As most parts of the US head into the colder months one of the concerns we as horse owners share is how does cold affect the nutrient requirement of the horse. The nutrients required by the horse include water, energy, protein, minerals, and vitamins. Of these, only the horse’s energy requirement is affected by the environment. The amount of water required is not significantly changed based on environmental factors but how the horse meets their water and other requirements may be altered.
Most horses require about 8-10 gallons of water per day for maintenance. This is does not include water needed as the ambient temperature increases, milk production in lactating mares, or work-related needs. Adequate water intake is important in helping the horse maintain body temperature. An example of “where” the horse receives this water can be shown by the example shown:
As you can see from this example, a horse will drink very little water when they are on pasture that contains a relatively high-water content. That same horse will get almost all their daily water requirement from a bucket, tub, trough, creek, etc., when consuming hay. Overlooking this change in water source is one of the reasons we see more impaction issues in the winter than summer. The other is frozen water sources or water sources difficult to reach. Water temperature may also affect intake. Very cold water, near freezing, might restrict intake. For those living where snow is prevalent, it is not a replacement for water.
A change in water intake also affects feed intake. Remember a decrease in water intake equals a decrease in feed intake. If they are not drinking, they will not be eating.
Feed intake brings us to the nutrient that is impacted the most. Energy requirements are impacted more by environmental conditions than any other nutrient.
If a healthy mature horse can acclimate as the seasons change, the lower critical temperature (LCT) is 10°F (-12°C). Yearlings and two-year-olds have a lower critical temperature near 30°C (-1°C). Debilitated, old, and very young horses have a much higher LCT. This is based on dry conditions and no wind. Wet conditions have a dramatic affect on the LCT. See the examples below. A decrease of 1°F in LCT results in an increase in 1.4% requirement. The example is for a mature horse who has a maintenance requirement of 16.7 Mcal/d.
Often, we see a horse loose excessive weight during winter when being ridden/worked. Below is an example of what environment and work combined can do to daily digestible energy requirements.
Protein, mineral and vitamin requirements are not significantly impacted by environmental conditions. Any additional changes in these are usually compensated by increased feed intake to supply the necessary digestible energy.
As we head into the colder months, a little planning will go along way in helping us keep our horses safe, well fed, and comfortable.