Exploring results from the FVI trial

To help farmers choose the best-performing ryegrass cultivars for their region, DairyNZ and research partners began developing the Forage Value Index (FVI) in 2012. The online tool uses a five-star rating system for cultivars, with ratings based on dry matter yield performance data from small plot trials, and the estimated economic value of additional feed grown.

DairyNZ senior scientist Wendy Griffiths says that, since 2018, DairyNZ has tested the FVI under realistic farm conditions to see how farm system results stack up against predictions. The tests compare low-FVI (1- and 2-star) and high-FVI (4- and 5-star) perennial ryegrasses (diploid, common endophyte).

“We were expecting the milk production from cows grazing the high-FVI perennial ryegrasses would be greater than from those grazing the low ones but, surprisingly, that was not the case,” says Wendy.

The Waikato trial site experienced dry summers, with January and February rainfall at about half of the 30-year average. This affected pasture growth and persistence, so the additional days in milk predicted from the high-FVI group did not occur. However, this does not appear to be the only factor at play.

“For the Upper North Island, we were expecting operating profit from the high FVI group to be $300-$400/ha greater than the low-FVI group. The trial didn't achieve these predictions, so we're now developing the next phase to address why,” says Wendy.

The team is now planning a deep dive into the data to identify the reasons for the trial results, exploring:

• climate impacts
• underlying Farmax modelling
• measurement methods for dry matter yield in plots and trials
• pasture quality
• plant-animal interactions
• scaling from plots to farmlets.

DairyNZ is confident the FVI approach, similar to the National Breeding Objective for animals, is the appropriate model to support plant breeding efforts and inform farmers about superior plant genetics in ryegrass cultivars.

“As soon as possible, we’ll share new knowledge with farmers so they can continue to make informed ryegrass cultivar selections. We’re continually reviewing and updating the FVI, and the results of this review will also feed into further improvements to the FVI,” says Wendy. Watch this space for further updates.

Key points

• The validation trial undertaken across four years found no significant differences in whole-season milk production between cows grazing high- and low-FVI perennial ryegrasses.
• The economic value for seasonal dry matter and seasonal metabolisable energy content traits will be revisited.
• DairyNZ will investigate the reasons for the results and share findings with farmers. Learn more about the results at dairynz.co.nz/fvi-research