How should you be rugging your horse this winter?
- Horses can regulate their temperature between 5 and 25 degrees Celsius.
- Many owners over rug their horses and are unaware that despite the fact it is done with the best intentions it is actually cruel.
- Heavy weight rugs should only be used in exceptional circumstances such as very sick foals or very thin geriatric horses.
- Over rugging affects the horse’s ability to regulate its own body temperature.
- Studies show that most unclipped horses will get too hot and suffer distress when rugged.
- Horses are forage eaters and their digestion acts as a fermentation vat which can be “turned up” in cold weather to keep them warm.
- They can also conserve heat by closing down peripheral circulation.
- Unclipped horses have thick coats that stand up when it’s cold and trap air as a layer of insulation.
- Clipped horses will need a rug, however, take the environment into account, consider the type of shelter and the weather, horses can cope with cold and dry weather better than cold and wet conditions.
- Most clipped horses will only require a light to medium weight rug depending on breed and type.
- A horses winter coat only has a tog rating of about 1-2, a humans summer duvet has a tog rating of 4.5, so by replacing a clip with a rug similar to a summer duvet is already more than doubling the natural insulation.
There has been a lot of attention recently in both the equine press and online forums about the welfare implications of rugging horses. The general consensus is that the over rug their horses and many studies have proven this. Yet, still when driving around one sees small, hairy ponies and large cobs turned out in medium weight rugs with necks, perhaps solely because it is the done thing.
It has been well documented for several decades that horse can regulate their temperature between 5 and 25 degrees Celsius (this is known as the thermo-neutral zone or TNZ). Thousands of years of evolution have resulted in horses being able to cope with these extremes. They are forage eaters and have a large caecum which acts as a fermentation vat and releases heat to the body’s core. In cold weather the fermentation rate is simply “turned up.” The horse also has the ability to withdraw heat from its extremities in order to conserve heat in its core, by closing down the peripheral circulation. Conversely, they have the ability to lose heat by dilating its numerous superficial veins and allowing heat exchange to the outside environment (think steaming racehorse at the end of a race). The horse also has a thick winter coat which can stand up when cold and trap air as a layer of insulation. Additionally, it has a low surface area to mass ratio and will lose heat at a relatively slower rate than a smaller animal. Large animals are therefore better adapted to colder climates. Horses are unusual as they are found in a variety of climates and can adapt to the majority of conditions. Possibly the best example of this is the Arab horse in the desert where temperatures can be at or even outside both limits of the horse’s thermo-neutral zone within a period of 24 hours. Certain breeds have adapted metabolisms to suit the natural climate from where they originate. The Przewalski horse of the Russian Steppes has adapted to eat poor grasses and withstand extremes of cold, and Brumbies in Australia although not indigenous have adapted to survive on poor grass in hot climates. The native ponies in the UK have evolved to gain weight as fat on the lush spring grass, which produces the best quality milk for the foals and provides a store of energy which is later utilised in the more severe conditions in winter. It is therefore both natural and normal for them to come out of the winter looking slightly poorer than then entered.
So what is the effect of rugging?
The simple answer is that it affects the horse’s ability to regulate its own body temperature. If the horse is too warm it cannot lose the heat to the surrounding air due to the insulation of the rug. Research from Hartpury College by AE Brown published in May 2018 monitored the skin temperature of 15 horses with the Orscana device. All the horses were wearing rugs chosen by their owners and the average air temperature was 5.8 degrees. The mean temperature for all the horses was above the horses TNZ but the horses with lighter rugs showed less of an increase. A further study by Kim Hodges, an MSc Student at Duchy College published in September this year demonstrated that a fleece rug increased skin temperature by 11.2 degrees and a lightweight quilt by 15.8. The skin surface temperature for these horses was 24-30 degrees compared with that of non-rugged controls at 12.5 degrees when the air temperature was 4-5 degrees C.
These two studies clearly demonstrate that most unclipped horses will get too hot and suffer distress, if not full blown heat stress when wearing rugs. Native ponies and those prone to weight gain will not get the opportunity to mobilise their fat stores over the winter to keep them warm and so will continue to gain weight. Winter rugging together with unnecessary additional feeding are important causes of insulin resistance, Equine Metabolic Syndrome (EMS) and the inevitable laminitis that results.
What about clipped horses?
Obviously, if your horse is clipped you will need to replace that insulation. It may surprise most readers that the horse’s winter coat has only a TOG value of about 1-2. A human summer duvet has a TOG rating of about 4.5, so replacing its clip with a rug of similar weight is already more than doubling its natural insulation. Some of the thicker heavy weight rugs could have TOG values of 15 which the horse’s physiology cannot withstand. Pay careful consideration to the surrounding environment when choosing rugs – remembering that if the horse is turned out and moving about it will generate heat which may not be lost from the rug. Other important factors are the degree and type of shelter (hedges, walls, terrain) and the weather conditions; Horses are better adapted to cope with cold and dry than wet conditions. Sleet may well be more of a challenge to your horse, utilising more calories to keep warm than a hard frost.
There should really be no need for heavy weight rugs apart from in exceptional circumstances such as very sick foals or very thin geriatric horses which do not have the same ability to regulate their core temperature. Most clipped horses will only require light to medium rugs depending on their breed and type. The Grooms’ List has published a very useful chart to use as a rugging guide.
Studies have shown that most owners are influenced by peer pressure rather than science when rugging their horses. This has the potential to result in whole yards of hot, stressed, overweight horses which could also be susceptible to laminitis! Remember that if you feel cold, it definitely does not mean that your horse does too and if he feels at all clammy behind his shoulders he is too hot. It is far better to feed extra hay when the weather is bad which will fuel his natural heater than to wrap him up to the extent that he cannot maintain his equilibrium.