Animal health
tinues after chopping, this can help towards the removal of ox- ygen in the pit. This process con- verts 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.
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Four factors to ensure high quality silage
EXPERT VIEW
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
age. Some of these – such as the weather – are outside our con- trol. But good management can help ensure producers make the healthiest silage possible.
M 1. Fresh grass
Silage quality is determined mainly by the quality of the crop being ensiled. Leafy, young, im- mature crops tend to be lower in fi bre and high in protein and sug- ars. Protein degrades and fi bre levels increase as grass matures. Older crops produce silage with more bulk but are general-
any factors infl u- ence whether silage is good or merely aver-
ly poorer in quality and have low- er 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 diffi cult 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 splash- ing onto the crop and pick up at harvesting. Wet silage also pro- motes 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 ef- fort should be made to ensure that the grass is pitted correctly to al- low for optimum fermentation.
The pit should be fi lled 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 low- er bunker densities have been proven to have greater dry mat- ter losses compared to higher den- sity 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 num- ber of wraps needed is usually determined by the dry matter of the grass, 6-8 layers of fi lm is the minimum recommended amount.
3. Fermentation
The goal for optimum fermenta- tion 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 produc- tion causing heating, dry matter loss and the production of less de- sirable acetic acid.
Respiration in the grass con-
The goal for optimum fermentation is to remove oxygen from the silage as soon as possible
They can help accelerate fer- mentation rates by rapidly drop- ping 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” fer- mentation.
The preferred option is to use Lactic acid bacteria (LAB) such as Lactobacillus plantarum, L. ac- idophilus, Pediococcus pentosa- ceus and Enterococcus faecium, these bacteria produce only lac- tic 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 re-
moving a least 6 inches from the feed face a day, keeping the face smooth and limiting the face ex- posure. Managing the pit face will help stop the introduction of ox- ygen into the fermented silage and potentially starting second- ary 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 profi tability. Grace Thomas is a nutrition-
ist for animal nutrition company Agriking. For details, visit www.
agriking.com.
AUGUST 2018 • ANGLIA FARMER 53
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