Pasture is the major component of the New Zealand dairy cow’s diet. However, opportunities exist to improve profit through the strategic use of maize silage.
The pastoral dairy farm is a balance between pasture supply and cow demand, which must be maintained to achieve efficient conversion of feed into milk and profit.
Unless well integrated with pasture supply and feed demand, extra feeds such as maize silage, will produce extra milk, but not always extra profit.
To use maize silage profitably, farmers must identify what they are trying to achieve through its use. This requires working out the key limiting factors for running an efficient and profitable grass-based system, and whether changes are in line with their goals. This can be done in conjunction with a farm consultant or forage specialist.
A key driver of response to additional feed is energy deficit, the difference between energy demand and the actual energy supplied. Cows of high breeding worth, at high stocking rates and with lactations longer than 260 days, are more likely to be in energy deficit, and will be more responsive to additional feeds such as maize silage. Cows respond best to extra feed if the farm has a genuine feed deficit, created through calving earlier, more days in milk or carrying more cows per hectare.
If all of the additional energy provided by supplement is converted into milk, the maximum possible response is 13g MS/MJ metabolisable energy. This is equivalent to 137g MS/kg DM maize silage (assuming maize silage is 10.5 MJ ME/kg DM).
In practice, responses are usually much lower than this due to feed losses in transport, storage and feeding, the substitution of supplement for pasture, the partitioning of energy into live weight gain or the maintenance of extra cows.
Trials in New Zealand have found production responses to maize silage 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 New Zealand dairy farms found on average, that supplements fed added only 50g MS/kg DM to annual milk solids per cow, and 96g MS/kg DM to annual milk solids/ha.
With such a variation in response possible, attention to detail is required in order to turn additional feed into additional profit.
Maize cost can vary depending on where and how it is grown. If maize is grown on the dairy platform in an effluent paddock, the cost could be low. But maize purchased off-farm is generally more expensive.
However, allowance needs to be made for the value of the extra nutrients bought in with the maize and a reduction of risk due to maize being grown off the dairy platform.
On-farm management of feed potentially causes the greatest variation in feed costs. For example, a poorly managed stack can cause wastage amounting to a 30 per cent increase in feed costs. Also, grass wasted through feeding maize silage at the wrong time can result in reduced profitability.
Source: the Foundation for Arable Research publication ‘Best Management Practices for Growing Maize on Dairy Farms’. A free copy of the book is available by emailing: firstname.lastname@example.org or phoning 03 345 5783. Or go to: www.far.org.nz/index.php/far-publications/entry/best-management-practices-for-growing-maize-on-dairy-farms