As grass growth is seasonal, and our horses’ needs are not, we need to have a way of preserving grass to ensure a constant year-round supply. Equine Nutritionist Briony Witherow gives us a detailed insight into the differences between hay and haylage.

There are two main methods of forage conservation: controlled fermentation where the pH is reduced to a level where growth of bacteria ceases, or dehydration, where moisture content is decreased to reduce microbial activity. 

Hay is an example of forage that is conserved using dehydration – the main challenge with preserving forage in this way being that it requires a longer period of dry weather to produce, whereas haylage is an example of grass preserved using controlled fermentation (and so is silage).

As a rule, when considering the digestibility of a forage, the more mature a grass becomes, the higher the potential yield, but the lower the digestibility (as it has higher levels of lignin). While very young grass in a growing state is much more digestible, if hay or haylage were to be harvested at this point, yields would be very low. There is however a point in between these two stages where a balance can be struck between digestibility and yield. 

Preservation Method

As mentioned previously, while both are preserved grass products, they are persevered using different methods. Subsequently, hay being preserved through dehydration has a much higher dry matter (lower moisture content) at over 80%, compared to a typical haylage with a dry matter of between 40 and 60%.

There are no hard and fast rules that can be applied when it comes to predicting the suitability of a hay as compared to a haylage. It cannot be generalised that hay is of lower nutritional value in comparison to haylage, nor can it be said that haylage is always lower in WSC as compared to hay. The reason for this, is that a huge variation in end product exists, due to various environmental factors. To name a few, nutrient levels within any forage crop (hay or haylage) vary depending on growth stage (maturity), time of day cut, grass species, soil fertility and light intensity. As such, even forage crops taken from the same field can vary if cut at different times of day. Equally, maturity of the crop plays a significant role - a late cut (more mature at point of harvest) haylage can be less digestible than an early cut hay. Ultimately this is why we often depend on forage analysis for more accurate guidance.

One of the most notable differences when comparing a hay and haylage product is the dry matter content, hay having a much higher dry matter than haylage. It is this high dry matter that brings with it most of the drawbacks associated with feeding hay. The high dry matter ultimately means this forage is higher in respirable particles such as dust and spores. Traditionally this is why haylage was chosen in preference over hays when feeding performance horses, due to the perceived superior hygiene. 

The high dry matter of hay also brings one of its biggest advantages. With little moisture to dilute the nutrients it contains, hay can often be fed at reduced volumes in comparison to haylage, as so much of the added weight of haylage is simply water. 

A haylage that is 50% moisture/dry matter, essentially has diluted nutrients, meaning that you would need to feed 1.5 times the weight of this haylage as compared to most hays. This may be in contrast to what many believe about haylage – the common perception being that haylage is ‘richer’ than hay and therefore needs to be fed in smaller quantities. While haylage certainly can be richer or more digestible than hay (being cut at a less mature stage), these nutrients are diluted. As such, in order to meet minimum fibre requirements, often more kilograms of haylage need to be fed as compared to hay.

The higher moisture content of haylage may lead most to assume that this forage product therefore contains no respirable particles, but this is untrue. While at a lower level than hay, haylages do contain respirable particles (bacteria and mould), so they aren’t automatically more hygienic than hay. Just like hay, haylage can be steamed to improve hygienic quality.

With the lack of a sufficient weather window for production, hay is becoming a less attractive crop. This coupled with the comparative ease of making haylage may make getting hold of good quality hay in the future a challenge. There are now many specialist horse forage producers making hay and haylage solely for equine use – these producers often have a better understanding of what it is that we require for our horses and therefore may produce more suitable, consistent products.

The invention of steamers has afforded more flexibility in our feeding of hay in particular. With sometimes questionable quality, steaming allows these forages to be fed with much improved hygiene, where in some cases they may have been unsuitable to feed. The introduction of steaming could not have come at a better time considering the challenges we face with hay production.

Making the Decision

Choice of forage should not only be based on which type of forage may be most suitable, but also what forage you can reliably source of good consistent quality.

As forage should comprise the majority of any horse’s diet, knowing a little more about where we are sourcing our forage from and what questions to ask from the provider is key in ensuring we make the best feeding decisions.

Lastly, once you’ve made your decision, always remember to properly transition you horse from one forage to another –even if it is just a different batch of hay or haylage. Changes in forage are reported to result in a greater risk of colic than changes in concentrate feed.

DM – Dry Matter

WSC – Water Soluble Carbohydrate