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Hay bale fires

As we coming into hay season an issue that we often hear about or are unlucky enough to experience is, hay fires. Many producers over the years may have not experienced a hay fire but have opened bales to find that they have heated inside. So what causes this phenomenon?

Currently many producers are under the impression that high moisture hay is the cause of hay fires; so how is it that hay baled at 10% moisture has burnt to the ground? Moisture has been the sole management tool of assessing and managing the risk of hay fires. Water itself does not lead to heating and fire but it can lead to bug growth, which are the principal cause of hay bale fires.

Baled hay naturally contains million of fungi and bacteria that produce heat as they consume the nutrients in the hay. Hay usually gets dry enough and the bugs die off or become dormant. When moisture persists then the bugs persist. Moisture measures are indicators of likely microbe action but it is not the cause.

The presence of water soluble carbohydrates or plant sugars which move from roots to stem, to flowers or seed in hay at 10% moisture can result in fire. These carbohydrates and sugars are a great source of food for microbes and hence microbe growth. Extended drying times in the windrow, in conjunction with high plant sugars allows mould, fungi and bacteria to grow, leading to a higher risk to heating and burning when the hay is baled.

So control the bugs and you control the risk of heating, even in hay that started at 20% moisture. If you are concerned or there are predisposing factors that have occurred during the hay making process there are products on the market that inhibit bug growth and reduce the risk.

Also be aware that hay that has heated or caramelised in bales may be quite palatable but nutritionally may not be below expectations. This will be a result of heat damaging the protein, a reduced dry matter, reduced energy and many of the vitamins are destroyed. The crude protein may still be okay on a feed analysis but much of it may not be available to the animal.

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