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Making hay while the sun shines

July 26, 2021

Conserving forage in the summer months for horses to eat in winter is necessary for almost all horse owners in UK and Ireland due to climate, growing conditions, management and turnout options throughout the year. There are number of different types of conserved forage which are commonly fed to horses and each are grown, processed and stored in different ways. It is important to remember that any conserved forage will have a lower nutritional value than fresh grass. A laboratory analysis will be necessary to ascertain both the hygienic (mould and bacteria levels) and nutritional quality. The stage of growth at harvest is a key factor influencing nutritional content. As the plant matures the fibre fraction increases and Crude Protein decreases, leading to a decline in digestibility and overall energy availability, (Virkajärvi et al., 2012). Hay and haylage analysis is offered by a number of feed companies as well as The Irish Equine Centre.

The main types of conserved forage which are fed to horses in Northern Ireland are hay and haylage. Ideally horse owners should produce or purchase enough of the same batch of good quality forage for the whole season. Obtaining haylage with consistent nutritional values can be difficult. This is mainly due to the variation in moisture content. Hay that is well made and stored well tends to be much more consistent and therefore better for overall horse health, (Creighton, 2020). Changing batches of forage throughout the season can disrupt the horse’s digestive tract and if it is necessary to do so, this should be a gradual process. Weather conditions, storage and species of plants account for the wide variation in forage quality.


The more traditional of conserved forages for horses, quality hay will be between 80% – 90% Dry Matter (DM). Hay is extremely weather dependent when cutting, needing a number of rain free, warm, sunny days to turn, dry and wilt the cut grass before baling. This drying process preserves the hay to a level which discourages microbial growth. There are two main types of hay, “Seed Hay”, which is one or two specifically sown, grass species which have been sown for the purpose of making hay, and “Meadow Hay”, which is a mixture of different grasses and herbage, which make up an established permanent pasture. Unless hay has been dried to at least 90% DM, it should not be fed to horses until at least 8 weeks after it is cut. This allows the sugars and fermentation process to settle to a safe level before feeding. If hay is baled and tested with a very low moisture content, it can be fed right away, (Crandell, 2017). Caution should be used in purchasing hay that was wet when baled as too much moisture affects the quality.

Once dried and baled, hay must be stored in a dry, well ventilated area. Some studies have suggested that hay which is uncovered in storage can act like a sponge and absorb moisture from the air during damp winters.

Fungi and mycotoxins are now recognised as a major cause of respiratory conditions in horses, and in particular the pathogenic fungus Aspergillus is of concern. In a study carried out by the Irish Equine Centre in 2007, investigating mycotoxins in Canadian and Irish forage, Buckley et al., reported that fifty percent of the sixty-two Irish hays sampled contained the pathogenic fungi, Aspergillus. Haylage proved superior to Irish hay but not as good as Canadian hay with twenty of the fifty-four Irish haylage samples containing pathogenic fungi.


Haylage is made when grass is cut and turned just like hay but, instead of being allowed to dry completely on the field, it is baled when the grass has wilted and the moisture content is between 55-65% DM. This takes around 24 hours in good drying weather. The bales are then compressed to half their original size and wrapped air tight, in plastic. Natural fermentation inside the plastic prevents the development of fungal spores and preserves the grass.

Once the bags have been sealed to exclude air, naturally present bacteria and yeast start to break down the sugars – a process called fermentation – in order to preserve the grass and retain maximum nutrient levels.

Haylage has a much higher moisture content than hay which therefore means that more haylage is required to be fed as compared to hay to meet the daily recommended guidelines for dry matter intake. Haylage can contain higher crude protein, fat and digestible energy. When feeding haylage, the spoilage process can begin quickly if the bale is exposed to air; this may be due to damaged wrapping or not using the bale quick enough once opened. Fungal spores will develop, and this should be carefully assessed before feeding. It is recommended that opened bales of haylage are used inside of four days in the winter and three days in the summer, (Irish Equine Centre, 2020).

The decision to feed, produce or buy a certain type of forage will come down to many factors including management systems, storage facilities and availability and will vary between horse owners. When making or purchasing forage for horses, it is vital to obtain the highest quality possible, which will be determined by weather in these summer months as well as storage through the winter. If in any doubt, nutritional advice should be sought from an equine nutritionist or veterinarian.


  • Buckley, T., Creighton, A. & Fogarty, U. (2007) Analysis of Canadian and Irish forage, oats and commercially available equine concentrate feed for pathogenic fungi and mycotoxins. Ir Vet J 60, 231.
  • Crandell, K., (2017), Fresh-Baled Hay for Horses, EquiNews – Nutrition and Health daily, Kentucky Equine Research.
  • Creighton, A., (2020) Hay quality, sampling, testing protocols, importance of hay quality for racehorse trainers, Irish Equine Centre, European Trainer
  • Müller, Nostell, Bröjer, (2015) Microbial Counts in Forages for Horses—Effect of Storage Time and of Water Soaking Before Feeding, Journal of Equine Veterinary Science, Volume 35, Issue 7, Pages 622-627,
  • Virkajärvi P., Saarijärvi K., Rinne M., Saastamoinen M. (2012) Grass physiology and its relation to nutritive value in feeding horses. In: Saastamoinen M., Fradinho M.J., Santos A.S., Miraglia N. (eds) Forages and grazing in horse nutrition. Forages and grazing in horse nutrition, vol 132. Wageningen Academic Publishers, Wageningen.