Past and current grazing experiments inform how to best manage pasture – and shows in a high milk price year that the first 85 percent of the operating profit comes from the base pasture, 10 percent from N fertiliser use and the last 5 percent from supplements.
Past grazing experiments by Dr Arnold Bryant and the Ruakura team revolutionised the way pasture was managed through winter and spring (detailed in DairyNZ’s June 2016 Technical Series).
Following a series of ground-breaking trials, in 1999 Arnold and colleague John Penno set up the 1.75t MS/ha trial, aimed at achieving 1750kg MS/ha and investigating the costs.
It measured the increase in per-cow and per-hectare milksolids (MS) production when total feed supply is increased by bought-in supplements and/or nitrogen (N) fertiliser. A range of combinations were used to increase pasture growth with N, supplements bought in and an increased stocking rate to use the extra feed.
The results indicated it was uneconomic to add extra feed to a system with good pasture utilisation, unless the stocking rate was increased and cheap feed available. This was very evident in the lower stocked herds (less than 3.4 cows/ha).
At this stocking rate, the increase in milksolids production did not reflect the large increases in feed supply. Increasing feed supply for most of the year reduced pasture utilisation.
The biggest responses were near the end of lactation – extra days in milk allowing for increased production at the end of the season.
So where are we today?
DairyNZ research and development general manager Dr David McCall says the pasture/supplementary debate has been polarising and confusing for some farmers.
“The pasture first concept is about managing pastures regardless of farming system. Modelling has shown that getting pasture management right is worth over $300/ha, even at today’s milk prices.”
In the 1.75t MS/ha trial, the control farmlet (no N applied) was producing 1000kg MS/ha. Using N fertiliser allowed an additional 200kg MS/ha to be produced and supplement use (maize silage) with increased stocking rate added another 400kg MS/ha.
David has re-analysed the trial results with today’s costs and milk prices.
Operating profit at $7.00/kg MS
When comparing these differing farm systems at $7.00/kg MS, 85 percent of the operating profit came from pasture, 10 percent from N fertiliser use and 5 percent from supplements (Figure 1).
“Clearly it’s more important to get things right in something that contributes 85 percent of the profit, before something that contributes the last 5 percent,” says David.
Operating profit at $4.00/kg MS
When calculating at $4.00/kg MS, N use only increased the operating profit by 2 percent and the supplement groups made a loss (Figure 1).
This suggests farmers need to focus on optimising pasture management and be very careful about adding costs that may not give economic returns. David adds that it makes sense to have a supplementary feed source as insurance feed for dry cows in autumn but not to push production at a $4 milk price.
This article was originally published in Inside Dairy August 2016