DairyNZ’s feed and farm systems team provide an evaluation framework for making the best decisions around supplement use and pasture surpluses.
Coming into mating there is often a reluctance to stop feeding supplements, even when pasture supply is more than adequate (pasture residuals of 1500-1600kg DM/ha and good pasture utilisation). This year is the time to challenge that reluctance.
We know reproductive performance above industry targets can be achieved on adequate pasture and there are no reproductive benefits from feeding additional supplements.
True surpluses versus making a surplus from N
Identifying and removing pasture surpluses as they develop, and ensuring residuals are maintained as grass begins to enter the reproductive phase, are critical to maintaining pasture quality.
If cows are able to be allocated the appropriate level of pasture to meet their demands then, where possible, saving any supplements on hand or contracted for later in the season makes sense.
Due to the low milk price this year, a common question being asked is, “am I better to apply nitrogen to generate grass surpluses for silage rather than buy in other supplements (to fill the feed gaps later in summer/autumn)?”
The cheapest form of silage is from a true surplus (i.e. it doesn’t require N fertiliser to grow it), and comes in at 1.77c/MJ ME eaten (table 1), and is cheaper than PKE if current spot prices hold until next year.
Using the cost for N grown grass, and adding the cost of harvesting and ensiling the grass grown (shown in Table 1) takes this silage cost to 2.46c/MJ ME eaten. This is less than the price of PKE, assuming the spot price holds at the $245/t quoted in Table 2. But pasture silage will provide additional protein which may be important in droughts or for some partial/total mixed ration diets. However, even if a supplement price was cheaper than ensiling the true surplus, there is a going to be a reduction in quality from deferring the surplus to graze later, and the total pasture grown will suffer. Hence deferred grazing needs to be carefully planned and managed, and it is perhaps safer to ensile the surplus if it can be afforded.
TABLE 1: COST OF GRASS SILAGE Cost of silage grown from true surplus 1.51c/MJ ME Cost of silage eaten from true surplus 1.77c/MJ ME Nitrogen applied to generate surplus $0.07/kg DM ($130/ha) Average yield of silage or hay/ha 2000kg DM/ha Harvesting cost $0.10/kg DM ($200/ha) Ensiling and stack loss 5% * Feeding out costs $0.07/kg DM ($133/ha) Wastage in feeding out 10%** Silage eaten 1710kg DM/ha MJ ME/kg DM pasture silage 11 MJ ME Cost of silage grown from N 2.11c/MJ ME Cost of silage eaten from N 2.46c/MJ ME
*5% ensiling and stack losses only achievable under excellent conditions.
**10% wastage feeding out in a paddock only achievable under excellent conditions.
TABLE 2: COST OF PKE Price $245/t applied DM/t 900kg DM/t (90% DM/t) Wastage in feeding 10%* PKE eaten/t PKE fed 810kg DM feeding out costs - paddock
(in-shed lower cost)
$0.07/kgDM MJ ME/kg DM PKE 11.4MJ ME Cost of PKE eaten 3.27c/ MJ ME
*10% wastage assuming excellent storage and good utilisation from feeding in bins.
For farmers with PKE contracted for the year, paying a storage cost of $6/t/month still means the PKE will be cheaper than many other feeds, even if held over to summer or autumn. This provides the opportunity to delay taking the PKE if surpluses are present.
Points to consider include: what is the likelihood of the supplement being required? How long can your contract be extended? It may also be a cheaper option to consider on-selling the contract to someone else who needs it.
- Pasture is sufficient for good reproductive performance.
- If energy is limiting, choose the cheapest source of feed.
- The cheapest source of feed is silage from true surplus, followed by N grown silage, followed by PKE (at $245/t).
- If storage costs are being paid for contracted PKE consider if you are likely to need it later.
This article was originally published in Inside Dairy October 2015