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Cold weather increases forage requirements

Cold weather increases forage requirements

The horse is a homeothermic animal which regulates its body temperature. When the horse is within the temperature range where it does not have to get rid of excess heat or produce extra heat is called that the horse is in its thermo-neutral zone. The lower critical temperature is the lower limit of the thermo-neutral zone where the metabolic heat production is increased for the horse to be able to maintain body temperature. The upper critical temperature is the upper limit of the thermo-neutral zone and is the temperature at which evaporative heat loss must be increased to lower body temperature.

The thermo-neutral zone and the lower critical temperature for horses vary with age, body condition, breed, season, climate and importantly energy intake. A high energy intake increases the metabolic heat production and thereby decreases the lower critical temperature. Studies have shown that yearlings with free access to feed had an estimated lower critical temperature of – 11°C and yearlings with limited access to feed had an estimated lower critical temperature of 0°C. When it is cold and the growing horse has to increase its heat production it spends the energy supposed to be used for growth and studies have shown that young horses grow slower in cold temperatures. For an adult 500 kg horse the increased energy requirement for heat production has been estimated to about 1.5 MJ metabolizable energy per day for each degree Celsius below the horse’s lower critical temperature.

Type of feed also affects the horse’s heat production. More heat is produced when degrading forage compared to concentrate, because forage is chewed more and the microbial fermentation in the hindgut implies a greater heat production. Good quality forage is therefore an excellent way for the horse to keep warm during cold winters.

Sara Muhonen, AgrD

References:
Blaxter K. 1989. Energy metabolism in animals and man. Cambridge University Press, Cambridge.

Cymbaluk NF. 1994. Thermoregulation of horses in cold, winter weather: a review. Livestock Production Science 40, 65-71.

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