I’M (just about!) old enough to remember horse care before the advent of modern waterproof, washable and durable equine clothing. When I was about 10 Santa Claus kindly delivered a New Zealand rug for my pony.

Weatherproof materials at the time consisted of wool and waxed canvas so the rug was stiff and unwieldy, with heavy leather straps to hold it in place. When it was wet it weighed more than I did, so getting in on to the pony involved climbing onto a bale beside him and slowly heaving it over his back.

It also required regular scrubbing to clean it, as even if it could have been fitted in a washing machine, it would not have survived the experience. Once clean and air-dried (which took several days) it had to be reproofed with a tin of wax which had been left to soften in a jug of boiling water. Thankfully the waterproof fabric revolution of the late 1980s followed shortly afterwards, and all subsequent rugs and the associated efforts to keep horses warm have been much easier to live with!

THERMOREGULATE

Horses, just like humans and other mammals, are able to thermoregulate in order to maintain a constant body temperature. If too hot the horse will seek shade and if cold they will move out of the prevailing wind or turn their backside to it to reduce the surface area that is exposed to the effects of wind chill.

Horses naturally grow a heavy coat in winter and if left unclipped, unwashed and only lightly groomed their coat will retain its natural oils. These oils help rain water to run off, keeping the skin quite dry even in heavy downpours. The availability of a warm, dry place to lie down avoids the horse getting chilled or wet while resting.

A diet with plenty of good quality grass, hay or haylage is also important as the complex carbohydrates in the forage will be broken down by the gut microbes to release nutrients and energy for the horse. This process of microbial fermentation also releases a lot of heat and is one of the reasons why horses can tolerate the cold so well, especially if they are dry. Anyone who has worked in Kentucky for example will have seen horses turned out and thriving in deep winter snow.

THERMONEUTRAL ZONE

Because humans start to feel cold below relatively high temperatures, many owners assume that horses experience their environment in the same way. However, a horse’s thermoneutral zone (5-20°C) is much lower than that of a human (25-30°C) and horses are unable to tell us if they feel uncomfortably hot or cold.

The thermoneutral zone is the temperature range within which the animal is comfortable and does not need to expend energy in either staying warm or cooling down. As their body temperature drops the horse will respond by increasing its metabolic rate to release heat from the diet and body fat stores. Peripheral blood flow is reduced to minimise heat loss from the limbs and head.

A cold horse is relatively easy to spot – they may look miserable and frequently shiver in an effort to release additional heat. However, the signs of overheating are often more subtle and may consequently be missed, especially if owners don’t realise how cold it needs to be before a healthy and well fed adult horse will be affected by it. If a horse starts to get too hot it will sweat. The evaporation of this solution of water and salts causes increased blood flow to the skin and the release of heat from the underlying tissues. However, if the horse is wearing a rug this ability to cool itself effectively can be compromised, leading to discomfort and a potential risk of heat stress.

Monitor rugged horses closely if they are out in fine weather, especially in unseasonably warm spells. If the horse is sweating under the rug then it is definitely too warm. Steam rising from the withers a tell-tale sign. Put your hand under the rug at the shoulder to check for dampness, if it’s hot and steamy in there take the rug off, rub the horse dry and either wait for the weather to cool down again or apply a lighter rug.

If the horse is left wearing a damp rug it will get chilled once the temperature drops, as wet rugs and hair are not effective insulators. Feeling the horse’s ears is not an accurate method to assess their body temperature. If in doubt, take the horse’s rectal temperature. A value somewhere in the range of 37-38.5°C is typical for a healthy adult at rest.

RUGGING AFTER

EXERCISE

Up to 80% of the energy used by a horse during fast exercise is released in the form of heat, rather than contributing to muscle contractions. This means that the core body temperature can spike rapidly during fast work so the horse will sweat to avoid overheating.

A horse with a full winter coat will get hotter faster, making them less exercise tolerant. For this reason horses performing fast work are typically clipped in winter to help them perform optimally and in comfort.

Avoid rugging a horse as soon as they finish their work as this can cause their muscles to retain excess heat for longer and delay their recovery. Wash or rub them down, apply a light sheet and walk them to keep them from getting chilled before reapplying their rugs after half an hour or so.

Excessive and/or inappropriate rugging has recently been recognised as a horse welfare problem. Modern rugs are much more widely available, affordable, better designed, washable and durable. This has contributed to their more widespread use. Owners apply rugs out of good intentions and a wish to care for their horse. However, direct extrapolations from what is comfortable for a human may not apply to horses. Equine obesity is a rapidly growing problem with severely detrimental effects on horse health and welfare, especially amongst the leisure horse population.

The overuse of rugs is one factor that can contribute to this, as it means that the horse does not have to expend as much energy to keep itself warm. In addition, obesity reduces fertility so it is also a potential problem for breeders.

ADVICE

    • Only rug healthy horses if they specifically need it (below 5°C for unclipped animals and below 15°C if clipped is a practical rule of thumb)
    • Keep thermometers in the stabling area to help you monitor the environment
    • Monitor rugged horses closely for signs of overheating, especially during warm spells
    • Adjust horses’ rugs according to the prevailing weather conditions
    • Have more than one weight rug and change them in response to the weather conditions
    • Ensure all rugs fit correctly and are in good condition
    • Correctly fitted rugs should not result in rub marks or hair loss but a fleece shoulder cover or under blanket may be needed for some very fine coated individuals
    • Wash and dry rugs regularly and ensure any minor repairs are carried out promptly
    • Avoid rugging horses unnecessarily e.g. just to keep them clean (if you must, use a light sheet)
    • Make sure the horse’s coat is clean and dry before applying a rug
    .
    • Outdoor rugs must be waterproof – if they get torn or damaged replace them immediately with an intact rug while the original one is repaired
    • Remove all rugs at least once a week to allow the horse’s skin health and body condition score to be accurately assessed
    • Brush the horse over while the rug is off to remove excess dead hairs, dust etc.
    • Allow horses to cool and dry off after exercise before reapplying their rugs
    • Have a thermometer to check body temperature if in doubt
    • If the horse is getting static electricity in their coat from nylon rugs try lightly wiping them over with some baby clothes fabric softener dissolved in warm water
    • Provide plenty of good quality forage, especially in cold weather
      • spells
    • Avoid over-grooming or washing unclipped horses who live out
    • Provide access to a dry, sheltered area so the horse can get out of the sun or wind and rest without getting too hot, cold or wet
    • Rug the thin, old, young or clipped horses before the healthy, hairy and hardy individuals!

    • Finally, the advent of wearable technology and smart clothing for humans may soon make the transition to horses. Several horsewear companies already offer apps and other services to help owners evaluate their horses’ rugging needs. Rugs with in-built temperature sensors that will link to your smartphone and alert you if the horse is getting too hot or cold are coming on the market, along with wearable devices that, as well as monitoring heat levels, can also alert owners to excessive lying or other abnormal activity levels for example. Let’s just hope that they are all also washing-machine proof, so that the days of laboriously scrubbing and reproofing canvas rugs remain firmly behind us!

    RUG TERMINOLOGY

    Denier: this value refers to the number and durability of the nylon fibres in the material. The higher it is, the more waterproof and durable the fabric will be. Equine outdoor rugs typically have denier values of 1200+.

    Weight: the amount of polyester filling in the rug. It’s measured in grams and indicates how much insulation the rug will offer. Lightweight sheets start at 0g and a heavy turnout rug is typically in the region of 400g.

    Karen Dunne, MA, CertEM (StudMed), MVB. Veterinary nursing programme director at Dundalk Institute of Technology (DkIT). Member of the education, research and industry (ERI) and equine groups of Veterinary Ireland. My interests include large animal nursing, equine and stud medicine and education.