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What’s the difference between hay and haylage?

Here’s a quick guide to both:

Hay is grass that’s cut at a mature stage before being left to completely dry out. Because of this, it has a very low moisture content. During the drying process, nutrients in the grass can be lost. The more mature nature of the grass, along with the loss of nutrients during the drying process, generally make it a very low-calorie snack. As a horse owner, you won’t need to worry about weight gain when using hay as a bonus feed.

Haylage is grass that’s been cut at an earlier stage of growth than hay. And instead of being left to dry, haylage is wilted. This means it has a much higher moisture content. Because it’s not put through a long drying process, haylage is able to retain more of its nutrients – particularly protein.

The fundamental difference between hay and haylage is the way that the grass is conserved. Hay is cut when grass is mature and left to dry in the field before being baled and stored. To conserve hay and prevent it from spoiling or going mouldy, the grass needs to be sufficiently dry before baling. Typically hay will be 85% or above dry matter which relies on good weather conditions to achieve – not always easy in the UK! Hay of insufficient dry matter will not store well and will be very likely to go mouldy making it unsuitable to feed.

Haylage tends to be cut earlier in the season and is left to wilt for a shorter period of time in the field before being baled and wrapped in several layers of plastic. The difference between haylage and hay is that, whilst the conservation of hay relies on the removal of moisture, the conservation of haylage relies on the exclusion of oxygen which prevents mould growth. Haylage is typically between 50 and 70% dry matter.

There seems to be an increasing trend to produce drier haylage which is more accurately termed ‘wrapped hay’ as the dry matter is closer to that of hay. Caution has to be taken with very dry haylage when wrapping as dry, coarse material may result in more air pockets in the bale and a bale that is more difficult to wrap without puncturing the plastic. Both of these factors can mean that very dry haylage is more susceptible to higher mould counts or becoming spoiled during storage as the higher levels of oxygen increases the opportunity for mould growth.

Another difference between hay and haylage which confuses many people is how much to feed. Due to a greater amount of moisture in haylage you actually need to feed more haylage by weight than hay to provide the same amount of dry matter. For example, a 500kg horse that needed 10kg of forage on a dry matter basis daily would require 11.8kg of hay as fed assuming it was 85% dry matter and 16.7kg of haylage as fed assuming it was 60% dry matter in order to provide this. Knowing how much moisture your forage contains by analysis is key for working this out!

Is haylage better than hay?

Any nutritional differences between hay and haylage are predominantly determined by the grass type and age of maturity when harvested rather than the actual conservation methods. The table below shows the differences between hay and haylage when made from grasses cut within the same field at the same time to show the differences due to the conservation method.

Preference of horses for grass conserved as hay, haylage or silage C.E. Muller ∗,  *Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences

As can be seen from the table, some nutrients don’t vary much as their levels are determined more by the grass species than the conservation technique. This would include ash which is an analysis of the inorganic materials such as minerals, as well as the NDF which is a measure of fibre. What may be surprising is the difference in WSC. This stands for water soluble carbohydrate and is a measure of the simple sugars plus fructan.

  The haylage in the table above has been very carefully conserved and has sufficient moisture to ensure that some fermentation has occurred. This uses up the sugar and converts it to another form of energy called volatile fatty acids which reduces the sugar level. In practice many of the haylages that are tested via Dengie’s forage analysis service have very similar WSC levels to hay, especially if they are more like a wrapped hay with a higher dry matter.

Another thing to consider when weighing up whether haylage is better than hay is respiratory health. Hay is a larger source of respirable particles compared to haylage. Respirable particles are very small particles that are invisible to the naked eye and are a combination of things that could potentially be harmful to your horse’s respiratory health including mould spores and bacteria. Another option for overcoming this issue is to steam hay using a hay steamer e.g. Haygain, or a high temperature dried forage replacer such as Dengie Hi-Fi Senior or Pure Grass as high temperature drying produces a consistently clean forage source.

When can I feed this year’s hay or haylage?

A common question to the Dengie Feedline is how soon can I feed this year’s hay or haylage? When it comes to this year’s hay once it is baled and stored the answer is you can introduce it straight away as long as there is no heating in the bales.

Do bear in mind that the nutritional value of the hay will be greatest just after harvest, nutrients such as vitamins will decline over time. When it comes to haylage it is a bit longer – usually around 6 weeks or longer. This is because it takes time for the fermentation process to take place which then ensures it is properly conserved.  Whichever forage you use and whenever you choose to introduce it the key advice is to remember that any change between batches of forage constitutes a dietary change and should be done gradually over the period of a couple of weeks by ideally mixing old and new forage together.

Can I feed hay or haylage as the sole diet or does haylage and hay lose nutritional value with age?

Generally, UK pasture and therefore forage lacks the trace minerals copper, selenium and zinc. Conserved forage like hay or haylage also loses vitamins, for example vitamin E which is usually abundant in grass, very quickly post-harvest. Whilst hay and haylage alone may provide enough calories for many horses and ponies it should be supplemented with a broad-spectrum vitamin and mineral supplement, balancer or fortified feed.

One myth when it comes to feeding hay is that last year’s hay is safer for a laminitis prone horse or pony. Post-cutting and baling when the grass has finished respiring there will be no further losses of non-structural carbohydrate, which is the sum of water soluble carbohydrate and starch added together, just through storage alone. The level of non-structural carbohydrate in any forage can be highly variable and is dependent on grass types and environmental conditions during growth and at the time of harvest. The only way to know what a forage provides and therefore how suitable it is for your horse is to get the forage tested.

Is There An Alternative To Hay Or Haylage?

If hay or haylage is in short supply what’s the alternative? A number of the Dengie fibre feeds can be used as partial or full hay replacers. Dengie’s Pure Grass brings the field to the stable, or for good do-ers Hi-Fi Lite is an excellent option. We can provide more information about Dengie’s range of forage replacers, including those suitable for veterans with poor teeth.