Horses have the ability to naturally adapt to the temperature of the environment 1. When horses are exposed to colder temperatures for a longer period of time, during the winter, the body adapts through thermoregulation 2.
The horse's body temperature is regulated through the production of heat in the body and the release of heat to the environment. When the ambient temperature drops, receptors located on the skin, among other things, send signals to the hypothalamus 3. These signals ensure that the body acclimatizes to the lower ambient temperature. The skin ensures that as little body heat as possible is lost by reducing the flow of blood to the surface of the skin 3. In addition, the fur hairs stand on end and hold air to improve insulation and retain heat 4. Body heat is produced through metabolic processes in the body, including the digestion of nutrients in the digestive system. The metabolic processes require energy from food to provide the body with heat 5,6. Therefore, when the temperature drops, the horse's nutrient and feed needs increase to maintain body temperature 6.
| "Body heat is produced through metabolic processes in the body."
Roughage contains a high amount of fiber which is digested by microorganisms in the digestive system into volatile fatty acids 7. Fermentation of the fiber produces heat which provides the horse with warmth from the inside to regulate body temperature 8. In contrast to the digestion of fibres, the digestion of starch from concentrates provides little heat because starch is digested by means of enzymes and this process produces little heat 9. It is therefore important to provide the horse with sufficient roughage during the winter. Because roughage forms the basis of the diet, it is recommended to provide 2 to 2.5% of the horse's body weight in roughage. For a 500 kg horse, this would be between 10 and 12.5 kg of roughage per day. If the temperature falls below freezing point, it is advised to feed 10 to 15% extra roughage to support the regulation of body temperature 10.
Studies have shown that feed intake of wild horses changes seasonally 11. In winter, less feed is available due to less grass and plants growing, which reduces feed intake 12. In order to still be able to regulate body temperature in colder temperatures, stored body fat is broken down and used as fuel 11. These reserves are built up during the fall when food is readily available. Research indicates that during the fall, the horse's feed intake increases, relative to other seasons, to store body fat in body tissue that can be used during the winter 11. In addition, it has also been shown that this increases the body weight of the wild horses per season. fluctuates and decreases sharply, especially in winter 11,13. It is therefore advised to ensure that the body condition score (BCS) of the horse is slightly higher than normal at the start of the winter, in order to provide the horse with extra reserves during the winter 10. In addition, it is advised to increase the BCS monitoring during the winter to measure whether the energy requirement of the horse corresponds to the diet to prevent under or overweight.
Referenties 1. Hammer, C., & Gunkelman, M. (2020). Effect of Different Blanket Weights on Surface Temperature of Horses in Cold Climates. Journal of Equine Veterinary Science, 85: 1-3. 2. Cymbaluk, N. F. (1994). Thermoregulation of horses in cold, winter weather: A review. Livestock Production Science, 40(1): 65-71. 3. Mejdell, C. M., Bøe, K. E., & Jørgensen, G. H. M. (2020). Caring for the horse in a cold climate—Reviewing principles for thermoregulation and horse preferences. Applied Animal Behaviour Science, 231: 1-8. 4. Morgan, K. (1997). Thermal insulance of peripheral tissue and coat in sport horses. Journal of Thermal Biology, 22(3): 169–175. 5. Cymbaluk, N. F. (1990). Cold housing effects on growth and nutrient demand of young horses. Journal of Animal Science, 68(10): 3152-3162. 6. McBride, G. E., Christopherson, R. J., & Sauer, W. (1985). Metabolic rate and plasma thyroid hormone concentrations of mature horses in response to changes in ambient temperature. Canadian Journal of Animal Science, 65(2): 375-382. 7. Dougal, K., de la Fuente, G., Harris, P. A., Girdwood, S. E., Pinloche, E., & Newbold, C. J. (2013). Identification of a Core Bacterial Community within the Large Intestine of the Horse. PLoS ONE, 8(10): 1-12. 8. Santos, A. S., Rodrigues, M. A. M., Bessa, R. J. B., Ferreira, L. M., & Martin-Rosset, W. (2011). Understanding the equine cecum-colon ecosystem: Current knowledge and future perspectives. Animal, 5(1): 9. Merritt, A. M., & Julliand, V. (2013). Gastrointestinal physiology. In: Geor, R.J., Harris, P.A., & Coenen, M., (eds.). Equine Applied and Clinical Nutrition, Saunders Elsevier: China. 10. Harper, F. (2004). Winter Horse Feeding. Extension Horse Specialist Department of Animal Sciences, 23(1). 11. Arnold, W., Ruf, T., & Kuntz, R. (2006). Seasonal adjustment of energy budget in a large wild mammal, the Przewalski horse (Equus ferus przewalskii). II. Energy expenditure. Journal of Experimental Biology, 209(22): 4557-4565. 12. Arnold, W., Ruf, T., Reimoser, S., Tataruch, F., Onderscheka, K., & Schober, F. (2004). Nocturnal hypometabolism as an overwintering strategy of red deer (Cervus elaphus). American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 286(1): 174-181. 13. Scheibe, K. M., & Streich, W. J. (2003). Annual Rhythm of Body Weight in Przewalski Horses (Equus ferus przewalskii). Biological Rhythm Research, 34(4): 383-395.
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