WORKING OUT FEED BUDGETS

31 January 1997




WORKING OUT FEED BUDGETS

Maximising use of grazed grass will demand careful pasture management this season

GRASS planning – otherwise known as grass or feed budgeting – is about estimating how much grass is available and how long it will last your stock, explains New Zealand grazing consultant Paul Bird.

It ensures full use of grazed grass as the cows main source of feed by identifying grass surpluses, and deficits, before they happen.

When average farm cover gets too high, above 2700kg DM/ha, grass regrowth will be restricted and pastures will become open. When average farm cover drops below 1600kg DM/ha grass re-growth will be severely restricted. By monitoring grass cover regularly early action can be taken to get back on track, says Mr Bird.

When grass cover is getting too high management options include: Cutting silage, reducing nitrogen, increasing animal intake through rotation length, increasing stocking rate. When grass cover is going too low options include: Feeding silage/concentrates and slowing the grazing rotation, increasing nitrogen, reducing stocking rate.

Grass covers are usually measured on a per hectare basis, but more useful is how much feed is in a paddock or on the whole farm he says. For accurate grass planning the exact area of the paddock or farm must be known. Then multiply the pasture cover in kg DM/ha by the paddock size to find the total amount of feed available.

For example, if the total pasture cover in a paddock is 2500kg DM/ha, and the paddock is 1.3ha – the total DM in the paddock is 1.3 x 2500 which is 3250kg DM. To estimate the average farm cover do the same calculation for each paddock on the farm and divide the total by the farm area.n


GRASS COVER DEFINITIONS

&#8226 Kilograms of dry matter per hectare (kg DM/ha). This is the total quantity of DM on one hectare when the grass has been harvested right down to ground level. Not all this DM can be used

by the cows.

&#8226 Residual grass cover (kg DM/ha). When cows graze a pasture they always leave some grass behind. This is the residual pasture cover. It varies tremendously between seasons.

In winter, when cows are eating down low, pasture dry matter is low and there is little build up of dead material. Residuals can be as low as 1000kg DM/ha.

Milking cows should be leaving grass residuals of about 1500-1700kg DM/ha.

&#8226 Available grass (kg

DM/ha) is the difference between total grass cover and residual grass cover – the amount of pasture the cows actually eat.


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