Why does grass silage need inoculant?  

October 22, 2020

Why does grass silage need inoculant?  

Last season was a challenging season for many, with very wet conditions in some areas and extremely dry conditions in others. Grass silage demand soared, and in most cases there was not enough feed to go around. Now that we have an opportunity to replenish our supply of grass silage, it is a good time to consider inoculating grass with the Nutritech range of Sil-All® inoculants to minimise silage losses, improve silage quality and have more stable silage in storage.

Applying inoculant to grass silage is more important than you might think, as grass can be very challenging to ensile and nutrients can easily be lost. Grass silage can be difficult to ferment for several reasons:

  1. High water content (low dry matter). Water has a relatively neutral pH (pH7), meaning grass silage requires a lot of acid to bring the pH down below the critical level of pH 5. One of the strongest acids is lactic acid, so applying an inoculant with a powerful group of efficient and specific lactic acid bacteria is the best way to minimise silage losses and spoilage.
  2. High protein levels. Protein has a buffering effect, meaning it is more difficult for the pH to reduce. Nitrogen boosted pastures, or pastures with high clover content will have higher protein content and will be more difficult to ensile. Furthermore, these proteins can be broken down by proteolytic clostridia bacteria, resulting in high ammonia N and an increase in putrid compounds, all of which significantly affect silage palatability.
  3. High calcium content. Much like lime when applied to soil, high calcium in silage can keep the pH high. Legumes such as clover and lucerne can be particularly high in calcium, making these crops much more difficult to ensile.
  4. Risk of soil contamination. Grass silage can be a high risk for soil contamination due to soil splash on the plant, low mower height, harvesting in wetter conditions, and mud sticking to tyres of packing machinery. Soil contamination increases the presence of clostridia spoilage organisms, which can increase the risk of spoiled silage, especially if the silage pH has not quickly reached pH 5 or less.

Many grass inoculants have only 100,000 colony forming units (CFU), while some have no bacteria at all. Using a lower specification inoculant is not necessarily going to save you money as the risk of spoilage will be greater. The Nutritech range of Sil-All® inoculants apply high numbers of well tested, silage specific lactic acid bacteria that help overcome the challenges of ensiling grass silage.  These inoculants have been proven to produce higher quality silage with less silage losses, even in low dry matter grass and lucerne crops. In addition to specifically selected bacteria, Sil-All® inoculants contain enzymes which on their own improve the quality of silage by increasing digestibility and ‘opening up’ plant tissues to makes the inoculant more effective, as the bacteria can better access the nutrients they need to rapidly ferment the silage.

Now is the time to do everything you can to make good grass silage that will store well, be palatable to livestock and have retained as many nutrients from the fresh crop as possible. Grass silage can be difficult to ferment, so contact the team at Nutritech to see how the Sil-All® range of inoculants can help.

This article was originally published in the NZ Rural Contractor & Large Scale Farmer magazine in October 2020.

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