How Much Hay Does Your Horse Really Need to Stay Warm?
By Annie Emery
People often simplify winter feeding advice to just one idea: “It’s cold, so give more hay.”
There is some truth to this, but the real answer is more complex. Knowing how and why cold weather changes calorie needs can help you support your horse without wasting hay, overfeeding, or causing weight gain.
This article offers a clear, evidence-based look at what really keeps horses warm and how to know when extra forage is needed.
Why Horses Need More Calories in Winter
Horses use energy to keep their bodies warm. When the weather gets colder than they are used to, they need more calories just to stay warm.
So where do those extra calories and that internal heat come from?
Forage.
When fiber ferments in the hindgut, it produces heat that warms the horse from the inside. This is why hay and fiber, not corn and oat-based grain, is the key to winter feeding. Horses that do not get enough forage in cold weather may lose weight or start to shiver as their bodies use up reserves.
However, some horses really do need more hay in winter, while others do not.
Context Matters: Which Horses Need More Forage?
Before you add more hay, look at the whole situation:
Living environment: 24/7 turnout vs. part-time stabling
Weather exposure: wind, rain, snow, or dry cold
Shelter access
Blanketing
Coat length or clipped coats
Age and metabolic function
Body condition score (BCS)
Young horses and older horses often need extra support. Horses that are hard to keep weight on, those with thin coats, and those living outside in windy or wet weather usually need more calories. Yes, young horses get colder, faster!
On the other hand, a horse at a healthy weight (BCS 5–6.5) that stays in a barn overnight, wears the right blankets, and is sheltered from the weather usually does not need a big increase in hay every time it gets colder.
Giving too much hay to a horse that is already overweight can make obesity worse, which is a risk for metabolic disease. It also adds extra calories the horse does not need, and may waste hay costing you money!
Understanding the Lower Critical Temperature (LCT)
The Lower Critical Temperature (LCT) is the temperature at which a horse has to use extra energy to keep warm.
LCT varies widely depending on the horse:
Acclimated horses with good winter coats: ~18°F
Clipped or thin-coated horses: may begin using extra energy at ~40°F
Young or older horses: may reach LCT sooner
Horses coming from warm climates: require an adaptation period
Wet, windy conditions can make 35°F feel colder than a dry 10°F
It takes about 21 days for a horse to get used to colder weather. During this time, they might need a little more forage.
When temperatures drop below a horse’s LCT, their energy needs go up. This often means they need 1 to 3 more pounds of hay per day, depending on the horse. That’s why one-size-fits-all feeding advice does not work.
Nutrition is never the same for every horse.
Why Forage Creates Warmth (and Grain Doesn’t)
Fiber fermentation in the hindgut produces heat.
Starch digestion in the small intestine does not.
This is why:
Hay
Beet pulp
Soybean hulls
Wheat middlings
Alfalfa
Flax-based forage feeds
These are the best sources of energy for horses in winter.
Sweet feeds, corn, and oat-based concentrates do not help horses stay warm. They can also cause problems, especially for horses with metabolic issues or those prone to ulcers.
Does Alfalfa Warm the Horse?
No research shows that alfalfa keeps horses warmer than grass hay. The myth comes from the fact that alfalfa has more protein and calories.
If your horse already thrives on alfalfa, that’s fine—continue.
For most horses, good grass hay is enough. Being consistent is more important than the type of hay.
Transitioning Hay and Avoiding Digestive Stress
Try not to change your horse’s forage suddenly.
Transition new hay over 5–7 days to introduce new hay over 5 to 7 days to help the hindgut adjust and prevent stomach problems. It is more likely to cause digestive issues than a cold front.
Monitoring Body Condition Through Winter
Hay from late winter can have less nutrition, especially if it is from older cuttings.
Monitor your horse’s:
Body Condition Score
Topline
Hoof quality
Overall energy
Check your horse’s BCS at least once a month, or even every two weeks if possible. Making small changes early can help you avoid bigger problems later in March or April.
If your horse has metabolic syndrome, PSSM, RER, MFM, fecal water syndrome, or other complex health issues, it’s best to get a professional review.
The Value of Testing Your Hay
Even if you cannot switch hay sources, testing your hay still gives you useful information.
I often find hay that looks poor but tests surprisingly well, and sometimes the opposite is true.
Hay testing helps determine:
Whether protein or calorie supplementation is necessary
If mineral balance adjustments are needed
How to choose the right concentrate
Whether a horse’s subtle symptoms reflect dietary trends
For about $36, hay testing is one of the most cost-effective tools for making winter feeding decisions.
Building a Simple, Effective Winter Plan
A winter nutrition plan does not have to be complicated. Focus on these basics:
Long-stem forage
A balanced pelleted concentrate (appropriate for your horse)
Salt (2 tablespoons/day minimum)
Warm, clean water
Supplements can be helpful, but they are not a substitute for the basics.
Pay close attention to your horse. Make small changes as needed, and if something seems wrong, ask a qualified expert for help.