Back Minerals and maize silage

Date: 21 July 2016

Many New Zealand cows suffer macro-mineral (calcium, phosphorus, magnesium or sodium) deficiencies sometime during the season. This occurs because pasture mineral content varies significantly depending on a large number of variables including weather conditions, soil type and fertility, pasture species mix and distance from the coast.

While maize silage contains excellent energy levels, it is relatively low in calcium, phosphorus, magnesium and sodium. Feeding maize silage, can sometimes result in macro-mineral shortages or it can exacerbate a shortage which already exists. Macro-mineral supplementation is generally not expensive but can make a significant difference in milk production levels if the mineral is lacking.

Dietary mineral supplements should be considered especially during early lactation or if a large proportion of the cow’s drymatter intake is maize silage. Table 1 provides a guideline for mineral supplementation when 20 - 40% of the drymatter intake is maize silage and the balance of the diet is pasture.

For accurate mineral recommendations which are specific to your herd and farm, or for a mineral recommendation when you are feeding a mix of supplements or more than 40% of the dietary drymatter intake as maize silage, contact your animal nutritionist or veterinarian.

 Table 1: Mineral supplementation guidelines for cows fed up to 40% of the drymatter intake as maize silage and the balance as pasture.



Stage of lactation

Limeflour (supplies calcium)

Magnesium oxide (supplies magnesium)

Agsalt (supplies sodium)





Early lactation

60 - 150

40 - 70

15 - 30

Mid Lactation

0 - 60


15 - 30

Late lactation

0 - 60

40 - 60

20 - 50

Feeding minerals in maize silage results in much better utilisation than pasture dusting. Minerals can be topdressed onto the silage once it has been fed-out in bins or the paddock. 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.