Blog: Healthier Silage

By Dr Mike Wilkinson, Independent Silage Consultant

Twenty-five years ago, Simon Wigley (Passion Ag’s founder) and I carried out a small trial of a new co-extruded plastic film which contained an oxygen-barrier component. We found that loss of dry matter from silage during the storage period was halved when covered with the co-extruded film, and there was no visible mould development, compared to the same crop stored under conventional polyethylene film. Many trials subsequently confirmed our initial results. Recent improvements in silage film technology have resulted in a range of multi-layer products for different farm conditions.

Research has shown that silage covered with an oxygen-barrier film is superior hygienically to that covered with conventional plastic.

Understanding the Problem

Well-made silage is a relatively safe feed for livestock, but things can go wrong. Animals (and humans) can become sick. Milk and cheese may be contaminated and rendered unfit for human consumption.

The health status of silage, and that of livestock that eat it, reflects the microbial and chemical composition of the crop at harvest, the fermentation in the silo or bale, and the extent to which the silage is resistant to aerobic spoilage (composting) during storage and feed-out.

Risk factors to health include:

• Infection and contamination of the crop.
• Poor crop consolidation.
• Inadequate acidification post-ensiling.
• Oxygen ingress into silage during storage and feed-out.

These risks are increased by:

1. Extreme weather before and during silage making. Low crop dry matter at harvest makes rapid acidification less likely and increases the risk of secondary fermentation when lactic acid is converted to acetic and butyric acids, with loss of palatability and nutritional value. High temperatures at harvest can inhibit growth of desirable bacteria. Physical damage to crops and silage covers by gales, hailstorms and wildlife can cause infection by yeasts and moulds with production of mycotoxins.
2. Slurry and soil contamination. Inoculation of the crop with faecal organisms shortly before harvest increases risk of poor-quality fermentation, reduced silage feed value, and can result in contamination of milk and cheese.
3. Secondary fermentation. Butyric acid bacteria can develop during the storage period in wet, poorly acidified silage. Their spores can contaminate milk and hard cheese made from the milk can “blow” during storage, with serious loss of value.
4. Pathogenic microorganisms in crop and silage. Potential pathogens can include Shiga-toxin producing E. coli (STEC), Mycobacterium bovis, Listeria monocytogenes, Clostridium botulinum, Bacillus cereus and Cryptosporidium parvum. Signs of infection in livestock can be traced back to contaminated silage.
5. Toxins from moulds in silage. Mycotoxins can be responsible for depressed appetite and reduced immune status of livestock, and contaminated milk and cheese. Contamination of silage by Penicillium moulds may result in milk being rejected for human consumption by the dairy.
6. Toxic gases can be produced in the silo soon after harvest. Yellow/reddish-brown fumes of nitrogen oxide gases are potentially toxic to livestock and humans because the gases combine with water in air to form nitrous and nitric acids which can destroy lung tissue and cause respiratory distress.

Practical Solutions

The introduction of oxygen-barrier film covers for silage was a game-changer in crop conservation. But superior covers cannot prevent health risks if the crop itself is not relatively clean at harvest and if silo management is sub-standard.

Practical tips for making and feeding healthier silage:

1. Start with a clean crop. Avoid applying high levels of fertiliser nitrogen, slurry or farmyard manure to grass crops shortly before harvest. Do not cut too close to ground level.
2. Harvest as early as possible in the season, especially if the crop has been exposed to a period of hot weather that has accelerated maturation and dry-down.
3. Wilt crops in dry weather. Take heed of weather forecasts. Pause if the weather deteriorates. Avoid repeated crop tedding and turning of grass and legume crops to reduce risk of soil contamination. Try to avoid over-wilting.
4. Chop drier crops short to allow good consolidation in the silo and exclusion of as much air as possible during filling.
5. Apply an effective additive. Aim to minimise risk of poor-quality fermentation and aerobic spoilage by investing in a scientifically proven additive.
6. Consolidate the crop in thin, uniform layers during filling to achieve high-density silage throughout the silo.
7. Cover immediately after harvest with a proven, high-quality oxygen-barrier film to produce a well-preserved product throughout storage and feed-out.
8. Pay attention to detail, ensuring that peripheral areas of the silo are well-rolled and completely covered. Tape over any holes. Try to avoid over-filling the silo.
9. Look out for toxic gases. If you see signs of yellow or reddish gas fumes escaping from the silo after harvest, stay well clear and remove all livestock from the vicinity.

Silage is valuable stuff. Protect your investment by adopting these practical measures so that you produce higher-quality silage, healthier livestock, and improved milk hygiene.

For expert advice and innovative silage management solutions, contact the Passion Ag team — we’re here to help you maximise your forage investment.