AS we are now approaching late winter and early spring is on the horizon, it is important to consider what rugs are most appropriate for our horses. Changes of season bring variable temperatures and weather conditions, making it especially difficult to select the most appropriate rug. This challenge is further complicated by every horse having individual requirements depending on age, breed, weight, climate, workload, and even their coats. Horses that are used to the colder weather and have spent most of their time outside, tend to cope better with cooler temperatures than horses that are stabled all the time.
Horses are mammals that maintain their internal body temperature at around 38°C through a well-developed thermoregulation system that controls how much heat is retained or lost. In warmer conditions, the body will lose more heat whereas in colder conditions more heat is retained. The thermoneutral zone (TNZ) is defined as the ambient temperature range where the body can maintain its internal temperature without having to use its temperature regulatory processes. In the horse, the TNZ ranges from 0°C to 25°C. Outside of these temperatures the horse’s body must utilise processes to maintain the 38oC internal temperature.
When the environmental temperature is outside of their TNZ, the horse will use other means to keep warm or cool. Horses may increase their respiratory rate and begin to sweat or look for water to cool off, or to warm up they can increase their metabolic rate using fuel (body weight), look for shelter and allow their limb temperature to reduce to retain warmth in the body. As horses are very adaptable to temperature, an individual animal’s TNZ can vary once they become acclimatised.
How does rugging affect temperature regulation?
Recent studies on the effects of rugs have shown that unnecessary rugging could compromise equine health and welfare, and although studies have not been specifically looking at temperature and rug weight, the findings indicate that different rug types can have a significant effect on the horse’s temperature.
So how do we stop ourselves from over or unnecessary rugging? We need to ask the right questions to gain a better understanding of what factors should be considered when rugging. Consider why your horse needs a rug – is it to keep them warm, is it to keep them dry or is it to keep them clean?
When answering these questions, consider the following:
Environment – Is your horse stabled or living out and do they have access to shelter and good quality forage? Horses that have shelter, forage and can exercise will be able to regulate their temperature much easier than stabled horses on limited forage that have no means to produce heat.
The colder the air temperature, strong winds and rain will affect the rate at which a horse will maintain or lose heat. Consider the materials used to build the stables/ shelter, as heat can be lost by radiation to colder surfaces.
Coat and Condition – The type of coat your horse has will affect how well the horse can keep warm. A clipped horse is less able to keep warm compared to a horse with a thick winter coat, as the horse’s coat traps air between the hairs, which keeps the horse warm. However, when the horse gets wet, the hairs collapse, which can then lead to heat loss. Clipped horses will find it more difficult to maintain heat and will need to be provided with some additional insulation to replace the removed hair. Most horses are clipped to reduce the risk of over-heating during training or competition, however, you should consider how much hair really needs to be removed for the type of work the horse is doing.
The condition of the horse will have an effect on rugging. Traditionally, horses would gain weight during the summer and lose weight during the winter, however, many horses are now prevented from losing weight during winter, having a negative impact on their health. Winter provides an opportunity to promote weight loss in overweight animals, as they use internal fat stores as fuel to maintain body temperature. Rugging overweight horses is preventing this thermoregulation activity and loses the opportunity for weight loss. If rugging is needed for protection again persistent rain or for cleanliness, then a light weight rug would be most appropriate. Alternatively, a horse that struggles to maintain condition may require extra help staying warm and maintaining a healthy weight.
Breed type – The size and breed of the horse can affect the rugging decision, as some breeds retain heat in cold weather better than others and vice versa, for example cobs would have an advantage over “finer” breeds, such as Arabs in colder conditions, but the opposite could be said in hot climates.
Age and Diet – Older and younger horses are more likely to have difficulty coping with the climate changes. Younger horses tend have less body fat and will lose heat more rapidly. Older horses may have health and mobility problems and have a reduced ability to control their body temperature.
The horse’s diet and digestive efficiency will contribute to how well they cope in various weather conditions. Heat production is greater on high fibre diets compared with high starch and/ or high oil based diets. Healthy horses should be able maintain body condition if they have unlimited access to good quality forage.
Knowing which rug and what weight of rug to use can be confusing and, at this time of the year when the weather makes it more difficult, these factors should help you make your decision. While the use of rugs and blankets may be necessary, selecting the right type and weight of rug for your horse is vital. Assessing each horse’s individual needs should be considered to ensure the horse’s health and welfare are not compromised and your horses are not outside their thermal comfort zone.