Over-rugging is a hot debate, quite literally. All too often are horses over-rugged as their owner is feeling a bit nippy. Horses have a wonderful capacity of self-care, of which their internal thermostat is included. Over-rugging actually causes many more problems than those associated with a cold horse and many ‘manmade’ issues can be avoided with correct usage of rugs.

So, how should you rug your horse? To analyse deeper, we need to step back and analyse the horse itself and their wonderful biomechanics.

The science

Before human interaction came into play, horses lived freely in the wild, self-regulating their temperature (a process called Thermoregulation) to ensure it remained consistent, sitting between 37.2 and 38.3°C (99-101°F). Horses generally use energy to keep warm, however, studies show that an air temperature must continually sit below 9°C before a horse uses any of its energy maintaining its own body temperature.

We all know horses are grazing animals and will easily graze for up to 19 hours a day. During this time, the digestion of long fibres and forage in the hindgut continually produces heat through the peristaltic movement. This movement and the increase in blood flow ensures a continued heat source for the horse, which is why ad-lib forage is so often recommended, particularly through the colder Winter months.

Over thousands of years, as the horse has roamed and evolved, they’ve learnt to adapt to, and deal with, the ever-changing climates. One thing has remained consistent throughout and that is their foraging and grazing manner and their ability to self-regulate, the two of which go hand in hand. As horses have become domesticated, their body regulation hasn’t changed to the extent in which our management of them has. Despite us often offering them a restricted diet, they still manage to control their temperature, as they adapt to our feeding regimes.

Over-rugging issues actually go beyond the simplicity of the horse getting warmer. Excessive overheating can cause horses to show signs of colic as well as increasing their chances of developing laminitis – a life threatening issue in itself.

What happens when my horse becomes too hot?

Horses have a number of ways in which they try to cool themselves down, including;

• seeking shelter from direct sunlight,
• sweating, which dilates the blood vessels and increases the respiratory rate,
• the horse lowers its metabolism and will eat less so less internal heat is produced.

A general rule is a skinny horse is more likely to struggle to keep warm whereas a fat horse is more likely to struggle to keep cool

If none of these attempts are successful then the horses welfare can be significantly affected as the core body temperature continues to rise. Once this level has been achieved, hormone levels are affected. The result of which can lead to;

• the horse eating less to try to limit the production of heat in the body resulting in undesired weight loss,
• the body may not be able to fight disease as the horses immune system drops,
• lactating mares may suffer with milk production,
• breeding stallions may not be able to produce sperm so efficiently,
• an increase in chances of the horse becoming obese,
• a significantly increased risk of Laminitis.

The link with Laminitis

Many believe Laminitis is just a seasonal grass related issue, however over-rugging can increase your horses chance of developing the disease in Spring. In the wild, horses would gain weight through the Spring and Summer and use that weight to keep themselves warm over the Winter, as they gradually lose the weight. The result is that come Spring, their weight is on the lower side so they can start eating the sugar-rich grass with little problems. When over-rugging through the Winter months, the horse doesn’t use up any of its weight, which throws his hormone levels off balance, which can have a detrimental impact on his health. Laminitis in unfortunately a terminal disease and can be fatal.

Seasonal rugging

Having covered the detrimental effects of over-rugging, how can you be sure what and when to rug? Spring and Autumn are particularly trying times as the temperature fluctuates so much – the difference between first thing in the morning and the middle of the day can easily be 10°C, making rugging in the morning rather trying. You almost certainly need to change rugs every morning and afternoon for these seasons to ensure your horse remains as happy as can be, and the perfect comfortable temperature. Is it better for your horse to be too cold or too hot?

As previously discussed, horses can self-regulate, so if they’re too cold, they can warm themselves up quite easily, however the same can not be said if they’re too hot. Cooling themselves down when they’re over-rugged is practically unachievable. Therefore it is always best to leave your horse naked or to put the lighter weight rug on your horse in Spring and Autumn when the temperature difference is so excessive.

Rugging at nighttime in the Spring and Autumn is entirely dependant on a number of factors including; whether your horse is clipped; is your horse living in or out; is your horse young, old or unwell; has your horse recently been bathed and therefore has had all oils removed the skin?

Very few rugs are required in the Summer months – your rug of choice would most likely be a fly sheet, which due to its colour acts as a heat defensive system, retracting the suns rays, keeping your horse cooler for longer. Alternatively, even in the evening, you may wish for a summer sheet, just to keep the horses coat clean.

The table below shows an example of good rugging practice for different situations.

	Clipped – stabled	Clipped – lives out	Unclipped – stabled	Unclipped – lives out
10°C or higher	Lightweight or fly rug in Summer months	Lightweight or fly rug in Summer months	No rug/fly rug in Summer months	No rug/lightweight if wet and windy or fly rug in Summer months
5 – 10°C	Medium weight	Medium weight with neck	Lightweight	Lightweight with neck
0 – 4°C	Heavyweight	Heavyweight with neck	Medium weight	Medium weight
-10 – 0°C	Heavyweight with neck	Heavyweight with neck and sheet underneath	Medium weight	Medium weight with neck
-10°C or colder	Heavyweight with neck and thin stable rug underneath	Heavyweight with neck and stable rug underneath	Heavyweight	Heavyweight with neck

Generally it is better for horses to be slightly too cold than too hot. Horses that are clipped, under the weather or elderly for example, will require more rugging through the colder Winter months than ‘good doers’, Native Breeds and those that are unclipped. Every horse is different and should be treated as an individual case. The table above is to be used as a guide only, if you’re still unsure please do speak to your Vet. Do try and use your initiative, speak to a professional and you’ll have a happy, healthy horse.