Maize for Silage
Insight 304


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Aim to keep the face of the maize silage stack tight throughout the feed-out period. You should not be able to push your fingers into the stack any further than the depth of your finger nails. Maize silage that is loose allows air to penetrate into the stack. Aerobic (oxygen loving) bacteria break down plant material producing waste products including carbon dioxide, heat and water. Silage quantity and quality are decreased.

Maize silage that is well compacted and sealed will not contain moulds. Moulds grow once the silage has been exposed to the air for a few days or more. Although not all moulds are harmful, some can cause animal health problems. Never feed mouldy or “rotten” silage to your cows.

Careful use of the tractor bucket at feed-out time will minimise the loosening of silage. If possible, use the bucket to chip down silage and then scoop it up from the ground. Avoid digging into the stack as this loosens silage that will not be fed for several days.

Figure 1 (below) shows a good bunker or stack management technique. The first step is to work out how far into the face you need to feed. Next scoop out the lowest section of the silage. Then using the bucket blade, chip down the silage one section at a time starting at the bottom.

Figure 1: Bunker or stack silage removal technique.

Another alternative is to move sideways across the bunker face removing small amounts of silage from the whole face.

Silage grabs and block cutters will assist in keeping the face of the stack or bunker tight.


It is not necessary to lower the silage cover if maize is being fed on a daily basis since it will be impossible to seal the stack and the air that is trapped under the stack tends to heat creating an ideal environment for the growth of mould.

The cover should be lowered during periods of heavy rain. If birds are a problem use shadecloth over the front of the stack.


Introduce maize silage into the diet over a period of 5 - 10 days. Start by allocating each animal 1 - 2 kg drymatter and increase the amount that you feed each day.  The reasons for gradually introducing maize silage into the diet are numerous.

The rumen of a cow will contain cellulose-digesting and also starch-digesting bacteria. Most of the sugars in grass are stored as cellulose whereas the grain in maize silage contains high levels of starch. Animals that have been fed totally on grass will have relatively low levels of the starch-digesting and high levels of the cellulose-digesting bacteria. Feeding large amounts of maize silage to cattle that have low levels of starch digesting bacteria will result in the inefficient use of the maize grain resulting in large amounts in the dung. A slow introduction will allow starch digesting bacteria levels to increase and will improve utilisation and minimise the risk of gastric disturbances or acidosis (grain overload).

Animals that have not been fed maize silage previously may take a few days to acquire a taste for it.  Feeding out large quantities of maize silage in the first few days may result in unnecessary wastage.


Once maize silage has been introduced to the diet, feed it on a daily basis. No feed will be efficiently used by an animal if it is being added to and removed from the diet at frequent intervals.

If you wish to feed out your maize silage up to one day in advance, use Pioneer® brand 11C33 maize silage specific inoculant. While silage can be fed immediately after harvest, maximum aerobic stability gains will be made when it is fermented 30 days prior to feeding. 

If you have not used 11C33, the best time to fill your feed-out wagon or bins is immediately prior to the time that you will feed the silage to your cows. 


Farmers are increasingly using feed pads for maize silage feeding.

Where a feed pad is not available maize silage can be fed-out using a feed-out wagon. The maize silage can be dumped in piles (by remaining stationary and allowing the silage to feed-out), in a line in the centre of the paddock or against a fence line. There are mixed opinions as to the benefits of piles vs. feeding in a line. The important point to note with either system is that there needs to be room for the entire herd to feed at once. Considerable wastage can occur if animals are fighting for a space.

The main benefit of putting maize silage in a line against a fence is that the animals cannot walk (and dung) on the silage. The same effect can be achieved if the maize silage is fed-out in a line across the paddock and an electric fence is erected down the centre. This latter option allows animals to feed from either side of the line of silage.

Minimise acid burn of pasture by feeding maize silage onto long pasture rather than onto a paddock that has been grazed out.


The metabolisable energy content (ME) of maize silage is largely determined by the percentage of grain present since grain contains 70% more energy than stover (the green part of the plant). Time of harvest, fermentation quality and feed-out management will also have an effect on energy content. The average ME content of New Zealand maize silage is around 10.8 MJME/kgDM. Some well fermented, high grain content maize silages have metabolisable energy levels in excess of 11 MJME/kgDM.

Maize silage is a low crude protein content feedstuff. This makes it an ideal complement to high protein pastures in the spring and autumn periods. During the summer when pasture protein levels can fall, maize silage feeding levels should be carefully monitored. Feeding too much low protein maize silage may result in animals holding or gaining liveweight rather than putting milk in the vat. Feeding a small amount of maize silage for several weeks is a better option than feeding a large amount of maize silage with low protein pasture. If pasture is limiting, consider feeding maize silage in conjunction with another protein source such as lucerne, a leafy forage sorghum crop, or high quality pasture silage.

Maize silage can be used to help improve the dietary cation:anion difference (DCAD) of a ration because it contains low levels of the positive ions calcium, sodium, magnesium and potassium. This is particularly important for cows 3 - 6 weeks away from calving since a low DCAD diet initiates the calcium metabolism process. Cows that are fed diets that are low in positive ions and high in negative ions (anions) such as chlorine, sulphur and phosphorus must produce their own cations to maintain a neutral charge. Hence the cow mobilises body calcium reserves to maintain a neutral charge. When the cow calves and her calcium requirement increases because she is lactating, the calcium mobilisation process has already been initiated. Consequently there is a decreased incidence of milk fever, increased milk production and improved reproductive performance.


Dietary mineral supplements should be considered especially during early lactation or if a large proportion of the cow’s drymatter intake is maize silage. Use the following table as a guide. Mineral supplementation is not expensive but can make a significant difference in milk production levels if the mineral is lacking.

Use the following mineral supplementation guidelines when 20 - 40% of the drymatter intake is maize silage and the balance of the diet is pasture. For mineral recommendations specific to your farm, or for maize silage feeding levels above 40% of the dietary drymatter intake, contact your animal nutritionist or veterinarian.

Stage of lactationLimeflour (supplies calcium)Magnesium oxide (supplies magnesium)Agsalt
(supplies sodium)
Pre-calving 0 40 0
Early lactation 60-150 40-70 15-30
Mid Lactation 0-60 40 15-30
Late lactation 0-60 40-60 20-50

Minerals can be topdressed onto the silage once it has been fed-out in the paddock or placed in bins. Alternatively they can be added to the feed-out wagon either in layers or on the top of the silage. Feed-out wagons will mix the minerals into the silage to varying degrees. Check that the application system that you are using results in the minerals being evenly distributed through the silage.

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Revised: June 2015
Expires: June 2018