Impact of rain on Hay & Silage

December07

Impact of rain on Hay & Silage

What a tough year it has been to make hay and silage. Having only had a few short windows of good drying weather (with showers of rain, high soil moisture and morning dews, coupled with big pasture yields) average wilting and drying times have been longer than previous years. In an ideal world, whether its hay or silage, we aim to get the fodder from cutting to baling and storage as quickly as possible and without any rain, this helps to lock in quality and maintain maximum yields. So, what is the potential impact of rain?

The impact of rain largely depends on the stage of curing at the time. The dryer the fodder gets the greater the chance of damage from a rain event. The 3 main losses being: leaf shattering and loss due to additional raking, leaching of soluble carbohydrates, and prolonged microbial activity which can lead to mould and fungal growth and rotting on the underside of windrows.

Intuitively this will lead to yield losses, shattering of leaves and additional breakdown of plant material means less going into the bale, but what about quality? Research has shown that the biggest impact on quality is through the leaching of soluble carbohydrates, which means an increase in the neutral detergent fibre (NDF). This lowers the digestibility of the product and subsequently potential metabolizable energy. In basic terms, depending on the amount of rain, you end up with more stem than leaf and a lower quality product. On a side note, cereal stubble will also deteriorate in quality after summer rains due to leaching of soluble carbohydrates.

Interestingly though, studies have shown that protein is not as effected by rain events. In rain effected hays it can be common to have high fibre and protein levels but a low metabolizable energy. However, depending on the pasture species (ie clover and Lucerne) there can be some protein losses due to leaf shattering.

The impact of these losses may be confounded come feeding time, thinking that your hay and silage is better quality than it is can have significant impacts on livestock performance. It may be the difference between making joining or sale weights and not.

 

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