By: Dr Rosie Alcorn BVSc PG Cert VPS Cert AVP MRCVS
A few weeks ago, we discussed a horse’s needs after clipping. This week, we’re taking a closer look at how horses keep themselves warm, how much extra energy they require in cold weather, and what we can do to ensure they remain comfortable and healthy throughout winter. Understanding these principles is key to effective winter horse care.
The thermoneutral zone (TNZ) is the range of environmental temperatures in which a horse can maintain its normal body temperature without expending extra energy. Within this range, the horse stays warm without needing additional metabolic support.
The lower critical temperature (LCT) is the point at which the temperature drops low enough that the horse must start using extra energy to maintain body heat. Below this threshold, the horse increases metabolic heat production to compensate.
Horses generate heat in two main ways:
1. Digestive heat: Fibre fermentation in the hindgut produces substantial warmth—another reason why forage is essential during winter.
2. Muscle activity: Movement generates heat. Horses may increase their activity levels or begin to shiver when cold.
A horse’s LCT varies widely and can be influenced by several factors:
Age: Older horses and very young horses often struggle more in cold conditions. Foals have a significantly higher LCT.
Weight and body condition: Thin horses have less natural insulation.
Environment and acclimatisation: Horses gradually adapted to colder weather cope better than those suddenly exposed to winter temperatures.
Coat length and quality: A thick winter coat dramatically lowers the LCT. Clipped horses have a much higher LCT.
Weather conditions: A wet coat increases heat loss and raises the effective LCT.
Breed differences: Hardy breeds such as Connemaras tolerate lower temperatures better than finer-coated breeds like Arabs.
Underlying health issues: Dental problems, metabolic disorders, or general ill health can impair a horse’s ability to stay warm.
A fully clipped, fit horse can have an LCT as high as 15.5°C, meaning it begins to expend extra energy at mild temperatures. In contrast, a horse with a full winter coat and good acclimatisation may tolerate temperatures as low as –15.5°C before needing additional energy.
For most horses, the average LCT is around 5°C.
1. Provide Shelter
Horses should always have access to a stable or field shelter, particularly during cold, wet, or windy weather. Wind chill and dampness can significantly increase heat loss, even in hardy types.
2. Feed for Warmth
For every 1°C the temperature falls below a horse’s LCT, it needs an additional 2 MJ of energy simply to stay warm. This is roughly equivalent to:
0.25 kg of extra hay, or
160 g of Sensi-care Extra
per degree below the horse’s LCT.
Increasing forage is usually the most effective way to supply this additional energy. The heat released during fibre digestion not only fuels the horse but also provides long-lasting warmth from within.
3. Rugging in Winter
Rugging should be tailored to the horse’s coat, condition, workload, environment, and individual tolerance to cold. While debates about over-rugging will continue, a fully clipped, fit horse typically requires at least a medium-weight rug to remain within its LCT during colder spells.
Unclipped horses or hardy breeds may cope well with lighter rugs, or even no rug at all.
Understanding how horses regulate their body temperature and the factors affecting their lower critical temperature enables us to make informed management decisions throughout winter. By providing adequate shelter, adjusting feed to meet increased energy demands, and rugging according to each horse’s individual needs, we can support their natural ability to stay warm.
Every horse is different, so regularly assessing their condition, behaviour, and environment is essential. With the right approach, horses can remain healthy and comfortable even in the coldest months.
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