Don't send your profits down the drain

Drainage pipes under silage clamps aren’t all they’re cracked. up to be. In fact, according to silage expert, Dr Dave Davies, (pictured) they can do more harm than good. He explains how expelling CO2 and drawing in air can compost your forage.

Drawing in air

Introducing drainage pipes alongside walls, or anywhere in the clamp, acts not to remove liquid but to allow carbon dioxide (a silo-beneficial gas) to flow out of the clamp and air (or more specifically oxygen) into the clamp. This will occur on the first day of filling and continue until the clamp is opened. Rather than resulting in nutrients being preserved by anaerobic ensiling processes, they are instead respired, as in the composting processes.

The result is silage with a lower protein and digestible energy content, a higher ash content, and a greater risk of bacterial pathogens surviving such as clostridia and listeria, which could potentially cause abortions and in extreme situations, death. It also increases the risk of mould growth and mycotoxin production, some of which can pass through the animal into the meat and milk.

Ineffective at removing water

In addition, placing a drainage pipe along the side wall of a clamp is ineffective at removing water or effluent from the clamp. The main reason is that the flow of liquids is complex. The silage is a matrix of different lengths of chopped fibre at different dry matter contents with different compaction densities. Just like a river, the flow of liquid will take the route of least resistance. There is no way a farmer can fill the clamp to ensure that this route is to the side wall and then down that to the base. The physics of that process are just too complex.

The best way to stop effluent flow in the clamp is to not produce it in the first place by ensiling forages at greater than 28% dry matter (DM), where effluent flow is minimal or zero. Most farmers aim to do this since effluent is a loss of forage quality and quantity. Ensiling low DM forages results in extensive fermentation product formation, which also has the potential to negatively affect the animal. This knowledge is widespread in the farming community, as demonstrated by the national average dry matter of silages being around 32% for the past few years.

Obviously, some years the weather is against silage production and in these years the most effective way of ensuring effluent does not escape into water courses, whether above or below ground, is effective drainage around the peripheral region of the clamp to remove rainwater and effluent into storage tanks. Having a drainage pipe along the side wall will not aid this process one iota; it will just increase issues further down the ensiling and feedout process.

I strongly advise against placing any pipes in the silo for the benefit of animal nutrition, livestock health and welfare, and importantly for the environment.