THE recent unpredictable weather is proving a guessing game for horse owners when the subject of rugging arises. With the winter months now upon us and the colder nights drawing in, the decision to fit a rug on our horses is a concern.
Horses are able to regulate their temperature, meaning they maintain their internal core body temperature at 37- 38oC, although foals, young stock and breeding stock have a slightly higher normal internal body temperature. This thermoregulation enables horses to thrive in all types of weather and climates.
How do horses maintain their body temperature during cold conditions?
The horse’s skin has a major role in the thermoregulatory process, as it protects against external temperature changes and heat loss in cold weather. The skin has the ability to act as insulation, depending on its thickness and condition of the animal. Fat is a very good natural insulator, therefore underweight horses with finer demeanour find it difficult to conserve heat in their bodies. In contrast, overweight animals find it harder to stay cool in hot weather due to the insulating effects of excess fat stores.
Horses can lose heat if the air temperature next to the skin is cooler than skin temperature. This is the reason why we often see horses standing close to each other in herds, as this method of positional sheltering regulates heat loss via radiation. This close arrangement to each other reduces the body surface area left exposed to the peripheral conditions.
The growth of equine hair during changes of season is controlled by photoperiod (day length). Changes in daylight hours are relayed by light receptors in the horse’s eye to the pineal gland in the brain. Darkness triggers the production of melatonin, which in turn stimulates hair growth, and vice versa happens in spring when days become longer and coats are shed. So, as winter develops, the horse is stimulated to grow a thicker, longer coat with native breeds being naturally hardier as they adapted to harsher conditions, making them better suited to winter conditions.
During unfavourable conditions, horses have the ability to enhance the thickness of the coat by means of hair piloerection. This is when the hair erector muscle raises, lowers or rotates in direction to protect the horse against poor weather conditions, as this process increases coat depth by 10% to 30% in adult horses. The horse’s coat is also naturally greasy, and acts as a water repellent against rain and snowy weather. The water runs off the outer hairs preventing the horse getting wet to the skin, therefore the longer the coat the more protection the horse has during the harsh weather. This can also be said for mud caked to their coats, therefore it is advised not to groom field kept horses on a regular basis during the winter.
The horse’s diet also has a major influence on its ability to maintain thermoregulation during the winter months. Horses are herbivores with diets mainly made up of carbohydrates found in forage and grass. The fermentation of fibrous carbohydrates in the horse’s hindgut produces substantial amounts of heat, which acts as the horse’s own central heating system. This fermentation process also generates increased blood flow, which supports internal core temperature.
Is rugging necessary?
The horse’s age, health, body condition, environment, hair coat and nutritional provision all influence the lower critical temperature of individual animals. When deciding if your horse requires a rug, you should consider the following:
– The body weight of the horse. Horses in ideal body condition may cope without a rug, however, adequate feed and forage are required to prevent weight loss. Underweight animals will benefit from a rug, as it reduces utilisation of internal fat stores for maintenance of body temperature and facilitates weight gain if adequate feed and forage are provided.
– If your horse is wintered out on pasture, which is very exposed to difficult conditions with continual wind and rain, it can cause a large wind chill factor. Such conditions are not favourable to horses, which will find it challenging to maintain body temperature. Extra feed and forage is essential in this situation and a rug could be beneficial.
– How often you intend to ride your horse – if your horse is not clipped, kept out at grass and being ridden once or twice a week, it may not require a rug.
– If your horse is clipped, the type of clip your horse has will have a huge influence on your decision on what rug is best for your horse to keep it warm. Hunter and full clips can reduce the horse’s ability to maintain body temperature by a least 5oC.
– Time available for grooming – keeping a horse clean can make it more practical for the owner if the horse is ridden regularly, especially for field kept horses. For stabled horses, rugging an unclipped horse will keep the coat shorter and smoother, which is a requirement in the showing world.
– The horse’s lifestyle should also be considered, whether stabled or living out full time, it may need extra protection.
– Old and young animals sometimes have problems maintaining their body temperature in colder, wetter conditions.
– The horse’s breed and type will also influence your choice of rug thickness.
– Horses prone to rain scald will benefit from the protection of a rug
– Sick horses are very vulnerable and may be incapable of sustaining their own core temperature, especially if they are not eating normally. Often horses with muscular complications that reduce mobility require extra warmth and benefit greatly from an extra rug.
It is important to consider the above factors when deciding if rugging is essential for your own particular horse’s requirements. The take away message is that horses are very effective at regulating their own temperature if management and feeding allow. However, cooling down is more difficult for horses and therefore over-rugging can be detrimental to the horse’s health. Over-rugging may also cause the horse to heat up only under the rug leaving other areas open to the elements, losing his ability to cool down naturally. This can be stressful for the horse, therefore, it can be more appropriate to manage some horses without a rug.