By Shelagh Niblock

For the horse owner, the onset of fall weather can signal the start of the search for storable forage before winter begins. Considerations such as forage type and storage form, nutritional content, palatability, and cost all become important.

Horses are classified as non-ruminant herbivores. They are adapted to eating plant fibre or forage sources such as pasture, or preserved forages such as hay, haylage or silage. Horses can utilize fibrous plant material very successfully through the hydrolyzation of simple carbohydrates and other nutrients in the stomach or foregut, and the fermentation by microbes of complex carbohydrate sources in the uniquely adapted hind gut. The energy derived from fibrous plant material is generated as a result of the fermentation of carbohydrates like cellulose by the natural microbes living in the hind gut of a horse.

Fermentation of these carbohydrates results in short chain fatty acids called volatile fatty acids (VFA). They are utilized by the horse as an excellent source of safe energy.

Horse are happiest when they can browse or forage for food for at least 10 to 15 hours per day. In summer, this can easily be provided through the feeding of fresh forages in the form of pasture. Weather prohibits the utilization of pasture as a forage source for a large part of the year in Canada. Canadian horse owners have a yearly objective of sourcing quality stored forage for our horses to consume in the coming winter months.  There are few things more satisfying for the horse owner than a successful search for winter feed that results in a barn full of good hay!

Forage preservation methods

Forages for horses are most commonly preserved for storage in the form of hay, haylage, or silage. The first step in preparing any kind of forage for preservation is the cutting and the subsequent wilting of the grass by the sun and air as it lies in the field. As forage is wilted the moisture level drops and the dry matter percent goes up. The amount of moisture present in the forage when baled will dictate whether the feed is stored as hay or ensiled as haylage or silage.

The first step in preparing forage for preservation is cutting it and allowing it to dry by the sun and air as it lies in the field. When baled, the amount of moisture in the forage will determine whether it is stored as hay, or ensiled as haylage or silage. Photo: Robin Duncan Photography

What defines hay?

Fresh grass when cut generally has a moisture content of at least 80 percent (resulting in a dry matter value or DM of 20 percent or less). Cut forage intended for hay must be allowed to dry in the field to a moisture level of not more than about 12 percent (88 percent DM). Hay that is baled with a moisture level in excess of 12 percent will result in bales that are heavy, and at risk of mould and heating. Heating can happen because the presence of sufficient water in the forage allows metabolic activity to continue, resulting in heat accumulation within the bale. The heat can get so high that spontaneous combustion and barn fires are the potential outcome. Always strive to buy hay for horses that is not more than approximately 12 percent moisture.

Related: Feeding Horses When Feed is Short

What about silage?

Ensiling forages is a practice where wilted or fresh cut grass is packed into an anaerobic environment. Anaerobic refers to an environment where no oxygen is present. The ensiling process allows the natural microbes on the grass to ferment the natural sugars in the grass (water soluble carbohydrates or WSC) to organic acids such as lactic acid or acetic acid. As the acids accumulate in the packed forage the pH drops, eventually arriving at a point where no more microbial activity can happen. This process generally takes about 21 days to complete. When the pH stops dropping, the ensiled feed is considered stable and ready for storage. In order to exclude the air from forages intended for ensiling, the bales are generally wrapped in plastic. Each bale is like a mini silo and has its own fermentation process. The quality of the forage that comes out of the bale is determined by the quality of the forage that went into the bale and the completeness of the ensiling process that was allowed to happen.

Forages baled too wet cannot achieve a low enough pH through the fermentation process and are therefore much more prone to spoilage and nutrient loss than drier bales. Less desirable end products of fermentation can result. An example of this is wet round bales that have an accumulation of butyric acid rather than lactic acid as a fermentation end product. Butyric acid doesn’t have as low a pH as lactic acid, and so it does not preserve the forage as well. It also has an unpleasant smell. Forages that are too moist at ensiling can become “compost-like” with pockets of rotten silage –  definitely not good feed for horses or cattle.

Forages that are baled too dry are difficult to compact enough to exclude all the oxygen, allowing aerobic (metabolic activity that needs oxygen) microbial activity, and just like conventional hay bales that are baled in excess of 12 percent moisture, heat generation to occur. Forage that is ensiled too dry is a fire risk and can have reduced feed quality due to heating within the bale.

The differences between haylage and silage

Haylage and silage are both ensiled forages, but the difference between them is moisture content. In general, haylage has a moisture content of between 15 percent to a maximum of 40 percent (60 to 85 percent DM). Silage has a moisture content of more than 40 percent (DM less than 60 percent). Both haylage and silage can be found in plastic-wrapped round bales. In silage with the higher moisture content, the preservation of the forage is as a result of the fermentation of the sugars in the grass under anaerobic conditions. This results in a pH drop. In general, a good grass silage in a round bale should have a pH of less than 5. In haylage, there isn’t sufficient moisture to allow for as much fermentation as in silage. The pH of a haylage round bale will be above 5 on a pH scale of 14. The preservation of the forage in haylage comes from the low moisture content which prohibits microbial growth.

It is possible to have a “hot spot” in either haylage or silage round bales. A hot spot is an area within the bale that is inconsistent with the rest of the bale. The feed in this spot may be completely rotten or poorly fermented. Hot spots are usually a result of contamination of the forage with either soil, animal manure, or dead animals such as mice that may have become caught up in the harvesting equipment. In the anaerobic conditions of a fermented feed, this can provide a potential health risk to horses because of the secondary bacteria that can grow. For this reason, clostridial organisms like botulism are a risk in feeding fermented feeds to horses.

Related: The How and Why of Soaking Hay

Botulism is the most sinister risk associated with feeding ensiled forages, and horses are more sensitive than any other animal species to the toxins produced by the botulism organism. Photo: Shutterstock/Sharon Kingston

Do all round bales contain ensiled forage? 

All round bales that are wrapped in plastic are either silage or haylage. The plastic is commonly white or light green, but can be black as well. The plastic wrap on the round bale provides the anaerobic environment necessary to allow the preservation of the forage through fermentation.

It is extremely important that all round bales fed to any livestock species be wrapped with sufficient layers of plastic. Bales that are not wrapped adequately are more likely to suffer tears and perforations of the plastic, allowing secondary bacterial growth. This can contribute to contamination of the bales with yeast, mould, mycotoxins, and spoilage bacteria.

As soon as the plastic is taken off an ensiled round bale, oxygen is admitted to the bale and spoilage is initiated. For this reason, round bales must be fed quickly once they are opened. Ensiled feed that is exposed to the air will heat and go mouldy very quickly.

Round bales that are wrapped in bale net only and no plastic are hay just like the conventional small, square bales. They should be stored in a dry place like any conventional hay bale. Yeast, mould, and mycotoxins are a risk if the hay was baled too wet or if it isn’t stored properly. Hay that is mouldy or heated should not be fed to horses.

Round bales wrapped in bale net with no plastic are the same as conventional small, square bales and should be stored in a dry place. Photo: Robin Duncan Photography

What about preservatives for hay or ensiled feed?

Preservatives like propionic acid can be used to speed up the drop in pH in ensiled forages and prohibit microbial growth in hay that is higher in moisture than ideal. Although propionic acid is safe for horses, it is expensive and so not routinely used by growers. Inoculants such as bacterial cultures of lactic acid-forming bacteria are used by some growers to facilitate a good fermentation in ensiled forage. Again, they are safe for horses but expensive, and will increase the cost of the feed.

Related: Mycotoxins in the Equine Environment

What happens if forages are contaminated by soil or manure?

Any stored forage – whether hay, haylage, or silage – will not be improved by contamination with soil or manure. Manure applications utilized as fertilizer on forages intended for horses can reduce the palatability of the resulting feed unless applied appropriately. Soils coming from mud on cut grass, or cutting grass too close to the soil, will contaminate the feed, make hay dusty, and reduce ensiled feed quality. Both manure and soil contain organisms such as clostridia and coliforms, which are bacteria that contribute to poor fermentation. Botulism is caused by a clostridial organism that will grow readily in an ensiled round bale, producing a toxin that will kill a horse.

Cost of round bales versus hay: Which is more economical?

Frequently, the rationale for feeding ensiled forage to horses is cost. If a comparison of the cost of a 1,000 lb wrapped round bale and the cost of 1,000 lb of grass hay is reviewed, the hay often appears more expensive. Remember, though, that the wrapped round bale is probably at least 50 percent water, whereas the hay is a maximum of 10 percent water. In order to truly calculate the value of a stored forage, it is important to know its moisture content so you can calculate how much dry matter you are buying. It is likely that based on the cost per unit of dry matter, the hay is better value. The most important tool for good forage-buying decisions is a forage analysis completed in a recognized laboratory. At the very least, a lab analysis will tell you how much water you are buying. It isn’t possible to accurately assess the value of the feed for your horse until you have proof of the nutritional analysis of it.

Nutritional characteristics

The nutritional characteristics of ensiled forage are similar to those of hay with some exceptions. Ensiled forage is preserved through the fermentation of the natural sugars in the grass to fermentation acids, and so water soluble carbohydrates (WSC) can be lower in ensiled forages than in hay coming off the same field.

There is research in both ruminants and horses suggesting that ensiled feed can have a small increase in digestibility, but the significance of this is largely determined by the nutritional content of the fresh cut grass that was ensiled. Protein quality can suffer in an ensiled forage. Growing horses and performance horses could be negatively impacted by this, and so only the highest quality forage should be provided for them. 

The dry, long stem grass found in hay encourages more chewing compared to wetter forages. Chewing forages encourages grinding of the feed before it reaches the stomach. Well-chewed forage has improved nutrient digestibility. Chewing also encourages saliva production, an important aspect of the buffering capacity of the equine foregut.

Horses that are fed wetter forages free-choice can have amazingly high intakes. Wetter forages can be easier to eat and increases in total feed intake can be an outcome of feeding ensiled forages. If you have an overweight eating machine at home, be cautious about leaving him alone with a round bale offered free-choice.

Health considerations

Unfortunately, ensiled forages do have risks associated with them. Yeast, moulds, mycotoxins, and spoilage bacteria are a risk in any ensiled forage, but particularly in plastic-wrapped round bales. Haylage that is mouldy will carry an increased risk of respiratory problems for the horses consuming it. Wrapped haylage or silage round bales usually have to be stored outside, leaving them at greater risk for damage from birds and the weather.

The most insidious risk associated with feeding ensiled forages is that of botulism. Horses are more sensitive than any other animal species to the toxins produced by the botulism organism, and death for the horse can be swift if contaminated forage is consumed. It is a reality that any round bale has the potential to be the carrier of botulism, no matter how well it feeds out. If feeding plastic wrapped round bale forage to horses, be extremely careful to dispose of uneaten feed before it heats, and avoid any bale with damaged plastic wrap.

Conclusion

When choosing what kind of conserved forage to feed your horse, it is useful to consider the following facts:

• The need for a hay analysis before making any kind of buying decision. The moisture content of the forage is a critical quality factor, especially if you are considering round bale haylage as an option. Forage that is ensiled too wet is not appropriate for horses. Feeding wrapped round bales can be more costly than feeding conventional hay. It is important to calculate the cost per unit of dry matter of both feeds to evaluate them properly. 
• The need for forage that is free of weeds, soil, or manure contamination. This becomes a critical quality parameter when feeding ensiled forages to horses. Contaminated ensiled forage can lead to disease conditions such as botulism in horses.
• The kind of storage available. For many horse owners, big bale hay or round bales are simply not practical from a storage and management perspective.
• Introduce feed changes gradually. Always introduce new forage choices to your horse gradually to permit the digestive tract time to adapt slowly.  

A good supply of quality hay is essential to keep horses and their owners happy during the long, cold Canadian winters.Photo: Shutterstock/Shannon Jordan

If you have any questions about choosing the appropriate forage for your horse, consult with an equine nutritionist or your veterinarian before buying anything. Timely questions can be invaluable in your quest to provide your horse with the best feed possible.

Related: How to Interpret Your Hay Test

More by Shelagh Niblock

Reference: Review: Feeding conserved forage to horses: Recent advances and recommendations; by P.A. Harris, A.D. Ellis, M.J. Fradinho, et al.

Main photo: Shutterstock/Cornfield