Silage Pasture

Silage is basically the preservation of pasture during a time of pasture surplus for feeding to stock at a time when pastures are in low supply or at times when pasture conservation is required

Purpose and questions to ask yourself:

· Why or for what reason are you making pasture silage?

· Where is it going to fit it into your feeding program?

· Is it going to be your main supplement?

· Is it to provide protein?

· Is it to provide energy

· What is it going to supplement? Eg spring pasture, summer pasture or autumn pasture

These are all questions we need to sort out to enable us to optimise the real value of our silage.

Protein: Grass silage can be used to provide a good source of protein to help maintain milk production during times of pasture stress/limitation as well as for maintaining end of season production while increasing your winter pasture bank. Protein and ME levels generally go together – high protein silage means high energy, low protein silage means low energy. Pasture silage protein levels vary considerably from 7% to 25% so important to understand your product and how are you going to get the best out of it

Understand the ensiling/preservation process:

Exclusion of air/oxygen when making is the main consideration. Once the air is excluded we have preservation, if we don’t exclude air/oxygen we end up with decomposition.

Air means the presence of Oxygen equals an Aerobic environment equal’s decomposition. So the longer air is present the lower quality silage due to continued decomposition

Oxygen promotes the activity of Clostridium organisms. These are putrefying organisms. The result is that bad smell from silage that stays on your boots

Wastage is high. To allow the presence of air in your silage means a waste of your time and resources.

No oxygen equals an anaerobic environment equals preservation equals higher levels of lactic acid.

Oxygen must be excluded until the day of feeding to maintain preservation and prevent decomposition

The introduction of oxygen at any stage will start decomposition.

Mature stalky, drier pasture is more difficult to compact and more often than not results in poorer quality silage.

PH: This is a good indication of silage quality, ideally should be between 4 to 4.4pH as the pH goes higher towards 5.0 pH it normally indicates poorer quality, infact silage with a 5.0 is very poor quality

PH: The ideal for pasture silage is between 4.2 and 4.8. Below or above altars the fermentation processes quality and palatability. Immature pasture will give a low pH and an over mature pasture will give a high pH. Silage with a high pH is unpalatable to stock


Ideally avoid rain or wet days. I have often heard it said that silage can be cut in the rain, it doesn’t matter, but in fact it does. Cutting wet or during wet weather can have a seriously detrimental effect on both protein and energy levels. It only takes one day’s rain to lower the ME from 10.5 to 8.5 and we also see a serious decrease in protein eg 16% down to 12% protein. One day’s rain after cutting can turn good quality pasture silage into an average one, from one that will support milk production into one that will only be suitable for maintenance.

Ideally cutting in the afternoon following a day’s sun can also increase quality = increased sugars and lower nitrates

My policy is that if your contractor arrives to cut and the weather is wet or looks like rain then close the gate. It’s your silage you are in control of quality; this is my advice to all clients

The next step – preservation:

1 Compaction. Rolling when stacking or baling and wrapping.

2 (a) Air (oxygen) heat is produced

(b) Oxygen exclusion (secondary) – Heat producing bacteria use available

oxygen which once used immediately brings heating to a stop as long as

there is no more air available to enable heat production to continue.

(c) Preservation starts at this point

3 Maintaining oxygen (air) exclusion to maintain preservation


Stacking/pits: The traditional stack, this was before pits were round. A thick layer of soil was placed on top following harvest, both for weight and for the exclusion of air. It is interesting to note that until the early 60’s generated heat in the stack was considered an important part of silage making. Harvesting was done in stages so as to maximise heat levels, thermometers were use to monitor temperatures. Interestingly protected or bypass protein was high in silage made this way. We changed as research decided it wasn’t necessary but the question remains open, also as before if oxygen was present then there was greater decomposition

With stack/pits the presence of moisture is an important factor for the exclusion of air, if the pasture is too dry when ensile it is very difficult to exclude all the air and so there is likely to be more decomposition resulting in a higher pH and lower palatability. 70% to 75% moisture, 25to 30% DM is ideal for stacked silage noting the higher moisture requirement for air exclusion.

Stacks are rolled with heavy machinery during and after the completion of the harvest. This excludes the air and the higher presence of moisture prevents any re penetration of air/oxygen. Good covering and weights also prevent the return of air and minimise wastage. Without good covering up 1/3rd of the stack could be lost to wastage, just think of all those wasted harvest days and cost you put into wastage if the job is not completed

Wrapped: The baling process excludes much of the oxygen and the wrapping prevents more oxygen moving back into the bale thus the importance of wrapping as soon as possible after baling. As the silage heats the last of the oxygen is quickly consumed and preservation quickly takes place. Delayed wrapping reduces quality especially palatability.

As moisture, in this process, is not important for preservation the pasture can be wilted to a higher dry matter content. Ideally 50% moisture, 50% dry matter. As moisture cannot drain from the wrapping, baling with high moisture content will result in a soggy bale and provide unnecessary weight. Plus also we see a reduction in quality.

Single Bag: Similar to wrapping only the exclusion of air can be more difficult.

Maize/corn Silage: As the dryness of the maize plant makes it very difficult to compact, the only to way achieve optimum compaction is to fine chop. Due to the texture of the finished product and difficulty in getting optimum air exclusion a pit or bun type stack is used for storage to ensure that all air is actually excluded. Pits can be in the ground or made with concrete walls etc. Silage inoculants are beneficial

Covering of maize/corn silage is critical for a good end product.

Moulds can move up to a metre into an uncovered stack within 24 hours so be aware

When to harvest:

The kernel can used to determine the right time for conservation.

Break off a kernel and look at the milk line. This is a line that moves down the kernel as it dries, one part of the kernel can show as white.

The plant is ready for conservation when this line has moved one-third to one half way down the kernel. This will give the greatest energy level and stock performance from the end product. Also the level of moisture in the kernel affects the total fermentation process.

Note that the kernel dries down through the plant to the root system not through the skin into the atmosphere.

I have seen maize silage made from the plant without the kernels, here we end up with a very low quality, low palatability silage, the kernel is essential for the optimum fermentation process and optimum quality

The drier the kernel the finer you need to set the chopper

The production of lactic acid is very important in maize silage.


Smell test: This is a good test of quality. Rub your hands with the silage and in a few minutes there should be no smell residue on your hand, if there is then you know that the quality is questionable.

Lactic acid has a sour smell.

General – quality – protein levels can be affected by

Type of pasture

1. Species – Rye grass can make good silage but is often mineral poor. A good clover rye grass mix will contain higher levels of calcium and magnesium and is generally lower in ammonia. Timothy pasture is generally of good quality but lower in protein (Northern Hemisphere)

2. Density of pasture – amount of base in a pasture will increase quality, mature pasture with too much stalk will reduce quality

3. Stage of growth – affects protein/energy level/compaction/nutrient

4. Balance of species. Legume/grass balance. Affects protein/energy/nutrient content. Higher legume content =’s easier compaction and increased quality but can be lower volume.

5. If pasture is too fresh this can mean a higher level of acidity and higher levels of ammonia and often poorer fermentation. There will be greater nutrient loss due to drainage from the stack/pit

Energy: Maize silage is an excellent form of energy/carbohydrates for which to supplement fresh high protein spring, autumn and winter pasture and any irrigated pasture.

Maize silage is generally lower in calcium and phosphorus. 70 to 150gms of lime flour per head per day are usually added when feeding.

Maize silage is low protein so is not suitable as a total feed for young stock or to maintain milk production when there is little pasture – you must add a high protein supplement to your maize silage eg pasture silage if available


These are used to increase the levels of desirable organisms so that the fermentation process is more complete.

Bryan L McLeod

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