The trial at Northland Agricultural Research Farm near Dargaville aimed to answer whether we can reduce reliance on imported feed and still maintain profitability and sustainability with a volatile climate and milk price. Completed this year, the trial compared three farmlets with different feed inputs – one with pasture only, one with crops grown on-farm and the other supplementing with palm kernel expeller (PKE).

Farm manager Kate Reed and trustee Kerry Chestnut present trial updates at a Northland Agricultural Research Farm field day.

In the first two years of the study, when costs associated with supplementary feeding and cropping were considered, the pasture-only farm system had similar or better profitability than the system using PKE. The PKE farm was more profitable in the third season, with a prolonged wet period during spring having a greater impact on the grass-only and crop farmlet.

The cropping farm had the lowest profit in all three seasons. Having more than 20 percent of the farm out in crops each year put significant feed pressure on the rest of the farm and led to the full costs of home grown crops being captured. Wet winter and spring conditions also affected both crop production and pasture utilisation on the heavy clay soils.

Former DairyNZ principal scientist Dr John Roche, who supported the trial, says it highlighted the costs associated with increasing production by adding more feed into the system.

“The cost of the marginal milk produced by increasing stocking rate and bringing in extra feed, is very high. That cost is dependent on the response to supplements, but the data would indicate that the response to supplements has to be over 110 grams of milksolids per kilogram of supplement dry matter (g MS/kg DM) and the milk price must be greater than $6.50/kg Milksolids for that supplementary feed to produce profitable milk,” says John, who recently moved into a role as departmental science advisor for the Ministry for Primary Industries (MPI).

“That wasn’t properly understood before we did this experiment, but we’ve been doing other work at the same time, reviewing farm systems experiments. The same conclusion would be drawn: that the cost of the marginal milk from increasing stocking rate and bringing in feed to produce more milksolids per hectare is very expensive.

"Over all three seasons, the pasture-only farm was close to the PKE farm in profit. There are a lot of hidden costs associated with increasing production through putting more feed into the system. This project has allowed us to put some numbers on the less-tangible costs."

Response to supplements

Supplementary feed did offer a tactical advantage to the higher-stocked herd during the exceptionally wet winter and spring of 2017; however, these results need to be viewed in context. John says the Northland trial had an unusually high milksolids response, especially in the 2017/18 season. The PKE response at the Northland Agricultural Research Farm was 126g MS/kg PKE DM. In comparison, the average response in DairyBase is about 80g MS/kg supplement DM.

“This year’s response was as high as we were going to get. We would very rarely see a response like we saw last year,” says John.

“Also, through good management and better summer growing conditions, we limited the use of supplements to about 500kg DM PKE/cow and produced 1100kg MS/ha on the PKE farmlet during the trial. In comparison, over the preceding three years (prior to commencing this experiment), the farm used more than one tonne of DM/cow of supplement to produce 1154kg MS/ha.”

An overview of the Northland Agricultural Research Farm, showing one of the three herds.

Farmers’ input

The trial, largely funded by DairyNZ and the Ministry for Primary Industries’ (MPI) Sustainable Farming Fund, was set up by Northland Dairy Development Trust.

The Trust was formed in 2006 to support farmers in securing quality dairy research relevant to Northland. The Trust’s committee is largely made up of dairy farmers who have input into the research carried out on the Northland Agricultural Research Farm. John says the input of the farmers was invaluable.

“The committee put in a huge amount of time and personal energy and the result is a world-class experiment in the region. It doesn’t matter how busy they are in winter or spring; we have four or five farmers at every one of the fortnightly meetings and quite often we could have 10 or 12,” says John.

A new trial, building on the research from the imported feed trial, will provide information to help farmers manage their feed evaluation index (FEI) in a variable climate.

For more information on the research from Northland Dairy Development Trust visit nddt.nz

Average of the three-year trial/annum

• The pasture-only farmlet (2.6 cows/ha) generated an operating profit of $2006/ha and production of 909kg MS/ha.
• The cropping farmlet (2.8 cows/ha) generated an operating profit of $1554/ha and produced 996kg MS/ha.
• The PKE farmlet (2.8 cows/ha) and with 500kg DM PKE/cow, produced $2281/ha operating profit and 1091kg MS/ha. The average response to PKE was 126g MS/kg DM, with a range from 107 to 147g MS/kg PKE DM.

This article was originally published in Inside Dairy August 2018