Nutritional Tips for Winterizing Your Horse

What can you do to keep your horse comfortable and in good body condition in the winter?  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 tp 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 EFFECTIVE AMBIENT TEMPERATURE:

  1. Thermal radiation - heat from the sun and earth.
  2. Humidity – more humidity in the winter makes the horse feel colder.
  3. Air movement - more wind in the winter makes the horse feel colder..
  4. 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”like :

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

The horse’s body also makes internal changes to try to stay warm, called “Physiological thermoregulation”. These include:

  • constricting blood vessels to keep the warm blood deeper in the body; one of the reasons frost-bite occurs
  • shivering to generate body heat – loses a lot of calories
  • hair will standing up – increases the insulation from still air within the haircoat
  • the horse’s metabolic rate goes up to generate heat – loses a lot of calories

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. It is thought that the LCT for the horse is:
With Dry winter coat ~ 18 degrees F
With Wet or summer coats ~ 59 degrees F

So how does this translate to feeding the horse in winter?? The chart below shows the increase in calories needed for certain conditions.

Effect of Cold Temperatures on Metabolizable Energy Needs​

EFFECTIVE AMBIENT TEMP (F) WIND SPEED (mph) INCREASE IN ENERGY NEED (%)
68 0 0
30 0 23
10 0 47
10 10 66

The lower the E.A.T., the faster the horse looses heat to the environment; heat = CALORIES!!!!
What Can I Do?

  • Provide acceptable water (> 45 deg. F).
  • Provide shelter from elements (loafing shed, stall…).   Assure ventilation!!!!!!!!
  • Increase feed intake – hay and/or fat, if possible. Calorie needs may increase 20% or more depending on exposure to elements = maybe 20% more grain or equivalent calories from fat.
  • Turnout blanket.

….BUT

  • What About Cost?
  • What About Metabolic Effects??

Many horse owners try to get their horses fat going in to winter. A horse would need to gain 50 – 100# for winter, then LOSE it for summer!

Many diet changes as seasons change is not at all healthy for the horse. In addition, significant negative metabolic effects occur when a horse is heavy (body score 7 or above), like insulin resistance and, potentially, founder and/or equine metabolic syndrome.

Below is a chart showing how much it would cost for a horse to gain 100 pounds:


Cost of a good turnout blanket is about $100.00. It is MUCH less expensive and healthier for the horse to wear a turnout blanket to help retain body heat than to gain and lose dozens of pounds every year throughout his life.

We suggest adjusting the feed intake according to the temperature – the colder it is, the more feed the horse would need. 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 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.

Relax – horse’s 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, adjust their calorie intake as described above.

D.J. Burke, Ph.D.