The lowdown on good silage

DAIRY 101 SILAGE

The good stuff – a silage stack opened for winter feeding.

Story and photos by: Karen Trebilcock

So it’s spring (almost) and the grass is growing and one morning soon you’ll wake up and there will be so much grass on the farm the cows won’t be able to eat it all.

It’s time to make silage.

The energy (metabolisable energy - ME) in the grass will be high so if you have dry paddocks which the machinery won’t destroy and a genuine surplus then go for it.

Any paddocks which will have more than 3000kg DM/ha before they are due to be eaten are likely candidates.

If left to be grazed, the energy in the grass will be falling and the fibre content will go up which is not what calving cows with limited rumen space need.

Make sure paddocks are free of stumps, tomos and anything that shouldn’t be there. If there are hazards tell the tractor drivers so they know to stay clear.

Walk the paddock to check there are no forgotten standards or waratahs. One of those in a mower is not pretty.

Hopefully the weather will behave and you can cut after a couple of days of sunshine so energy in the grass will be extra high.

Cutting the grass at the right height is essential – you are trying to make the best silage possible, not deck the paddock so leave the dead matter behind and any dirt.

Aim to wilt it in less than 24 hours aiming for a dry matter (DM) content of between 25% and 30%. You can tell by squeezing the wilted grass – if it’s right your hand will be wet but there won’t be liquid running out. And it stays in a compacted damp ball afterwards.

If it’s less than 25% DM, your chop length should be about 8cm to 10cm. If higher than 30% it should be a lot shorter – 2.5cm. If it’s in between, where it should be, go for about 5cm.

This makes sure you get it can get it compacted correctly in the stack.

Once the grass is harvested, it’s all about making sure fermentation happens and your high quality grass turns into high quality silage and not something else.

The bacteria in the grass gets busy converting the plant energy (sugars) into acid. Silage is pickled grass – the acid drops the pH of the grass and preserves the silage.

The quicker this happens the higher the quality of the silage and the lower the losses. Your cows will also love it and you more.

It’s best to give the process a helping hand, instead of leaving it up to nature, by using an inoculant.

Inoculants contain the best bacteria for converting plant sugars into acid.

There are two main types of inoculant – one for fermentation (for the start of the process) and one for stabilising silage (the end of the process).

Fermentation inoculants mainly contain lactic-acid-producing live bacteria which speed up fermentation. They’re especially useful when the weather hasn’t been great and your grass could be better.

They quickly lower the pH level of the silage and help inhibit undesirable fermentation of microorganisms like Clostridia and Enterobacteria.

They also help to create a more efficient fermentation to give you high energy silage and they can reduce proteolysis which is the breakdown of proteins.

Stabilising inoculants contain such bacteria as L Buchneri which preserves silage, helping to stop mould growths and the stack over-heating when you open it back up to feed it out.

Some inoculants are a combination of both.

Get the inoculant on the harvested grass evenly (either at the chopper or on the stack).

If applying it at the chopper, check the spray nozzles several times a day to make sure they aren’t blocked and the application rate is correct for the tonnage harvested.

If applying it on the stack with a hand sprayer again try to get it as even as possible.

Be careful storing the stuff – the bacteria in them is alive so they don’t like getting heated up and the tank should be away from the engine of the chopper. Read the instructions on the packet.

The last thing that is left for you to do is to make sure there is the least amount of air in the stack as possible.

Oxygen stops the fermentation process as the good bacteria you want in your stack converting the plant sugars to acids are anaerobic which means them and oxygen just don’t get on.

Roll the pit to get air out and seal it well with a weather-proof cover but don’t over pack wetter material or it will go to slush.

Put enough tyres on the stack so they are touching all over it, not just around the edges.

Done. Let those bacteria get to work!

But don’t walk away and forget about it. Check often to make sure the stack is not leaking liquid and if it is, do something about it straight away.

Liquid from silage stacks is lethal in waterways so you must contain it somehow. Make sure concrete bunkers are not cracked, tanks are not full and collection channels are running and not blocked.

The effluent can be spread on pasture where there is no risk of run off but dilute it 1:1 so you don’t burn your grass.

Silage takes a month or so to be ready and when you open your stack it should smell sweet with almost a tobacco smell (cows can smell it kilometres away).

It should have lots of leaf, with very little stem and be green, yellow or pale brown.

If it’s dark brown or black and smells rancid you’ve produced something more like compost than silage.

Check also for moulds and fungi – some of them produce mycotoxins which can reduce feed intake, cause impaired immunity in your cows and disrupt fertility.

You can get it tested for energy and protein. Good silage should have about 30%DM, 11MJ/kg DM ME, 70% true protein and a pH of 4.

A well-covered stack.