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Making hay

Making hay

Written by Becky James BSc MSc


Hay is notoriously known for being dusty, which affects the respiratory system of both our horses and ourselves. To understand where this dust comes from, and what we can do about it, let’s take a closer look at how hay is made and the challenges this 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 15-20% of weight, 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 vapor pressures between the surrounding air and in the surface tissues of the plant. The ideal drying conditions are dry with a light wind; however, unpredictable weather means that 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, while the stems are thick so they are 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” in humans and cause a similar response in horses.

Once the moisture content has been reduced to 40% of total weight, 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 often made difficult by less than ideal weather conditions.

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 moisture content greater than 15% in weight, varying losses occur, mainly associated with microbial respiration and heating. It has been estimated that on average, during storage, hay of 15% moisture will lose 5% dry matter, and this will increase by 1% for every further 1% increase in moisture up to 20% in weight.

The varied conditions for hay making, storage and species of plants used may account for the large variability in hay quality across the country.

In the field, grass contains a range of microorganisms, and 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 molds such as Penicillium and Aspergillus.

Horses are highly sensitive to these molds, bacteria and other dust particles from hay, and inhalation of these particles results in airway inflammation (Inflammatory Airway Disease or IAD) 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 212⁰F. This method is proven to kill bacteria, mold and fungal spores and reduce all respirable dust by up to 98%, and it 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)

Haygain is a practical solution because it’s simple to do: you fill the steam generator with water, the hay chest with hay (various sizes are 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 manifold, ensuring the hay is steamed from the inside out. This, coupled with the thermally efficient hay chest, results in the hay reaching temperatures above 212⁰F 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 that veterinary hospitals use it to encourage horses to eat post-surgery, and even picky eaters give it the seal of approval.

At this time of year hay quality is at its lowest point, having been stored all winter. Both the nutritional and hygienic quality will have deteriorated over this time, which often means the hay is also less palatable. There is no better time than the present to start steaming your hay.

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