Economic benefits of feeding maize grain

Milk response rates (DM or energy basis)

The response rate to supplements varies depending on a number of factors including the type of supplement, the time of the year when it is fed, pasture cover levels and the total drymatter intake.

Strategic feeding (e.g. using feeds to extend lactation or to fill feed deficits during the lactation) will normally generate a higher milksolids response rate than feeding continuously throughout the lactation.

DairyNZ’s Facts and Figures for New Zealand Dairy Farmers12 gives a range of possible response rates to good quality supplements (>10.5ME ) fed with low (<15%) wastage (Table 4)


Table 4. Seasonal milksolids response to supplements (on a drymatter and energy (MJME) basis)12
Time of Season Milk response rate*
  (gMS/MJME)  (gMS/kgDM)@11MJME
Spring 8.0-12.0 90-130
Summer 7.5-11.0 90-120
Autumn 7.0-8.0 80-90

* Residuals

Data collected from 60 seasonal supply farms situated in the lower North Island and South Island was used to determine the response to grain being achieved under commercial conditions15. On average the farms fed 179 kg grain per cow per year with the range between 0-952 kg/cow/lactation. Average milksolids production was 435 kgMS/cow with a range from 310-595 kgMS/cow. The average response to grain was 88g MS/kgDM fed in the 2009-10 season and 146g MS/kg fed in the 2010-11 season. The average response over the two years was 117g MS/kgDM grain. The short-term response to grain varied between seasons with the response rates being:

  • Spring (50 - 54g/kgDM grain fed).
  • Summer (141 - 193g MS/kgDM grain fed).
  • Autumn (116 - 138g MS/kgDM grain)15.

Milksolids response of cows fed grain

A number of New Zealand trials have measured the milksolids response of cows fed grain:

  • In the 1.75 t MS /ha trial, Herd 6 was fed a total of 1,247kg maize grain per cow during the lactation. The milksolids response rate was 99g MS/kg DM fed or 7.6g MS/MJME13.
  • Penno et al . (1996) offered rolled maize to grazing dairy cows in a two year farm-let experiment. At a stocking rate of 3.24 Friesian cows per hectare annual milk yields were increased by 76g MS/kgDM of grain fed. When stocking rates were increased to 4.48 cows per hectare annual response rate was increased to 88 gMS/kgDM grain fed14.
  • In a further farmlet trial Friesian cows stocked at 4.41 cows per ha conducted over three complete seasons the milksolids response was 96g MS/kgDM grain. Penno concluded that full lactation responses of 7.5g MS/MJME can be expected when grain is offered to dairy cows grazing restricted amounts of pasture14.


*Adapted from Roche and Hedley, 2011. Supplements – the facts to help improve your bottom line. DairyNZ Technical Series July, 2011 p 6-10. Assumes grazing residuals of 1,500-1,600 kgDM (7-8 clicks on RPM). Responses decline when residuals are higher than 1,600 kgDM (i.e. cows are better fed). For a full list of assumptions see

12 Dairy NZ, 2010. Facts and Figures For New Zealand Dairy Farmers pg 32-33.

13 Macdonald, K. 1999. Determining how to make inputs increase your economic farm surplus., Ruakura Farmers

14 Penno, J.W.; Bryant, A.M.; Macdonald, K.A. 1996. Effect of nitrogen fertiliser and supplements on pasture production and milksolids yield from dairy farm systems. Proceedings of the New Zealand Society of Animal Production

15 De Klerk, H. 2012. Milk Response to grain achieved by NZ pasture based farmers. SIDE Conference Proceedings pg. 327 - 341.