A mature horse will require 25% additional DE when the temperature is 31 degrees F (10 degrees below LCT). A mature horse weighing 1000 lbs will have an average DE requirement of 16.7 Mcal (16700 calories) per day. If this horse is eating 12 lbs of hay @ 800 cal/lb, he/she would consume 9600 kcal of DE from hay, and would require another 7100 kcal DE from grain, which using 1200 kcal/lb as an average for grain, would amount to being fed 5.9 lbs of feed.
At a temperature of 31 degrees F, the energy requirement for this mature horse would increase to 20,875 kcal of DE (16700 maintenance X 1.25). The common assumption is that we need to increase the amount of grain being fed, which in this scenario would increase grain intake from 5.9 to 7.4 lbs. From a management standpoint, this potentially could be dangerous to increase grain that much overnight.
It is therefore recommended by NRC to provide hay free choice and allow horses to eat to their DE requirement. This provides the safest environment in which to increase DE intake during cold weather. In the cases of growing, working, thin or aged horses, an increase in grain may also be necessary, provided that this increase is done gradually. As with most scenarios in feeding horses, the best indicator is to monitor body condition.
Vitamin and/or mineral supplementation is not necessary during cold weather, and water should be provided free-choice. Most digestive disorders that occur during cold weather can be traced back to decreased water intake during that time. We can ensure consistent water intake during cold weather most easily by using trace mineralized salt blocks, electrolytes, or in some cases, by heating water to no more than 50 degrees F.
Finally, a study was conducted that looked at heat loss of horses during cold weather and the relationship to shelters, rugs and/or blankets. Results of that study indicated that heat loss during cold weather was reduced by 9, 18 and 26% by providing shelter, rugs or blankets, or shelters plus rugs/blankets, respectively.
If you have questions or want this addressed in seminar format, let me know.
J.Tim Potter, Ph.D., PAS
Area Specialized Agent-Equine
North Carolina State University
1450 Fairchild Road
Winston Salem, NC 27105