Haylage is grass or other forage that has been partially dried and then sealed in airtight wrapping to ferment. It sits between traditional dry hay and wet silage on the moisture spectrum, with a dry matter content of roughly 40% to 60%. That means it retains more moisture than hay (which is dried down to 14% to 18% moisture) but far less than high-moisture silage. This middle ground gives haylage some distinct advantages in terms of nutrient preservation, flexibility during harvest, and suitability for animals with respiratory sensitivities.
How Haylage Differs From Hay and Silage
The easiest way to understand haylage is to picture a moisture scale. Fresh-cut forage starts at 75% to 80% moisture. To make traditional hay, you dry it in the field until moisture drops to roughly 14% to 18%. To make high-moisture silage, you chop and store it at 70% moisture or higher. Haylage lands in between: you wilt the forage in the field until it reaches about 35% to 60% moisture, then bale and wrap it before it dries further.
This shorter drying window is one of haylage’s biggest practical benefits. Hay needs several consecutive dry days to cure properly in the field, and rain at the wrong moment can ruin an entire cutting. Haylage only needs to wilt for a day or so before baling, which makes it far more forgiving in climates with unpredictable weather. Farmers in the UK, northern Europe, and parts of the northeastern United States rely heavily on haylage for exactly this reason.
The Fermentation Process
Once a haylage bale is wrapped in plastic, the environment inside becomes oxygen-free. Beneficial bacteria naturally present on the forage begin converting plant sugars into lactic acid, dropping the pH and preserving the forage in much the same way sauerkraut or pickles are preserved. This is the same basic process used for silage, just with drier starting material.
The target is a pH low enough to prevent harmful organisms from growing. If the pH stays above about 4.6, dangerous bacteria like Clostridium botulinum (which causes botulism) can thrive in the oxygen-free environment. Proper wilting is critical here. Forage that’s too wet won’t acidify correctly, and forage contaminated with soil or animal remains introduces more of these harmful bacteria in the first place. Clean, well-wilted forage wrapped tightly is the foundation of safe haylage.
Nutritional Profile
Haylage generally retains more nutrients than field-dried hay because the shorter drying time means less leaf shatter. Leaves are the most nutritious part of the plant, and every time a drying hay bale is raked or turned, fragile leaves break off and stay in the field. With haylage, much of that leaf material stays in the bale.
A study comparing alfalfa haylage to alfalfa hay and meadow hay found that alfalfa haylage had a crude protein content of about 139 grams per kilogram of dry matter, similar to alfalfa hay (127 to 135 g/kg) and substantially higher than meadow hay (79 to 88 g/kg). Metabolizable energy levels were comparable across all three forage types. The protein advantage of haylage over meadow hay largely reflects the forage species rather than the preservation method, but the reduced leaf loss during haylage production helps preserve whatever nutritional value the plant offers.
Haylage also tends to be more palatable than dry hay. The slight fermentation gives it a mild, sweet smell that most horses and cattle find appealing, and the higher moisture content makes it softer and easier to chew.
Why Horse Owners Use Haylage
Haylage has become especially popular in the horse world for two reasons: dust and sugar content. Dry hay, even good-quality hay, contains fungal spores and fine dust particles that can trigger respiratory problems in horses. Haylage’s higher moisture traps those particles, making it a common choice for horses with recurrent airway inflammation or heaves.
Sugar content is another consideration. Horses prone to laminitis or metabolic conditions like polysaccharide storage myopathy (PSSM) need diets low in nonstructural carbohydrates, ideally below 10% to 12% of the total ration. The fermentation process in haylage uses up some of the plant’s water-soluble carbohydrates, which can lower overall sugar levels compared to the same forage preserved as dry hay. However, the reduction isn’t always dramatic or predictable, so testing individual batches is the only reliable way to know the actual sugar content of a specific haylage bale.
Wrapping and Storage
Proper wrapping is the single most important factor in haylage quality. The goal is to completely exclude oxygen so fermentation proceeds correctly and mold can’t grow. Research from the University of Wisconsin found that bales need at least 6 mils (six thousandths of an inch) of total plastic thickness to produce good haylage, with 8 mils being the safer target. Importantly, total plastic thickness matters more than the number of wrapping layers. Four layers of 1.5-mil plastic work just as well as six layers of 1-mil plastic, and using fewer, thicker layers saves time and labor.
Bales should be wrapped within 24 hours of baling. When wrapped with adequate plastic thickness, internal temperatures drop to ambient levels within eight to nine days, a sign that the forage has stabilized. Any puncture in the wrapping, whether from rodents, birds, or rough handling, lets oxygen in and creates a pocket where mold and harmful bacteria can grow. Inspecting wrapped bales regularly and patching holes with tape designed for silage wrap is standard practice.
Storage location matters too. Bales stored directly on the ground or in areas with heavy rodent activity are more likely to develop damage. Placing bales on a hard, well-drained surface and keeping vegetation trimmed around the storage area reduces the risk of punctures.
Shelf Life After Opening
Once you break the seal on a haylage bale, the clock starts ticking. Oxygen re-enters the forage, and spoilage organisms begin growing. How fast this happens depends largely on temperature. In summer heat, an opened bale should be used within one week. During spring and fall, you have roughly two weeks. In winter, the cooler temperatures slow spoilage enough to give you about four weeks.
This timeline means you need to match bale size to your feeding rate. If you’re feeding a single horse, a large round bale of haylage may spoil before you can use it all in warm weather. Smaller square bales or individually wrapped portions can be more practical for smaller operations. Visible mold on haylage should always be treated seriously, particularly with horses, since moldy haylage carries a higher botulism risk than moldy dry hay due to the anaerobic conditions inside the bale.
Risks to Watch For
The most serious risk associated with haylage is botulism. Clostridium botulinum spores are naturally present in soil, and if soil gets into the forage during harvesting, those spores can multiply in the oxygen-free, high-moisture environment inside a wrapped bale. The toxin they produce is lethal in small amounts, and horses are particularly sensitive. Bales that smell foul, have visible areas of dark slime, or were clearly contaminated with soil or animal carcasses during baling should never be fed.
Good haylage smells mildly sweet or slightly vinegary. A strong, unpleasant odor is a clear warning sign. Forage that was baled too wet (above 60% moisture), wrapped too late, or stored with damaged plastic is more likely to harbor dangerous bacteria. Some horse owners vaccinate against botulism as an added precaution, especially in regions where the disease is more common.
Mold is the other major concern. Unlike dry hay, where you can sometimes shake out a dusty flake and the horse will sort around it, mold in haylage can penetrate deeply without being visible on the surface. If any portion of a haylage bale looks or smells off, discarding the entire bale is the safer choice.