It's all about beneficial bacteria - YHC magazine Spring 2017 issue

At a recent equine event that Devon Haylage attended we were asked numerous times exactly how we make our haylage.  It was also apparent that there are still some myths surrounding haylage and its suitability as an ideal feed for horses.  The aim of this article is to guide you through the science behind the haylage making process to illustrate what good haylage should be like and how it could benefit your horse.

Firstly, the whole process starts many months before the cutting season.  Commercially made haylage, intended for the equine market should be made from fields solely intended for this purpose and not from surplus cattle forage or hay that has been unable to dry.  Surplus cattle forage may not have been grown or produced with horses in mind and may therefore be of the wrong dry matter, fibre or energy content.  Reputable producers should also be aware of the importance of caring for the soil in a holistic manner to achieve the best possible mineral ratios and protein quality within the crop.  Several factors including the quantity and type of fertiliser applied, the pH of the soil and the amount of soil compaction will all contribute to the nutritional quality of the end product.  At Devon Haylage we believe that forage should not simply be regarded as ‘gut fill’; we strive to produce a product that is as nutritionally suited for horses as possible so that it can safely be fed as their main feed.

Once the fields have been tended appropriately for several months and the grass is nearing maturity (the development of seed heads), producers will be keeping a very close eye on the weather forecast!  At Devon Haylage we cut our Ryegrass first as this reaches maturity before the Timothy or Native grass & Herb Mix.  We will be looking for a higher stem to leaf ratio and well developed seed heads as this will produce haylage with high levels of fibre.  We will cut the grass from mid-morning onwards on a good sunny day once sugar levels have built up to make the haylage really palatable (this sugar will then be broken down by bacteria to form Volatile Fatty Acids (VFA’s)).  Drying time will be dependent on sunlight levels, the amount of breeze and the number of times the grass is turned but generally it takes around 36 hours to dry to the desired dry matter.  We aim for a dry matter of about 70%.  This is quite high compared to some haylage but this ensures that the haylage is not too acidic and it’s economical to feed as with a wet product more has to be fed for the horse to consume enough dry matter.

Haylage can then be baled into small or large bales.  It is important that the grass is tightly packed so to exclude as much of the air surrounding the grass as possible, this encourages the most efficient fermentation.  At Devon Haylage we make the haylage into large bales at harvest and then break them down using specialist equipment throughout the year.  This enables us to reject any haylage that fails to meet our high standards and the product is consistent in quality.

Once the grass has been baled and wrapped an air tight environment is created and this is where the science happens.  Firstly, any air trapped between the grass stems is used by bacteria on the surface of the grass as they respire.  This phase is undesirable as water and heat is produced.  The aerobic bacteria will also consume soluble carbohydrates which would otherwise be available for the beneficial lactic acid bacteria (explained later) or the animal consuming the forage.  If there is any breech in the plastic bale covering then oxygen entering will continue to feed this undesirable process. 

The next phase involves the growth of acetic acid producing bacteria in which the haylage begins its anaerobic fermentation.  This is an important phase as the acid produced acts to lower the pH necessary to set up the subsequent fermentation phases.    This drop in pH acts to inhibit the growth of acetic bacteria and they decline in numbers.  Lactic acid producing bacteria then take over which ferment soluble carbohydrates.  This is why haylage is low in sugar, as these acetic and lactic acid producing bacteria are responsible for breaking down carbohydrate (sugar) during their replication to form VFA’s (acetic and lactic acid).  This is what gives haylage its wonderful smell!  Hay doesn’t go through this process and so may not be suitable for laminitics if the sugar content is high.

This phase is the longest phase in the process because it continues until the pH of the forage is sufficiently low enough to inhibit the growth of all bacteria. When this pH is reached, the forage is in a preserved state and it is safe to feed. No further destructive processes will occur as long as oxygen is kept from the haylage.  If air is allowed to enter through a hole then rapid spoiling will occur. When grass is baled and wrapped with a very low dry matter of say around 30%, the fermentation can be affected.  Instead of lactic acid producing bacteria developing, large populations of clostridia bacteria may grow which produce butyric acid instead which results in a sour tasting product.

Some people are concerned about botulism when feeding haylage.  Botulism is caused by toxins produced by Clostridium botulinum bacteria however there needs to be significant soil contamination along with a low dry matter (wet) haylage for the botulism bacteria to develop.  Part of our in depth nutritional testing looks at the Soil Contamination Index, which has always given a low reading, providing our customers with added security.

Haylage was first developed as an alternative to hay for being dust free and this still remains its biggest selling point.  Mould and fungus’ can simply not grow in an anaerobic environment whereas even if hay smells OK, there will always be some degree of mould and fungal spores present.   Once haylage has been opened however and exposed to the air mould and fungus will then overtime begin to grow as aerobic processes begin to degrade the organic matter.  Wet haylage will be susceptible to this faster than a dryer haylage which is why dry matter is so important to us.  Our haylage will remain safe to feed for at least 7 days after opening and when fed at the appropriate levels could provide the majority of the energy and protein that your horse requires without the need to feed large quantities of additional hard feed.  We simply advise customers to balance the forage using a bespoke or broad spectrum balancer.  Whichever forage you choose to feed just make sure it is appropriate for your horse by looking at the nutritional analysis for that year’s crop and sourcing it from a supplier who cares as much about your horses forage as you do!