Thursday, December 13, 2018

Four factors to ensure high quality silage

July 31, 2018 by  
Filed under Livestock

The aim when making silage is to capture as much of the nutrients as possible from the fresh crop and preserve them with minimal losses, says Grace Thomas.

Many factors influence whether silage is good or merely average. Some of these – such as the weather – are outside our control. But good management can help ensure producers make the healthiest silage possible.

1. Fresh grass

Silage quality is determined mainly by the quality of the crop being ensiled. Leafy, young, immature crops tend to be lower in fibre and high in protein and sugars. Protein degrades and fibre levels increase as grass matures.

Older crops produce silage with more bulk but are generally poorer in quality and have lower feed value compared to young crop silage. Harvesting should thus take place, when possible, at peak crop quality rather than by the calendar date.

This can be difficult in wet conditions: wider swards spread within the hour will help speed up wilting. But silage harvested in wet conditions is more likely to have clostridia due to dirt splashing onto the crop and pick up at harvesting. Wet silage also promotes clostridia growth.

Target dry matter (DM) at harvesting for pit silage is 23- 30% and 30-35% for bale silage.

The nitrate and sugar level of grass before cutting needs to be considered before cutting. Sugar levels in grass silage tend to be highest after sunny weather and at peak levels in the afternoon so, if possible, grass should be mowed in the afternoon.

2. Pitting and baling

Once the crop is mowed every effort should be made to ensure that the grass is pitted correctly to allow for optimum fermentation. The pit should be filled rapidly and evenly. It needs to be packed tightly to create as dense a silage as possible.

Pits with lower densities tend to contain more oxygen which can lead to higher heat damage and poor fermentation. Pits with lower bunker densities have been proven to have greater dry matter losses compared to higher density pits.

The pit should be covered and sealed as soon as possible. Baled silages need to be wrapped with in 2-3 hours of baling. The number of wraps needed is usually determined by the dry matter of the grass, 6-8 layers of film is the minimum recommended amount.

3. Fermentation

The goal for optimum fermentation is to remove oxygen from the silage as soon as possible. Oxygen in the pit allows fermentation to occur but oxygen trapped in the silage delays lactic acid production causing heating, dry matter loss and the production of less desirable acetic acid.

Respiration in the grass continues after chopping, this can help towards the removal of oxygen in the pit. This process converts the available oxygen to carbon dioxide, water and heat whilst utilising the sugar in the silage.

The goal is to allow lactic acid producing bacteria to dominate the silage quickly and to hinder undesirable fermentations from any yeast, moulds, clostridia or bacilli. The use of inoculants on silage helps improve the quality and digestibility.

They can help accelerate fermentation rates by rapidly dropping the pH. This drop in pH helps kill off the “bad” microbes faster. Some fermentation aids such as Lactobacillus buchneri only start to grow after initial fermentation of 60 days – risking a “rogue” fermentation.

The preferred option is to use Lactic acid bacteria (LAB) such as Lactobacillus plantarum, L. acidophilus, Pediococcus pentosaceus and Enterococcus faecium, these bacteria produce only lactic acid with the least amount of shrink, DM loss and heating.

4. Feeding

Fermentation is complete when the low pH in the pit stops the bacterial action. Once the pit is stable it is safe to feed. When the pit is open, maintaining good pit face management is the best way to ensure that the open pit stays stable.

This can be achieved by removing a least 6 inches from the feed face a day, keeping the face smooth and limiting the face exposure. Managing the pit face will help stop the introduction of oxygen into the fermented silage and potentially starting secondary aerobic fermentation.

Some losses are inevitable. But the aim is to lower losses and produce the best silage possible. A good forage treatment product can help the rumen unlock more of the nutrients from forage and to improve profitability.

Grace Thomas is a nutritionist for animal nutrition company Agriking. For details, visit www.agriking.com.

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