Many horses tend to lose weight during winter. This is mainly because as temperatures drop and the number of calories a horse needs to burn to stay warm and maintain their body temperature increases, therefore a horse needs to eat more calories to maintain their weight. In many parts of the country the quality of pasture available also falls, which means a horse gets less calories from its pasture during winter which may also contribute to weight loss.
A horse needs at least 1% of their body weight per day in roughage to maintain a healthy digestive system. However, in winter months horses should be given at least 1.5 to 3% of their body weight in some form of forage, especially if your horse lives outdoors.
Horses are designed to heat themselves through the digestion of forage (hay or pasture) in the hindgut. Hay is a “slow burn” food for horses, meaning it is digested more slowly, generating metabolic heat longer than would be provided by concentrates. Digestion and fermentation of hay produces heat that helps the horse maintain its body temperature during winter. Feeding additional good quality grass hay is the simplest way to ensure your horse will meet its energy requirement in the cold. If a horse is eating a round bale or large square, they should be fine in terms of eating enough to maintain energy balance. If you limit feed (feeding out 2 x per day etc.), you should consider increasing your horses hay by 1 to 3 biscuits of extra hay per day. If you are worried about excess weight from increased hay consumption, look for a long-stemmed, high-fibre grass hay that is good quality and this is lower in overall nutrition and calories overall.
The fibre obtained from hay is necessary to keep the digestive system of the horse functioning properly. Without this hay fibre, horses will seek out other sources of fibre including bedding and wood fences or trees to satisfy their needs. Adequate fibre from hay is even more critical during the winter months since it is the feed ingredient that keeps horses warm during cold weather.
Older horses who have trouble holding their weight in winter may lack the dental health to properly chew some hay. For such horses, a chopped hay substitute or pelleted substitute may be an important part of maintaining their body condition over the winter months.
In conclusion, energy intake is the most critical factor in determining how readily a horse develops a tolerance for cold. So yes, horses often need to be fed more hay throughout winter and the colder months. If a horse does not eat enough energy to offset the heat loss due to the cold, the horse loses weight. A plentiful supply of good hay is your horse’s best defence against cold, it could be in the form of long stem hay, chopped hays, forage-based cubes, or combinations thereof.