Silage represents a significant investment. By harvest time considerable resources have been spent on crop production, harvesting, and ensiling. Protecting this investment by reducing losses during storage and feed-out is crucial.
Minimising spoilage preserves nutritional value and reduce hazards to livestock health, ultimately safeguarding farm profitability.
Oxidative losses from silage during storage and feed-out can lead to a significant reduction in feed value, resulting in silage that is spoiled, less palatable and which may be rejected as being inedible.
Typically, around 25% of silage stored in a 1000-tonne bunker silo may be lost due to low crop density and oxygen ingress. This lost feed must be replaced by additional silage or expensive purchased concentrates, increasing farm costs.
Spoilage losses can be especially serious from vulnerable silos such as:
1. Wide, self-feed silos: With wide feed faces and shallow fill depths (around 1.5 metres), these silos have a relatively high proportion of the total silage mass close to outer surfaces.
2. Over-filled bunkers: Silage piled above the walls and poorly compacted at the edges is at high risk of spoilage due to low density.
3. Earth-walled bunkers: Uneven surfaces and sharp stones can puncture holes in side covers which allows oxygen to penetrate the silage mass.
4. Cheese-wedge clamps: Without side walls, crops are often inadequately consolidated at the edges, increasing risk of spoilage.
5. Mushroom-shaped drive-over piles: A substantial proportion of the silage mass lies close to the large surface area of the outer edge, leaving it vulnerable to peripheral losses.
6. Smooth-bottomed bunkers: Poor frictional resistance can lead to forward slippage of the front feed face during feed-out, especially when the silo has been filled rapidly without adequate consolidation of the crop mass in the central region. Slippage can cause rupture of film covers, leading to oxygen penetration and inedible silage.
7. Delayed covering: Allowing harvested crops to remain uncovered at harvest time encourages excessive plant respiration and heating, increasing oxidative spoilage.
Implementing these best practices will help significantly to reduce silage losses:
1. Preparation before harvest: Clean out bunkers thoroughly, then line walls with high quality oxygen barrier (OB) wall film. Ensure the OB film has a proven oxygen transmission rate of less than 2 cm3/m2/24h when tested in an atmosphere of 100% oxygen (ASTM D3985-02 standard), overlapping at least 1 metre onto the top surface.
2. Improve floor friction: In smooth-bottomed silos and clamps, place a layer of straw on the floor to increase resistance and reduce risk of slippage during storage and feed-out.
3. Shape the silage pile: Create a convex-shaped top surface to encourage drainage of rainwater and reduce risk of water ingress.
4. Interim protection during harvest interruptions: if harvesting is paused due to adverse weather or mechanical issues, cover partially-filled silos promptly to avoid unnecessary oxidation.
5. Regular inspection: Side wall covers are prone to damage during filling and packing. Check and repair any mechanical damage or punctures in the film.
6. Cover promptly after filling: Immediately cover silage with OB film once filling is completed, minimising exposure of silage to oxygen and preserving nutritional value.
7. Additional protective layers: Apply a reusable cover over the OB film to prevent damage from rays of ultra-violet light, wind, birds, and wildlife. Secure the top cover firmly with gravel bags.
By adopting these practical measures, you can significantly cut spoilage losses, ensuring high-quality silage, healthier livestock, and improved farm efficiency and profitability.
JOHN MICHAEL WILKINSON BSc, PhD, RAnimSci
An agriculture graduate from Leeds and Newcastle universities, Mike Wilkinson spent over 10 years at the Grassland Research Institute, Hurley, before moving to MAFF’s Chief Scientists’ Group, then into private research and consultancy work, then into full-time university work and research management. His university work has been at Reading, London, De Montfort, Leeds, Cambridge and Nottingham. Mike is now working part-time as a consultant to the livestock industry.
Author of over 400 scientific and technical publications, Dr Wilkinson’s career has focused on improving efficiency of use of grassland and forage crops for milk and meat production with special emphasis on preserving silage with low loss of nutritional value and reduced environmental impact.