Hay, Haylage and Treated Hay for Horses
Table of Contents
Untimely rains during the haying season result in anxious farmers and calls regarding methods of preserving hay as an alternative to dry hay. Under normal conditions, hay is cut, crimped, raked and/or turned to reduce drying time, and then baled. The moisture content of standing hay varies from 65-85%. Hay destined for small square bales needs to be dried below 15% (85% dry matter) before baling for horses, to reduce the chance of dust. The majority of hay is air dried in the field over a 3 to 5-day period. Some producers build hay dryers to enable them to bale hay at moisture contents up to 30%. These dryers mechanically draw dry and often heated air through the bales reducing their moisture level. Square bales will normally lose moisture during storage, resulting in a final dry matter content of about 89% or 11% moisture.
If the hay is destined for baling into round bales, the hay should be field dried to 13% moisture prior to baling. Round bales, baled at 15% moisture level (85% dry matter) or greater, do not lose moisture in the storage period as easily as the smaller square bales and often become dusty. Therefore, hay being baled into a round bale form must be drier before baling.
Dust in hay comes from four sources:
During a wet haying season, producers often look for alternative forms of forage than the traditional dry hay. Horse owners can consider the use of haylage (bagged or wrapped) and/or preservative-treated hay. These alternatives will allow producers to bale during unpredictable weather conditions and thereby ensure higher feeding values rather than waiting for suitable drying weather before cutting or having hay rained upon.
Haylage, grass silage, or baleage are terms given to hay that has been ensiled. Ensiling is a preservation method requiring;
At pH 5 and below, bacteria and fungi will not grow and the material is maintained in a stable state unless air enters the bag/container.
In the case of round-bale silage (baleage), the hay is baled at about 45-50% moisture and immediately wrapped with plastic, or placed in a bag. The wrapping will prevent further entry of oxygen while the young plants respire using up the remaining oxygen. The pH will drop below pH 5 within a few days. Should the bag become punctured, the haylage will undergo secondary fermentation and spoilage will occur in those areas where oxygen is present. If the forage is baled too dry (25-30% dry matter), incomplete fermentation and higher pH levels occur, and there is a greater chance of growth of undesirable bacteria and fungi. Growth of Clostridia botulinum and production of deadly toxins (botulism) can be the result.
Treated hay is the name used when a commercially available preservative product is applied to hay. These products are often used on hays between 15-30% moisture and are sprayed on the hay during the baling process. There are two main types of preservatives; those containing an acid, such as propionic, acetic and formic acids, and those containing mold inhibitors.
The acids being used today are buffered and are less likely to cause corrosion of equipment than previous products. Propionic and acetic acid are commonly combined. They are produced naturally in the cecum and colon of horses as a result of microbial digestion of fibrous feed (1). These organic acids are potent mold inhibitors. The acids are applied to the hay during baling when it is difficult to dry the hay below 15% moisture content. Studies have shown that heating and molding of hay during storage is decreased with the use of these preservatives (2). However, these products must be applied evenly onto the hay to be effective. Studies have also shown that, when given the choice of dry hay or preservative-treated hay, horses preferred the dry hay. However, when only given treated hay, daily consumption did not decrease (1,2,3). The preservatives, when used properly, allow the storage of hay at a moisture content level of up to 30% (2). Treated hay should not be placed beside dry hay or the dry will absorb moisture from the treated hay and mold.
Mold inhibitors are routinely applied to hay in a similar manner as the propionic/acetic-acid products. They are commonly used in hay fed to cattle but no research for horses has been found to compare parameters, such as acceptability, daily consumption and weight gain. Antidotal reports suggest that horses readily consumed hay treated with these products.
Since large wrapped round-bale haylage came into common use, there are several reports each year of groups of horses dying of botulism after eating this type of feed. Commonly, the haylage does not look or smell spoiled, but horses eating it develop botulism.
Antidotal findings suggest that haylage baled, bagged, or wrapped drier than the normal 40-50% moisture level are more prone to containing botulism toxin. An increased risk of botulism occurs when:
Producers should use a hay preservative on hay in the 15-30% moisture range rather than attempt to make haylage by bagging or wrapping the bales.
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