Written by Becky James BSc MSc
Hay is notoriously known for being dusty which effects the respiratory system of both our horses and us. To understand where this dust comes from, we need to take a closer look at how hay is made and the challenges the process presents.
The definitive aim of haymaking is to produce a palatable product that retains the nutrient quality of the original crop. Grasses and legumes are cut, dried and baled into hay. The intention is to reduce the moisture content to a level low enough to inhibit the action of plant and microbial enzymes. To make good baled hay the moisture content must be reduced to 150-200g/kg, and this can be difficult to do in inclement weather conditions.
Drying begins as soon as it is cut but the rate depends on the difference in water vapour pressures between the surrounding air and in the surface tissues of the plant. The ideal drying conditions are dry with a light wind, however, weather patterns mean hay is rarely made in ideal conditions!
Different parts of the plant dry at different rates, the leaves dry out more quickly because they are thin with a large surface area, whereas the stems are thick so slower to dry. This can lead to leaf shatter during mechanical handling and loss of the more nutritious leaf material. If drying is prolonged due to bad weather conditions the action of microorganisms; bacteria and fungi will cause changes. Thermophillic actinomycetes are often present in such hays and are responsible for the allergenic disease “Farmer’s Lung” and cause a similar response in the horse.
Once the moisture content has been reduced to 400g/kg, plant respiration ceases and any further nutrient losses in the field are largely due to weathering and handling of the crop during hay production, something that is not always possible in the UK climate.
Hay yield and quality are reduced if exposed to rain during drying as soluble components are leached out. Leaching has been reported to remove 20-40% of the dry matter, 20% of crude protein, 35% of non-fibrous carbohydrates, 30% of phosphorous and 65% potash (Shepherd et al 1954).
In stored hay with a moisture content greater than 150g/kg varying losses occur mainly associated with microbial respiration (and heating). It has been estimated that on average, during storage hay of 150g moisture/kg will loose 5% dry matter and this will increase by 1% for every further 10g/kg increase in moisture up to 200g/kg.
The varied conditions for hay making, storage and species of plants used may account for the large variability in quality seen in hay across the UK.
In the field grass contains a range of microorganisms, those present are likely to persist during storage even if further fungal growth is prevented by drying. If the crop is not sufficiently dry when it is cut the field fungi gradually are outgrown by storage moulds such as Penicillium and Aspergillus.
Horses are highly sensitive to these moulds, bacteria and other dust particles from hay, and inhalation of these particles results in airway inflammation (inflammatory airway disease) and Equine Asthma, also known as RAO, COPD or Heaves.
Haygain hay steamers provide a practical method of dealing with this naturally occurring dust by steaming the hay at temperatures over 100⁰C. This method is proven to kill bacteria, mould and fungal spores and reduce all respirable dust by up to 98% and has been shown to reduce the incidence of inflammatory airway disease (IAD). In a retrospective study of nearly 500 horses, feeding Haygain steamed hay actually lowered the risk of finding fungi in the airway which corresponds with the diagnosis of inflammatory airway disease. After analyzing all the forage options (dry hay, soaked hay, haylage or Haygain steamed hay) steamed hay not only had the lowest risk but was the ONLY method which significantly decreased the risk of IAD. (ACVIM June 2016 “The Prevalence of Fungi in Respiratory Samples of Horses with Inflammatory Disease” by Drs J Dauvillier and E Westergren)
It’s practical because it’s simple to do: you fill the steam generator with water, the hay chest with hay (various sizes available depending on the amount of hay needed) switch it on and leave it for an hour. Steam is pumped up into the hay through Haygain’s patented spiked manifolds ensuring the hay is steamed from the inside out. This coupled with the thermally efficient hay chest results in the hay reaching temperatures above 100⁰C which is critical to achieve the improvement in hygienic quality (how clean the hay is).
You can feed the steamed hay immediately or up to 24 hours post steaming, it smells delicious and the horses seem to think so too! In fact, it’s so palatable veterinary hospitals use it to encourage horses to eat post-surgery and even picky eaters give the seal of approval.
At this time of year hay quality is at it’s lowest point having been stored all winter - both the nutritional and hygienic quality will have deteriorated over this time. This often means the hay is less palatable too. There is no better time to start start steaming your hay.