As pasture growth slows and turnout changes, hay often becomes the main source of forage for horses during winter. That makes the quality, nutritional value and cleanliness of your hay more important than ever.

The right hay can help maintain body condition, provide energy during cold weather and support normal digestive function. Poor-quality, overly dusty or moldy hay, on the other hand, can create nutritional and respiratory concerns.

TL;DR: Hay is more than something that fills your horse’s feeder. During winter, it may provide most or all of the forage in the diet, so its nutritional value and physical quality matter. A forage analysis can reveal what you cannot see, while regular inspection can help you identify dust, mold, poor storage or a mismatch between the hay and your horse’s needs.

Why Does Hay Become the Foundation of the Winter Diet?

For many horses, winter means less access to fresh pasture and more time eating stored forage. Horses are designed to consume forage as a major part of their diet, and quality hay can provide much of the energy and nutrients an adult horse needs.

Forage also has an important role in keeping horses warm. Fermentation of fiber in the hindgut produces heat, which is one reason increasing forage can be useful when temperatures drop.

That does not mean every horse should simply receive unlimited hay. An easy keeper may gain weight on energy-dense forage, while an older horse, hard keeper, growing horse or horse in heavier work may need more nutritional support.

Winter feeding starts with looking at the horse, not just the hay pile.

Is Hay Quality More Important Than Quantity?

Both matter, but adding more hay does not necessarily correct a nutritional shortfall.

A mature, stemmy hay may contain considerably different levels of protein, energy and fiber than a leafy, less mature forage. Plant maturity has a major influence on forage quality. As plants mature, fiber increases and digestibility can decrease.

That is why two bales that look broadly similar can provide very different nutrition.

Good hay should generally be:

• Clean and free of visible mold
• Free of excessive dust
• Pleasant smelling rather than musty
• Reasonably leafy for the type of forage
• Free of toxic plants and excessive foreign material
• Stored in a way that protects it from moisture

Appearance can provide useful clues, but it cannot tell you the complete nutritional picture. Laboratory testing is the better way to understand what your horse is actually consuming.

How Does Stored Hay Differ From Pasture?

Moving from pasture to hay changes more than the texture of your horse’s meals.

Fresh pasture contains a different mix of moisture, carbohydrates, vitamins and other nutrients than dried, stored forage. Some nutrients can decline during harvesting and storage, while the nutritional profile of the forage is also affected by plant species, maturity, growing conditions and harvesting practices.

That means you should not assume that hay made from the same field automatically provides exactly the same nutrition your horse received while grazing.

For horses that spend much of the winter on hay, a forage analysis can help identify whether the diet needs additional nutritional support.

A previous Equine Wellness guide on hay analysis offers another useful starting point for understanding forage quality and testing.

What Should You Look for on a Hay Analysis?

A hay analysis can take some of the guesswork out of winter feeding.

Depending on the horse and the reason for testing, useful information may include:

Moisture: Helps assess storage quality and the risk of spoilage.

Crude protein: Provides an estimate of the forage’s protein content.

Energy: Helps determine whether the hay provides enough calories for the individual horse.

ADF and NDF: These fiber measurements provide information about digestibility and intake characteristics.

Calcium and phosphorus: Important when assessing the mineral balance of the overall diet.

Water-soluble carbohydrates, starch and NSC: Particularly useful when selecting forage for horses that need careful carbohydrate management.

The University of Minnesota Extension recommends requesting an equine-specific analysis and using a representative forage sample. Their guidance also notes that hay analysis can help identify nutritional deficiencies and support more precise feeding decisions.

For a horse with metabolic concerns, unexplained weight changes or specialized nutritional requirements, discuss the results with your veterinarian or an equine nutrition professional rather than choosing a hay solely from a single number on the report.

Could Dust or Mold in Hay Affect Respiratory Health?

Yes. Hay quality is about more than nutrition.

Dust and mold spores can become airborne when hay is moved, shaken or eaten. Horses exposed to dusty or moldy forage can develop respiratory irritation, and susceptible horses may be particularly affected.

Before feeding a new bale, look beyond the outside surface. Check the center of the bale for:

• Musty or unusual odors
• Visible mold
• Excessive dust
• Damp or unusually warm areas
• Discoloration that suggests spoilage

Moldy hay should not be fed to horses. Mold spores can contribute to respiratory problems, and some molds can also produce toxins under the right conditions.

Storage matters, too. Hay that is exposed to moisture has a greater risk of mold growth, so keep stored forage protected from rain, ground moisture and leaks.

If your horse develops a persistent cough, nasal discharge, increased breathing effort or reduced exercise tolerance, do not assume dusty hay is the only possible cause. Respiratory signs warrant veterinary evaluation.

Can Slow Feeding Help During Winter?

A slow-feeding system can make sense for horses that finish their hay quickly or spend long periods without forage.

Rather than simply increasing the total amount of hay, a suitable slow feeder can extend feeding time and encourage a more gradual intake. It may also help reduce hay waste.

The goal is not to make a horse work unnecessarily hard for every mouthful. Choose a system that allows the horse to eat comfortably and provides appropriate access to forage.

Slow feeding can be particularly useful during winter because pasture grazing opportunities may be limited. A horse that normally spends much of the day moving between patches of grass may have fewer natural feeding opportunities when confined or kept on dry lots.

How Do You Match Hay to the Individual Horse?

There is no single “best” hay for every horse.

Consider your horse’s:

• Age
• Body condition
• Workload
• Metabolic health
• Growth or reproductive status
• Dental health
• Digestive health
• Energy requirements
• Ability to chew and consume long-stem forage

A mature grass hay may be an excellent choice for an easy keeper, while a horse struggling to maintain weight may need a more nutrient-dense forage or additional calories. Legume hays such as alfalfa generally provide more energy, protein and calcium than many grass hays, so the appropriate choice depends on the complete diet and the horse’s requirements.

For horses sensitive to dietary sugar and starch, the carbohydrate content of the forage deserves particular attention. Testing is much more reliable than judging carbohydrate levels by appearance alone.

Dental health deserves consideration, too. A horse that struggles to chew long-stem hay may need a different forage format or feeding strategy, particularly as he ages.

A Simple Winter Hay Check

Before settling into your winter feeding routine, take a few minutes to assess the forage and the horse.

Check the hay: Does it smell clean? Is it free of visible mold and excessive dust?

Check the bale: Has it been stored somewhere dry and protected from moisture?

Check the analysis: Do you know its energy, protein, fiber and carbohydrate levels?

Check the horse: Is body condition stable? Is your horse eating comfortably and maintaining normal manure output?

Check the environment: Is your horse spending more time indoors, where dust and poor ventilation can compound respiratory challenges?

Check the feeding system: Is hay available often enough to suit your horse’s management needs, and could a slow feeder reduce long gaps between meals?

These small observations can reveal when a winter feeding program needs adjustment.

The Takeaway

Your horse’s hay can tell you a surprising amount about his winter health, but only if you look beyond the bale itself.

Quality forage provides the foundation for a winter diet, while hay analysis helps reveal nutritional differences that cannot be seen by eye. Clean, properly stored hay also matters for respiratory health, particularly when horses spend more time indoors.

Most importantly, match the forage to the individual horse. A hay that works beautifully for one horse may be too rich, too low in energy or otherwise unsuitable for another.

For more guidance on preparing your horse for the colder months, read Winterizing Your Horse Naturally, which covers forage, hydration, shelter, turnout and body-condition monitoring.

Frequently Asked Questions

How much hay does a horse need in winter?

The amount depends on body weight, hay quality, metabolism, workload, age and environmental conditions. Many horses consume roughly 2% of body weight in forage daily, but individual requirements can vary. Cold weather can increase energy needs, so body condition should be monitored regularly.

Should I have my horse’s hay tested?

Yes, particularly when hay is the primary forage source or when your horse has specific nutritional requirements. A hay analysis can provide information about energy, protein, fiber, minerals and carbohydrates that cannot be determined reliably by appearance alone.

Can horses eat dusty hay?

Dusty hay is best avoided. Dust and mold particles can irritate the respiratory tract, and horses with respiratory disease may be especially sensitive. If your horse is coughing or showing other respiratory signs, consult your veterinarian.

Does a horse need more hay when it gets cold?

Sometimes. Cold temperatures can increase energy requirements, and forage fermentation produces heat. However, the appropriate amount depends on the individual horse, the hay’s nutritional value, body condition and access to shelter.