Losses in quality and quantity occur during silage making. Of every 1000 kg grass dry matter in a silage sward, between 150 over 300 kg does not make it into the animal’s mouth as silage. Furthermore, the digestibility of the ingested silage can be up to 7% units below the digestibility of the silage sward. These losses occur in the field through leaf shatter, respiration, leaching by rain, incomplete pickup and soil contamination, at the silo during filling, through effluent, poor fermentation etc. and during feeding through respiration and spillage etc. The actual loss rate will vary depending on the crop involved, the silage making system, the standard of management and the weather conditions.
Some of these losses are unavoidable but others can be greatly reduced or prevented. For example, a sward yielding 6000 kg grass DM/ha produces 5040, 4620 and 4200 kg edible silage DM/ha where quantitative losses of 16% (excellent management), 23% (good management) and 30% (poor management) occur. Corresponding quality losses could be 0, 1.5 and 4% units digestibility. The digestibility loss difference of 0 vs. 4% units digestibility requires over 1 kg concentrate/animal daily to undo. These values demonstrate the importance of management practices that reduce losses during silage production and feedout. They include efficient mowing, conditioning and pick-up, effective wilting during good drying weather, fast filling and perfect sealing of the silo, ensuring good fermentation and relatively little effluent, fast and tidy feed-out, and sensible feed provision and waste removal at the feed trough.
Harvest losses are increased with double cutting by the mower blades, shatter of grass particles following impact by the mower blades or tines. Losses are increased as short particles of grass are dropped onto the ground, which are missed by the harvester. Uneven mowing due to uneven ground or lodged grass will lead to the harvester leaving grass behind.
Losses also occur through respiration while the grass lies on the ground especially during warm, humid conditions with poor drying. Leaching losses occur during periods of heavy rainfall. This is a bigger problem where the mown grass had been partially wilted before the rain. Leaf shatter can occur during tedding or windrowing and can also lead to short particles being dropped onto the ground. Incomplete pickup can also lead to losses. Harvested grass can be lost as it is blown from the harvester to the trailer. Physical losses of grass may occur around the silo during unloading and filling of the silo.
Heating losses can occur during slow filling and/or covering. Effluent losses can occur particularly where silage is made during wet weather or where no wilting occurs. Imperfect sealing can lead to mould growth or rotting during storage.
Limiting losses depends on restricting each of the loss components outlined above. It starts with having a healthy crop of clean grass to harvest and also having machines in proper operating order. Be prepared; remove any old, mouldy or rotting silage and clean the pit thoroughly. Ensure the walls are airtight – use a side sheet as it is almost impossible to obtain a good seal from oxygen without one. Check there is adequate effluent drainage at floor level.
Fill rapidly and spread silage evenly to consolidate well. Pressure exerted under the wheels of a heavy tractor will only be effective down to 20cm depth. If work continues the next day, sheet down overnight but do not roll the following morning as this creates a vacuum and pulls more air into the silage. Do not over fill a clamp, compaction above the walls is at least 10% lower than if the silage is level with the walls.
Seal the clamp as soon as consolidation is complete with two sheets of plastic. Use a thinner oxygen barrier sheet first and a thicker protective sheet above it. Alternatively use a new sheet covered by last year’s old sheet. Place tyres or bales on top and ensure all tyres touch each other. Use netting to protect from birds to ensure the sheet is not punctured. Make sure that unroofed clamps shed rainwater evenly and freely and that rain does not seep into the clamp Efficient mowing, conditioning and pick up, effective wilting during good dry weather, fast filling and perfect sealing of the silo, ensuring good fermentation takes place and relatively little effluent are vital components in lowering losses. A lack of attention to detail can allow losses to exceed 30% of what was available in the standing crop. Careful planning and management will reduce losses leading to a larger quantity of silage available to feed, improve feeding value and lower the costs of producing it.