David Chapman, DairyNZ principal scientist.

The quest to find pasture and crop options that can surpass perennial ryegrass/white clover for production and profit is important for the future sustainability of our dairy sector. A recent example of this work is a DairyNZ farmlet experiment at Scott Farm, Waikato. This project aimed to produce 25 tonnes of dry matter per hectare (t DM/ha) from grazed forages – 20 to 30 percent above what the best farms are currently producing – while also achieving increases in milk production and profit¹.

Testing two approaches

Two approaches to the 25t DM/ha target were compared separately, and in combination, for three years.

Our first approach was to change the ‘base’ pasture from perennial ryegrass/white clover (PR/WC) to tall fescue/white clover (TF/WC), to exploit the better drought and heat stress tolerance of tall fescue.

Our second approach was to grow high-yielding, high-quality, summer-active forage crops on 20 percent of the farmlet to support high milk production through summer, when perennial ryegrass struggles to deliver enough high-quality feed. Two options were compared: chicory/red clover mixture (CH/RC) and lucerne (LU).

Combining the two approaches resulted in six farmlets, each stocked at 3.5 cows/ha: two base pasture types (PR/WC, TF/WC) each with three summer crop options (nil, CH/RC and LU).

What were the results?

The TF/WC pasture grew an average of 22.4t DM/ha/year versus 19.5t DM/ha/year for PR/WC. However, milksolids (MS) production and estimated operating profit were lower: 1370kg MS/ha and $4320/ha for TF/WC, versus 1390kg MS/ha and $4475/ha for PR/WC.

The shortfall in MS production and profit in TF/WC was due to the lower yield and nutritive value of tall fescue compared with perennial ryegrass during spring, resulting in lower daily MS production. The deficit in spring production was not recovered, despite greater growth from TF/WC during summer and autumn.

Incorporating crops reduced both annual DM yield and MS production. This lowered farm income. It also increased operating expenses associated with crop renewal and additional supplementary feed purchased to meet feed demand.

In summary

For this Waikato experiment, we nearly achieved the 25t DM/ ha target by changing the forage base from perennial ryegrass to tall fescue. However, the ‘drag’ of poorer feed quality from tall fescue-based pastures and/or higher costs of summer cropping with special-purpose grazeable forages meant animal production and profit were lower than the industry standard system based on PR/WC.

Additional summer growth from crops, such as this chicory/red clover mixture, wasn’t enough to cover extra costs and the loss of spring DM yield.

Reference

1. Lee, J. M., D. A. Clark, C. E. F. Clark, C. D. Waugh, C. G. Roach, E. K. M. Minnée, C. B. Glassey, S. L. Woodward, D.R. Woodfield, and D. F. Chapman. 2017. A comparison of ryegrass- and tall fescue-based swards with or without a cropping component for dairy production. Animal production, herbage characteristics and financial performance from a 3-year farmlet trial. Grass and Forage Science 72(3): 382-400.

This article was originally published in Technical Series April 2019