For domestic horses the answer is yes, no, and maybe!
While it is true that wild and free-living horses survive without rugs, they move more than their domestic counterparts, are able to find their own shelter from bad weather and do not tend to live as long as domestic horses.
All horses should have access to shelter and, where they have good shelter, healthy younger horses do not always need to be rugged. Each horse is different though so treat each horse individually, with some being more likely to need extra warmth and protection than others. Older horses in particular may need extra warmth in cold and wet weather. Horses are very efficient at controlling their core body temperature, and in winter are effective at acclimatising to cooler temperatures. Unlike humans, normal digestion in the horse’s hindgut produces a large amount of heat and, therefore, owners may feel cold when their horses do not. Many people will feel their horse’s skin to gauge if they are warm, but this is not accurate and can lead to over-rugging, which can have negative effects on the horse’s health.
However some breeds of horses have a very fine skin and coat (such as Thoroughbreds and Standardbreds). This means that they feel the wet and cold more than tougher, hardier breeds of horse. There are always exceptions though so treat each horse individually. Care should be taken when rugging horses after exercise as immediate rugging will reduce the horse’s ability to dissipate heat, trap sweat and may increase the risk of rug sores, and fungal or bacterial infections on the skin .
Rugs must not be used as a substitute for shade and shelter (see the article Do I need to provide shade and shelter for my horse?). Horses should be given the freedom of choice to cope with changing weather conditions. This should include space for movement, protection from sunshine, rain and wind, dry bedding, and adequate access to feed .
What about rugs in summer?
When temperatures exceed 25°C, horses are at risk of heat stress . Using rugs on horses in summer can be a welfare issue. Rugs do not keep horses cool. A horse naturally has a sleek coat which reflects the sun and a horse will seek shade when they are hot as a natural response. Rugs prevent any cooling breeze from cooling the body. Also, horses are one of the few animals that rely on sweating to cool down and rugs impede this process (by preventing air from passing over the body, evaporating the sweat and cooling the body).
Many people rug horses in summer in order to prevent their coat from fading in the sun, however this is not advised as it may trap heat and reduce the horse’s ability to cool themself. Horses must be provided with access to shade (trees or shelter) during the heat of the day. This is especially important for horses who have white skin over areas such as the nostrils and, therefore, get sunburned easily.
Horses who suffer from Queensland Itch, which is an allergic reaction to midge bites, do need to be lightly rugged in summer to reduce insect bites.
What about rugs in winter?
In cold and wet weather a good quality and well-fitting rug can help the horse to maintain condition, as a cold, wet horse will burn a lot of energy keeping warm. Keep in mind though that if your horse is young and healthy but tends to get fat, rugs will actually help him or her to maintain that fat. In a natural situation excess body fat is burned off through the winter.
The coat of an unrugged horse stands up in cold weather to trap air and warm the horse. If you decide to rug you have to compensate for this mechanism as a rug will stop the hair from being able to do its job. In some circumstances a rugged horse is actually colder than an unrugged horse if it is a badly fitting thin rug that flattens the hair and reduces the movement of the horse without providing any real warmth. It is very important for horses to be provided with shelter and extra forage (e.g., hay), which also helps their digestive tract, rather than to use too many rugs in winter .
Rugs need to be checked regularly (at least twice a day) to make sure that the straps have not broken and the rug slipped, which can cause injury to your horse. If the temperature increases during the daytime and is warm (above 20°C) then it is important to remove heavy rugs, as the horse can experience problems with excess heat. Because a horse adapts to winter temperatures, their threshold for warmer temperatures is reduced and heat stress can occur and become a welfare issue.
Hoods should be used with great caution as they can slip and cover the horse’s eyes. If this happens, the horse can panic, and/or they may fall or injure themselves on objects they cannot see. In addition, a slipped hood can rub on the horse’s eyeball and cause an ulcer on the eye – a very serious condition for a horse requiring immediate veterinary attention. If a hood is used, the horse must be closely monitored while wearing it.
Rugs must be maintained to a high quality. If rugging horses in winter, owners must regularly check that the rugs are still waterproof. This is because wet rugs can be worse than no rug as they will increase heat loss from the body. Check the inner lining of rugs after rain to ensure they are still waterproof.
A rug should be removed regularly to make sure it is not rubbing, letting in water etc. and to make sure the horse hasn’t lost weight or gained too much weight. Rugs prevent horses from exfoliating their skin properly (by rolling and mutual grooming, etc.) so a rugged horse must be groomed thoroughly and frequently to get rid of the build-up of dead skin and hair (see the article Why do I need to groom my horse?).
If your horse is experiencing rug sores, read here for more information and helpful prevention strategies: How to avoid rug marks and sores – EQUUS
For more information please see the Equiculture Responsible Horse Care page.
 Hartmann E, Connysson M, Dahlborn K (2014) Effect of showers and blankets after exercise on heat dissipation in Swedish standardbred trotters. Equine Veterinary Journal 46: 12–13.
 Cecilie M et al (2020) Caring for the horse in a cold climate—reviewing principles for thermoregulation and horse preferences. Applied Animal Behaviour Science 231. https://doi.org/10.1016/j.applanim.2020.105071
 Padalino B, Loy J, Hawson L, Randle H (2019) Effects of a light-coloured cotton rug use on horse thermoregulation and behaviour indicators of stress. Journal of Veterinary Behaviour29:134-139.
 Rioja-Lang F et al (2020). Determining a welfare prioritization for horses using a delphi method. Animals 4:647.