With feed bills generally one of the “big four” areas of expenditure in most farm budgets, getting bang for the buck is critical, and poor quality maize silage would probably cost a similar amount to the good stuff.
Ian Williams, a forage and farm systems specialist with Pioneer, gave the Dairy Exporter a few pointers on making good quality maize silage.
How you cut and dice it
Harvest management could have a major impact on the final quality of the silage.
“The amount of starch increases quite dramatically as the plant goes towards about 30% whole plant drymatter, but at the same time the plant is drying down as well,” Williams said.
Harvesting at the right time was a balancing act between maximising starch and not letting the plant get too dry. Too early would mean relatively lower starch values and a higher potential for leachate from the ensiling process, although a longer chop length could mitigate that to an extent. Harvesting too late meant a loss in digestibility as the fibre in the leaves and stalks increased. Compaction was also more difficult with a dry crop.
Williams recommended a target drymatter range of 30-38%.
“If it’s a greener plant we can take it up to 38%. But if it’s a drier plant we might be harvesting at 32-34% to help with the ensiling process.”
“To a certain extent, with modern-day plant processing machinery, we can make a silk purse out of a sow’s ear. That enables us to kernel process and change the chop length.”
Kernel processors made sure at least 80% of kernels were broken into at least four pieces. Processing the cobs and kernels improved digestibility and made the starch easier to degrade in the rumen.
The ideal chop length sits at about 10-15mm, though particles will be shorter and longer than that in any silage. A shorter chop length – 5-9mm – can be used if drymatter exceeded 38%. A longer chop length of up to 20mm could be used in very wet crops – where drymatter was less than 30%.
A simple squeeze test could operate as a rule of thumb for checking the right chop length was being used. This was where a handful of maize silage was taken and squeezed – the hand should be moist. If water was visibly squeezed from the handful, the chop length should be increased. If there was no obvious moisture and the silage didn’t stay compressed when released, the chop length should be shortened.
This test should be done early in the harvest process so changes could be made if required.
Inoculation
Inoculants are bacteria selected to speed up fermentation and make the process more efficient.
“The bacteria are incredibly efficient at converting the sugars and starch in the plant into lactic acid. This drops the pH quickly. And the quicker the pH drops down to 3.4-3.6, the less drymatter loss occurs through the ensiling process.”
Because the inoculant increased the speed of the ensiling process, the silage could be fed out earlier than non-inoculated maize silage. Williams said it could be fed 3-4 days after covering the stack. However, going into the silage early did have a consequence.
“The longer you leave it, the more available the starch becomes. You get a real rapid increase in the availability of starch for about the first six weeks, and then it begins to tail off.
“If you’ve got the ability to leave it six weeks before opening it, that’s ideal. But you can get into it straight away, no problem.”
Compaction, compaction, compaction and covers
The bacteria involved in the ensiling process thrive in an anaerobic – oxygen-free – environment. That is why compacting the stack properly was so important for obtaining a good result, Williams said.
The same theory applied to the cover. Tyres should be touching each other for the best results, and Williams recommended sealing the edges of the cover with dirt or sand.
“Once that happens, those little bugs start chewing up any oxygen that there is and go anaerobic and produce lactic acid. And then that silage is stable forever. As long as the air is kept out, that stuff will stay stable forever.”
Managing the face
Opening the stack for feeding out obviously exposed the silage to oxygen. Minimising that exposure minimised wastage.
“As soon as you loosen the face you’ve got air going in. Air creates moulds and mildews, and then the pH goes up. Once the pH goes up, stuff starts to heat. When stuff starts to heat, it goes into compost.”
Williams said ideally the aim should be to go across the face of the silage stack once every two days, although once every three days was acceptable. Constructing the right size stack for the way the maize would be used – early season when cow numbers building versus later on when all cows in-milk – could play an important part in maintaining silage quality.
Ten rules for better maize silage
- Have the right sized bunker or stack for the job.
- Make sure rainwater run-off drains away from the stack.
- Harvest at the right drymatter content – between 30% and 38%.
- Use the right inoculant.
- Get the right chop length for the crop.
- Ensile the crop quickly.
- Compact. Compact. Compact.
- Seal cover edges and any joins securely.
- Stock-proof the stack.
- Use rat bait around the stack area up to one month before harvest to reduce the pest burden.
Testing maize silage drymatter
An estimate of the drymatter percentage in maize silage or potential maize silage can be calculated by using a humble microwave.
If testing maize that is already chopped and stacked, take 10 handfuls from a part of a recently exposed face. If testing a standing crop, take several plants from different places in the crop that are more than 20 rows from the edge, and chop into 15mm pieces. In both situations, the samples – either handfuls or plants – should be mixed well before being sub-sampled.
Pioneer guidelines suggest using the “quartering” method to get a workable but still representative sub-sample. Quartering involves placing the material on a flat surface in a circle, then use a ruler to break into quarters. Two of the “quarters” are discarded with the remaining two re-combined. The process is repeated until a sample of 100-200g is left.
A tare weight using a microwave-safe plate or previously dried paper plate is obtained, and a wet weight for the maize sample. The maize sample should be spread in a thin layer on the plate and put in the microwave, with half a glass of water in the back corner. The water level in the glass should be kept at a constant level and topped up as required through the drying process.
Initially, the sample should be heated for 3-4 minutes. If almost dry, a weight can be recorded. Then the sample should be stirred before being heated for another minute. After another weight is recorded, the sample should be heated for 30-second intervals until the weight doesn’t decrease by more than 2g. If the sample becomes charred, Pioneer guidelines recommend using the last recorded weight as the dry weight.
To calculate the drymatter percentage, divide the dry weight by the wet weight and multiply the answer by 100.
Practice and experience will streamline the process although there will be variation in drying times depending on sample size and microwave power.
