It is officially still autumn, but it has felt rather wintery out there, and I even got caught in a heavy hale shower the other day (thankfully when my horse and I had got back from a hack, rather than during!). This seasonal change has forced us all to consider the winter ahead, and how we can manage our horses best during this time.
Horses use energy keeping warm, and the lower critical temperature for adult horses (the temperature below which inner heat production is increased to maintain body temperature) acclimatised to outdoor winter weather is about -15°C. Researchers have estimated that cold weather increases horse’s dietary energy requirements by about 2.5% for each degree centigrade below -10°C.
Adults horses manage relatively well until temperatures drop under -10 to -15°C, which doesn’t occur often in the UK. However, wind chill and rain make a difference and horses will use more energy to keep warm in such conditions at much less cold temperatures than the ‘critical’ -10°C. Young horses and more especially foals have a higher lower critical temperature and will have increased energy requirements at less cold temperatures.
To ensure your horses stays warm, feed plenty of forage – ideally ad lib – and they will maintain a healthy weight on this regime. Forage is retained in the horse’s hindgut where it is fermented by micro-organisms, releasing useful nutrients and heat. The heat created from this forage digestion is a useful source of warmth for horses, especially those who live outside. 66% of the energy in meadow grass hay is converted to heat during digestion, whereas just 20-30% of the energy in cereal grains is converted to heat during digestion. Another two slices of hay is more warming than a bowl of concentrate feed even if it is mixed with warm water!
Shelter and rugs can help reduce the extra energy required to keep warm. Researchers have shown that rugging horses in cold weather reduced heat loss in cold weather by 18%, and offering shelter reduced heat loss by 9%. Both rugging and shelter reduced heat loss by 26%. Rugging thin horses or those who struggle to maintain weight is recommended, especially in windy, wet weather. On the other hand, horses that need to lose weight should not be rugged unnecessarily because you don’t want to save them energy expenditure. Nevertheless, for welfare reasons they should ideally have access to shelter in inclement weather.