19 April 1996

Good planning is secret to successful grass use

In the first of a two-part look at reducing production costs for cattle we examine how to plan grass use this season for grazing and conservation. Jonathan Riley reports

GOOD grass management depends on a field-by-field plan for the whole season.

For best results this should be drawn up before grass growth starts, and without prior knowledge of summer weather conditions, says beef consultant David Allen.

"Those who keep simple records of grazing cattle movements between fields, cutting dates, and the amount of silage made from each cut will be best placed to plan ahead," says Dr Allen.

Hectares required for grazing can be calculated by dividing the average weight of cattle during the grazing period by the target total weight of cattle stocked to the hectare.

Conservation areas are calculated from the tonnage that must be made from each cut divided by expected yield a hectare.

The tables show an example for 18-month beef with a silage requirement of 5.5t a head. Two cuts of silage are taken with first cut yields of 20t/ha (8t/acre) (60% of total silage) and 14t/ha (5.6t/acre) (40%) from the second cut. Weight of cattle stocked is 2400kg/ha (971kg/acre) early in the season, 1800kg/ha (728kg/acre) in mid-season and 1500kg/ha (607kg/acre) late in the season.

Dr Allen explains that the example reflects the well-known story of grass under pressure mid-season. When only 0.25ha a head is available in mid-season and grazing is given first priority, second cut silage can only be 0.11ha x 14t/ha or 1.5t. This leaves a shortfall of 0.7t. Options to make up this shortfall, says Dr Allen, without restricting grazing include:

&#8226 A third cut from part of the area in late season if cost is justified.

&#8226 Increase the area allocated to first cut to 0.21ha (0.52 acre).

&#8226 Reduce silage needs in the finishing winter by feeding more cake. &#42


Grass budget for

18-month beef

Grazing

CattleTotalArea

weightweightrequired*

Season(kg)(kg/ha)(ha)

Early20024000.08

Mid25018000.14

Late32515000.22

*Divide average cattle weight by weight of cattle stocked.

Conservation

SilageYieldArea

requiredrequired*

(t)(t/ha)(ha)

1st cut3.3200.17

2nd cut2.2140.16

*Divide tonnes silage required a head by average yield a ha.

Integration

GrazingCons-Area

ervationrequired

SeasonUnitshaha

Early0.080.170.25

Mid0.140.160.30

Late0.22-0.22

To calculate grazing area divide average weight of cattle during grazing period by weight of the cattle stocked on each hectare.