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Winter Rugging

There has been a lot of attention recently in both the equine press and online forums about the welfare implications of rugging horses.

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 general consensus of all the available science is that the majority of owners 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. It appears that horse people will listen to the science and then do as they have always done.

I have personal experience of a Shetland X Welsh, 11 hand pet pony which does no work, and which has Equine Metabolic Syndrome and has had laminitis wearing a rug because it looks “sweet” and it is a “little chilly outside”.  The pony is stabled at night in a wooden stable which is known to be better insulated than a brick or stone one. When questioned about the shelter on the Welsh mountains or Shetland Isles the owner just giggled and said that they felt “sorry” for the pony and that the “Big horses” (Hunter clipped) were wearing rugs! This owner is in complete denial of the cruelty that she is inflicting albeit for the best intentions.

It has been well documented for several decades ( to my personal knowledge at least since I left Veterinary School in 1984!) 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 it has the ability to lose heat by dilating its numerous superficial veins and allowing heat exchange to the outside environment. (Think about a 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. The horse is unusual as it is 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 a little poor.

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 this year 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.

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.

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.

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. I learned this to my cost when my fit lean racehorse, with virtually no excess body fat chose to gallop around the paddock in his medium weight rug and subsequently required fluid therapy due to the degree of severe sweating and dehydration which ensued.  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 in February may well be more of a challenge to your horse, utilising more calories to keep warm than a hard frost on Christmas morning.

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 guide which can be found here

Studies have shown that most owners are influenced by peer pressure rather than science (or common sense!) 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 you 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.

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