Haylage, is simple grass that has been sealed to exclude any oxygen from getting to it. Grass naturally has a range of bacteria in it, and some of these bacteria are known as lactobacilli, or bacteria that produce lactic acid. They do this by converting the soluble carbohydrates (such as starch and sugar) into lactic acid. This is a process otherwise known as anaerobic respiration. The lactic acid will preserve (or pickle) the haylage, and break down the proteins into a more digestible form for the horse. This results in a product that can be stored for a long time, is free of dusts and spores, and can provide lots of digestible energy to the horse.


So what are the conditions required for making good haylage?

– As must oxygen as possible must be removed from the product

The haylage sholud be tightly compressed to expel as much oxygen as possible. This is achieved by having the baling machine set to produce a highly compressed bale with very tight strings.

If there is too much oxygen in the bale, the aerobic bacteria that promote spoilage will work faster than the anaerobic bacteria that produce lactic acid that preserves the grass. There is always an element of aerobic respiration on a newly sealed bale, but it should only last for a very short time whilst any remaining oxygen is used up before the aerobic bacteria take over.

– The right moisture content

The moisture content is very important for the fermentation process to work correctly. To much moisture will result in a slimey silage like product that is no good for horses. Conversely, too little moisture will prevent the fermentation process from working properly, resulting in an unpalatable ‘musty’ bale that is also no good for horses.

We aim for a moisture content of around 65% dry matter, which we find provides sufficient moisture for the aerobic bacteria  to work, but does not make the bale unnecessarily wet and heavy. If the grass has been cut at a later than idea stage, the moisture content needs to be towards the higher end, as the grass will be more lignified and stalky.

– An adequate supply of fermentable carbohydrate

Soluble carbohydrates from starch and sugars are required by lactic acid bacteria to produce lactic acid. Sugars and starch are generally higher in younger, less mature grasses, and lower in older, stemmy grass.

This is why old ‘meadow grass’ does not make into good haylage. There is not sufficient sugar for fermentation to take place, so you end up with an unpalatable brown coloured product, rather than a sweet smelling golden coloured product.

– Sufficient lactic acid producing bacteria 

All grass has natural bacteria in it. Older, mature meadow grass will have less suitable bacteria, and may also contain too many of the wrong type of bacteria that will promote spoilage and moulding. Young ryegrass will naturally have plenty of lactobacilli if it is cut at the correct growth stage. Grass that has been cut too late, or product that needs to be sold sooner than is ideal, may have an additive applied that will increase the amount of lactic acid bacteria present, speeding up fermentation.

– A clean stand of grass

The ideal grass for horse haylage will be a tall, fast growing, stemmy species that grows straight up and into head in early June. It is important to ensure that there is no dead, overwintered growth lying underneath the new stand of grass. This will show up as dark brown dead material in the finished product and will be unpalatable and horses will tend to separate and drop it.

The grass should also be free of weeds such as docks and chickweed that will not ferment properly. Of course, there should be absolutely no injurious weeds such as ragwort.

– The right protein level 

As grass gets older, the level of nitrates will drop as they are used up by the plant. The amount of nitrogen in the grass plant is proportional to the amount of protein (or digestible energy) available to the horse. This is why it is so crucial to time the cutting of the grass correctly. The protein level can be monitored throughout the growing season by sending samples off to a laboratory.

For a horse, the protein level should always be below 12%, with 10-12% being preferred for horses in hard work, and 8-10% for good doers and horses in lighter work.


If you are looking for a supplier of good quality haylage, delivered to your yard and with every bale guaranteed, why not give Swanmoor Haylage a call for a friendly chat and to request a sample?