As we begin to enter into the colder fall and winter months we need to think about how to prepare our horses for colder weather. With colder weather usually brings more wind along with rain and/or snow. Our equine companions have a much higher energy requirement to maintain body temperature during these cold, wet, and windy days. A horse can quickly lose weight if not fed properly to compensate for these increased energy demands.
As we approach colder climates, it is ideal to have your horse in good body condition before colder weather hits. Once it is cold it is much more difficult to increase the body condition on a thinner horse. An adequate amount of fat cover serves as a good insulator and a source for energy reserves. You essentially want to precondition your horse for the approaching colder weather.
For horses in good body condition and a heavy winter coat we consider their critical temperature to be around 30 degrees Fahrenheit. For thinner horses or those with less of a winter coat, the critical temperature will be lower. Energy requirements will increase 2 Mcal/day for every 10 degree difference below the critical temperature.
This means you will need to increase the hay at least 2 lbs/day per 10 degree difference. For normal climate conditions adult horses should consume about 1.5-2% of body weight in hay (a 1000 lb horse needs 15-20lbs/day). Hay will give horses the greatest heat production during the digestive process. Hay is a high fiber source that is utilized through bacterial digestion within the cecum and the large colon.
In contrast, grains are absorbed and digested in the small intestine, which will generate less heat than hay digestion. Although hay is a better heat producer, some horses do require extra supplementation (i.e. grain, fat supplementation, pelleted feeds) to maintain body condition. In preparation for a cold front it is helpful to increase the hay 24 hours prior to the expected temperature change.
Both wind and rain increase the energy requirements beyond that of cold alone. At 32 degrees Fahrenheit with 10-15 mph winds you need to feed a 1000 lb horse 4-8 lbs/day of extra hay. At 32 degrees Fahrenheit with rain or snow you need to feed a 1000 lb 6 lbs/day of extra hay. At 32 degrees Fahrenheit with rain and wind you need to feed a 1000 lb horse 10-14 lbs/day of extra hay to meet the energy requirements.
Many horses will not eat this much extra hay, but giving them the option when you have both wind and wet conditions will help keep them warmer. Extra fat supplementation (rice bran, vegetable oil, corn oil) and/or warm concentrate (grain) mashes are also helpful.
Water consumption usually decreases in the cold weather, which can contribute to a higher incidence of impaction colic. To encourage water consumption keep water tanks from freezing and remove ice from tanks and buckets. You can also encourage water consumption by allowing unlimited access to a salt block. Horses should drink 8-12 gallons of water/day.
A heavy winter coat is the first defense in cold weather as it is a great insulator. Hair will stand up which traps and retains body heat. Once the hair is wet, though, there is a loss of insulating ability. As long as your horse has a good heavy winter coat and a shelter to get under during wet conditions, blanketing is not necessary.
If your horse has a minimal winter coat or does not have access to shelter during wet weather it is okay to blanket as long as the blanket is waterproof. Older horses and horses in poor body condition benefit from a winter blanket that is waterproof. Allowing access to shelter is important during windy and wet conditions. A 3-sided shelter (with the open side opposite of the prevailing wind) or a timberline work well as wind breaks.
Dr. Tanya Balaam-Morgan
Large Animal Veterinary Services
PO Box 247
Chilcoot, CA 96105