17/11/2020
WHEN IS NEWLY-MADE HAY & HAYLAGE SAFE TO FEED?
It is traditional to allow newly-made hay and haylage to ‘cure’ before they are fed. What is this curing process and is it really necessary?
HAY Grass is preserved by drying in the haymaking process. The water content is reduced from 70-80% to ideally less 18% (or even lower if large bales are to be made). If made in perfect conditions – a sustained period of warm, dry and preferably slightly windy weather, with frequent turning before baling – any chemical breakdown after baling will cease and no heating will occur. This hay can be, and often is, fed straight away. But in the U.K temperate climate adequate drying may be hard to achieve. There may be pressure to bale slightly early for all sorts of reasons, for example, if rain is threatened, or the crop has been rained on and there is no time to fully dry it afterwards, or a heavy dew has not been left to evaporate or there is a problem with the availability of labour or machinery when it is most needed.
Hay baled with excess moisture will ‘heat’ to a greater or lesser extent. This process not only reduces the nutritional value of the crop but also results in the growth of heat-loving fungi (thermophilic actinomycetes). These fungi produce microscopic (and often invisible) spores that are inhaled by the horse during feeding, causing damage to the respiratory system. This hay may not look mouldy but to the trained ‘nose’ will never smell as good as perfect hay.
The heating process is normally complete by 8 weeks and we, therefore, recommend that unless one has intimate knowledge of the conditions under which it is made, newly made hay should be left for a minimum of 8 and ideally 12 weeks. Remember that when first baled, hay often looks and smells lovely irrespective of its moisture content. It may look and smell a lot different after 12 weeks of storage. For this reason, buying hay that has just been made 'off the field' might not always be advisable as the final state of the crop is unknown.
HAYLAGE In contrast to hay, haylage is baled slightly damp. The moisture content of the grass is reduced by a brief period of drying to from 70-80% to around 40-50%, and the bales are tightly wrapped in plastic to exclude air. Bacteria, naturally present in the grass, break down the soluble grass sugars in an oxygen-free environment. Lactic acid is produced lowering the pH of the crop and preserving the grass. As long as the wrapping remains intact, the crop can be usable for several years although gradual ingress of oxygen through the wrapping causes a slow reduction in nutritional value.
The time taken for the fermentation to be completed is variable and will depend on the moisture content at baling, the type of grass, the season of the year, the length time the crop is allowed to wilt after cutting, whether a bacterial inoculant is added during baling and other factors. While in some cases the haylage may be ready to be fed at one month it is safer to wait for two months or more. If opened during warm weather secondary fermentation and heating may occur so it is essential the bale is consumed quickly, or alternatively, all of the wrapping should be removed and the bale scattered on the floor of an empty stable.
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PENBODE EQUINE VETS, TAVISTOCK & HOLSWORTHY, DEVON
