Nutritional Suggestions for Feeding Your Horse in the Winter

by: Daniel J. Burke, Ph.D., Director of Tribute Equine Nutrition at Kalmbach Feeds

What can you do to keep your horse comfortable and in good body condition in the winter? 

The most important management task you can do for your horse is to ensure he has clean, acceptable water at all times!! Water below 45° will reduce the horse's voluntary intake and can lead to colic and/or impaction.

Heated buckets or adding warm water to his bucket can remedy water that is too cold.

How does cold weather affect your horse?

We first have to understand what is happening to the horse's body, then the nutritional part will make sense.

THERMOREGULATION is the fancy term for how the horse maintains his optimal internal temperature despite fluctuations in external temperature. The horse, like humans, naturally try to keep their body core temperature within a certain range.

The temperature the animal actually feels, given air movement, humidity, radiation, etc. is called EFFECTIVE AMBIENT TEMPERATURE or E.A.T. This is similar to what we think of as "wind chill."

FACTORS AFFECTING E.A.T.:

• Thermal radiation - heat from the sun and earth
• Humidity - more humidity in the winter makes the horse feel colder
• Air movement - more wind in the winter makes the horse feel colder
• Contact surfaces - are they in contact with cold surfaces like the frozen ground

The horse will try to stay warm by doing certain things, called:

Behavioral thermoregulation:

• Basking in sunlight
• Posture - tucking tail, lowering head, facing away from the wind
• Exercise
• Huddling

In addition, the horse's body also makes internal changes to try to stay warm, called: 

Physiological thermoregulation:

• constricting blood vessels to keep the warm blood deeper in the body; one of the reasons frostbite occurs
• shivering to generate body heat - costs a lot of calories - if the horse is shivering, action needs to be taken to warm him up (shelter, blanket, etc.)
• hair will be standing up - increases the insulation from still air within the haircoat - a horse with a heavy winter coat can withstand low temperatures better than one with a shorter coat as the hair traps still air next to the skin, which acts as a great insulation layer
• the horse's metabolic rate goes up to generate heat - loses a lot of calories

Feeding program 

The major nutrient needed to help the horse deal with all the heat loss is CALORIES (energy). If he does not get enough calories to replace the ones lost to the environment, he will lose weight. None of the other nutrients increase in significant amounts.

When do we start to worry about the environment negatively affecting the horse? The Lower Critical Temperature (LCT) is the temperature at which the horse must start the above behaviors and physical responses to maintain body temperature. NRC 2007 suggests that the LCTs for different ages of horse is:

So how does this translate to feeding the horse in winter? The chart below shows the increase in calories (Mcal = 1,000 kcal) and % for certain temperature decreases BELOW the LCT.

For example, an 1,100 pound horse normally would require 16.7 Mcal (or 16,700 kcal) per day to maintain his current weight. If the E.A.T. gets to -5°F, he would need an extra 4.2 Mcal of energy per day, a 25.1% increase. 

In general, hay has about 1 Mcal/pound. Thus, a little mroe than 4 pounds more hay per day would provide the extra calories needed in the above example. Grain mixes or concentrates will typically contain 1.3 to 1.6 Mcal per pound, so about 3 pounds of grain would meet the extra caloric need.

Higher fat supplements (20-100% fat) will contain 1.9 to near Mcal per pound, respectively. In the example, 2 pounds of a 20% fat supplement or 1 pound of 100% fat or oil will meet the need.

"HEATING" feeds - there is a common misconception that certain feeds, like corn, actually warm the horse up. This is NOT true. Corn is high in calories, so it can help a horse maintain weight in cold weather, but the calories come primarily from starch, which can contribute to many metabolic issues, especially at high intake levels.

Theoretically, feeds high in fiber, like hay, may generate more heat as they are digested by fermentation in the horse's hindgut. Whether fermentation provides enough energy to truly affect the horse's body temperature or comfort is not known.

"I need to get my horse fat to get through the winter"

Many horse owners try to get their horses fat going in to winter, correctly thinking the fat would help insulate him from the cold. BUT, to accomplish this, a horse would need to gain 50 - 100 pounds for winter, then LOSE it for summer!

Forcing large fluctuations in body weight by making large diet changes as seasons change is not at all healthy for the horse. Significant negative metabolic effects can occur when a horse is heavy (body score 7 or above), like insulin resistance, and potentially, founder and/or equine metabolic syndrome.

We suggest adjusting the feed intake according to the temperature - the colder it is, the more feed the horse would need (refer to chart above). If it warms up, you can cut back. Of course, make the changes gradually, especially when INCREASING intake. Watch the weather - if it's going to get cold, slowly add more hay, concentrate or fat. A very safe way to add lots of calories without adding much volume or risk is to use a fat supplement in addition to the horse's regular grain or concentrate.

The cost in feed to put an extra 100 pounds on a horse will exceed $100. The cost of a good turnout blanket is about $100 and will last more than one year. It is MUCH less expensive and healthier for the horse with a poor haircoat to wear a turnout blanket to help retain body heat than to gain and lose dozens of pounds every year throughout his life.

What Can I Do?

• ALWAYS provide acceptable water (≥45°F)
• Provide shelter from elements (loafing shed, stall...) - Assure ventilation!!!!!
• Increase feed intake as dictated by the weather- hay, high fiber concentrate and/or fat, if possible. 
• Turnout blanket
• Relax - horses handle cold MUCH BETTER than excessive heat...main issue is weight loss. Watch body condition and don't let them get too fat. If you feel the horse is losing weight, gradually adjust their calorie intake as described above.

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