Maize Silage

Maize silage is a maize crop cut and ensiled in a stack or bunker. It is commonly used as a supplement to pasture in situations where cows would otherwise be underfed.

Maize silage is a high quality forage supplement. However, it is particularly low in sodium (Na), calcium (Ca) and phosphorus (P), and can be used as an effective carrier to supplement cows with magnesium (Mg).  

Maize silage is a useful supplement for filling genuine feed deficits, but needs to be well managed to reduce costs and wastage. New Zealand trials have found production responses to maize silage range between 32g MS/kg DM and 178g MS/kg DM. The highest response came from more days in milk created by feeding maize silage in a year affected by a dry summer. Analysis of more than 600 NZ dairy farms found on average, that supplements fed added only 50 g MS/kgDM to annual milksolids/ cow and 96 g MS/kgDM to annual milksolids/ha. With such variation in response possible, attention to detail is required to turn additional fed into additional profit.

Why is maize ensiled?

Maize silage is full of soluble carbohydrates which while being a great food for cows, is also loved by spoilage bugs, such as yeasts and mould. The aim of the ensiling process is to get air out of the stack and keep it out until maize silage is ready to be fed.

Storing maize silage

To minimise losses:

• Consider stack location and prepare site in advance of harvest. Consider environmental implications, e.g. risk of runoff, distance to waterways, drains and other sensitive areas.
• Consider whether to use a bun (stack) or a bunker. Buns can be located around the farm and therefore more flexible, whereas bunkers are initially more expensive but have higher compaction rate and therefore less wastage.
• Stack dimensions, the aim is to build a stack so that when being fed out, as little maize as possible is exposed to air. Consider quantity of maize, how many animals you are feeding and what inoculant you are using. Ideally it should take no more than three days to feed across the stack face, taking about half a metre each feed.
• Cover immediately after contractor has finished rolling the maize. Seal around the base of the stack with soil, sand or lime and place tyres to completely cover stack.

Feeding out maize silage

When you start feeding maize open the stack at the opposite end of the prevailing wind to prevent air getting pushed under the cover. Use a front end loader to create a face. Once the face has been created, chip away from the top to the bottom of the stack, rather than lifting from the bottom of the stack face. Don’t ram bucket or silage forks into the face of the stack as this creates shatter and may allow air to penetrate the maize stack.

Face management

Ensure the face is left tight daily, with no loose material at the base of the stack. A wide mouth shovel and a broom will help prevent this. You do not need to drop the cover down over the face each day. If birds are a problem can use bird netting or shade cloth.

Closing a stack down

Use the front end loader to remove any loose material from the front of the stack, trim up the face using an old chainsaw and spray a saturated salt solution over the stack face, drop the silage cover back down the face, reseal the base with soil and place tyres against the covered face. Replenish bait stations and leave stack until you need to feed out again. When you roll back the cover to feed out again, remove any material that may have become mouldy.

Maize Forage Trading Code of Practice

The ‘Maize Forage Trading Code of Practice’ has been designed to safeguard both the buyer and seller of maize. Standard protocols for weighing, sampling, and testing have been developed for trading on a dry weight basis (kg DM).

If you are not trading, the sample protocols can be used for determining the total DM yield for feed budgeting purposes. As well as DM %, the samples can also be tested for feed quality and nutrient content.

The complete code, good practice guide and the purchase contract are available from the Foundation of Arable Research.

Mineral additives to maize silage

Use the following mineral supplementation guidelines when 25-40% of the DM intake is maize silage. Contact an animal nutritionist to get recommendations when maize is more than 40% of the diet.