temperature by feeling his ears.

• Increasing Metabolism. This is achieved by sending nerve impulses to release neurotransmitters that raise blood pressure and heart rate stimulating the release of free fatty acids and the breakdown of glycogen. At the same time, the hypothalamus spurs the pituitary gland into action, ordering the release of large amounts of adrenocorticotropic hormone (ACTH) into the bloodstream. This triggers the production of cortisol, a steroid that increases the body's heat generating fat, carbohydrates and protein.

The role of rugs

With such a huge choice of rugs available is it any wonder deciding which rug your horse needs is confusing. The most important thing to remember is that your horse doesn’t feel the cold like you do. Also, every horse is an individual and some will cope better with cold weather than others.

The majority of horses in work are rugged because they are clipped and that is the correct thing to do. There’s also the practical consideration of using a rug to keep your horse clean and dry – especially if you’re riding after work. What weight rug you use comes down to a number of factors:

• Start with a lightweight rug and only move to a heavier weight one when the temperature drops.

• If your horse is in poor condition, old or young he will be more sensitive to the cold and using a warmer rug may be necessary. A horse with a good body condition will be well insulated, retain heat for long periods and repel the cold.

• The weather also has a big influence of how warm your horse stays - wind, rain and cold temperature lead to the greatest heat loss.

• What type of clip your horse has will impact what weight rug your horse needs – the more hair you remove the heavier the weight of rug your horse will need to keep warm.

• If your horse doesn’t have access to shelter, he will need a thicker rug as the temperature drops.

• If your horse isn’t clipped rugging flattens the hair and prevents piloerection.

If you do rug your horse, check and remove them regularly. If possible, on sunny days allow your horse to have some time - about an hour without a rug on - allowing him access to the sun will boost his vitamin D levels.

If you're still uncertain how to rug your horse take a look at this handy guide. Remember to consider all the other factors that have been mentioned here but this will help to give you a little more guidance.