How Much N Does Your Maize Crop Really Need?
Over the past few weeks, I’ve had several conversations about nitrogen (N) management in maize crops for the coming planting season.
This article provides some general guidelines based on typical autumn-winter pasture protein and mineral levels. Contact your local veterinarian or animal nutritionist for farm-specific results.
How much maize silage can you feed?
Maize silage is the ideal feed buffer because it can be fed in large amounts during extreme feed deficits. It is a high quality, palatable forage which provides excellent levels of carbohydrate (as maize grain starch) as well as digestible fibre (from the green portion of the plant). Cows will readily eat high amounts of maize silage, and the fibre makes it safer to feed when compared with concentrates such as grain or molasses which contain high carbohydrate but low fibre levels.
The low crude protein content of maize silage (about 8%) places a ceiling limit on the amount that can be fed before cows become protein deficient. Maize silage is also low in some macro minerals (e.g. calcium, magnesium, sodium and phosphorus).
The stage of lactation, the amount of maize silage fed and the amount and type of other feeds in the diet will determine whether mineral supplementation is required. The following recommendations are meant as a guideline only.
Farmers facing severe pasture shortages can further increase the amount of maize silage in the diet by feeding an alternative high protein supplement, e.g. soybean with 50% crude protein or canola meal with 37% crude protein.
In a crisis situation, it may be viable to accept a lower dietary protein level for a short time. Feeding too little protein may limit milk production or the rate of condition score gain. However, as long as energy intake meets target levels, cows should hold weight. Diets can be adjusted once pasture cover levels have increased to more normal levels.
Feeding management
Whether you are feeding moderate or high rates of maize silage, always follow the best practice guidelines for feeding management:
Where possible introduce maize silage slowly, starting at 1 - 2kgDM per cow and increasing 1 - 2kg DM every two to three days.
Make sure all animals have access to feed at the same time to reduce the risk of individual animals eating large amounts.
Discard mouldy or decomposed material from any feed.
In summary, maize silage is an excellent choice for feeding when pasture supply is short. High feeding rates are possible but watch crude protein and mineral levels, and ensure best-practice feeding guidelines are followed.
• Ian Williams is a Pioneer forage specialist. This email address is being protected from spambots. You need JavaScript enabled to view it.
