WEATHER
and HORSES
Story and Photos By Alessandra Deerinck
The natural conditions
of the weather, related to the seasons are something that is beyond human control. Temperature and humidity changes happen throughout the year, but can also deeply change in a day, and affect the metabolism of any living animal. Animals that have a choice in how to cope with the weather changes, have developed different ways to do so, but when they live in a domestic environment, they are deeply influenced by how we keep them.
The equine species has a very efficient ability of adapting to where it lives. Horses are warm-blooded animals, and their core body temperature stays within a certain interval even when there are big variations in the environmental temperature. . A sudden exposure to cold causes catecholamines to rapidly increase metabolism, while thyroid hormones cause the long-term cold adaptation. The body heat comes from the metabolism in all the body tissues. Animals with a higher basal metabolism, like growing or working animals, and pregnant or lactating mares, have a higher basal heat production. At rest, the heat production takes place mainly in the heart, liver, kidneys and brain, but during exercise the muscles produce a very high quantity of heat. Surplus body heat is dissipated to the cooler surroundings, mainly over the skin surface. The body size also matters, a large horse has more mass to produce heat, but a relatively smaller surface to dissipate it, compared to a similarly built but smaller horse. The equine limbs have a “radiator system”, where the arteries and the veins run close together in such a way that the warm arterial blood coming from the body core warms up the cooler blood in the veins. This situation reduces the temperature of the distal limbs, and also reduces the total heat loss.
EQUINE Health
Horses cope with temperature changes by seasonally changing their hair coat. The day-length regulates shedding and hair regrowth, and the coat quality is influenced by the local climate conditions and management factors. In most of the USA the heavy winter coat will start to grow sometime in late August. The hair coat, skin thickness, and subcutaneous adipose tissues have an important function on insulation properties and heat loss, and are related to natural or artificial selection. In fact, there are genetic differences among individual horses and breeds in their ability to grow a thick winter coat. A horse’s coat has guard hairs which are longer and stiffer, and an undercoat that is soft and fluffy. The guard hairs protect the undercoat from dirt and water. The undercoat traps warm air and acts like a layer of insulation for the horse. There are natural oils that coat the hair and make them water resistant. The mechanism that creates the insulation works through piloerector muscles connected to each hair, that make the hair stay up or lay flat. When they stand up a layer of warm air remains trapped between them above the surface of the skin. When hair lies 48
down the warm air is released, cooling the area above the surface of the skin. Horses can tolerate temperatures down to 5°F before their body temperature drops, but certain conditions like rain and wind can challenge a horse’s ability to keep warm. Rain flattens the hair coat, preventing the undercoat from providing the insulating layer of warm air. Wind blows the warm air away from the surface of the skin. Interestingly, snow is less of a problem, because it collects on the horse’s coat without wetting it and acts as a layer of insulation.
BLANKET OR NO BLANKET?
Blankets can be a quick remedy in case of wind or rain. When a horse has a natural winter coat, is healthy and in good body weight, the weather is not too windy or raining, with a temperature above 5°F, blanketing is not needed. If a horse is clipped, therefore deprived of his natural physiologic defense against cold temperature, we must use a rug and be very attentive about the material of the rug and when to apply it or remove it. Another instance when blanketing a horse can be helpful is when he is sick or injured, older, with weight issues, has difficulty moving around, or has been recently moved to a colder climate. Horses can adapt to moving to a different climate, but need at least two to three weeks to do so. In order to use a blanket, to keep a horse warm and safe, correct fitting is very important. When blankets are too small can cause sores and do not produce enough warmth. When a blanket is too big it can allow too much cold air underneath, or be too loose and the horse can get tangled up, or even manage to slide out of it.
www.EliteEquestrianMagazine.com
