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On the 13th March 1998 the North Down Grassland Management Team traveled up to Greenmount College to view the extended grazing in operation there and take a short course in grass budgeting.. The cows had been out for about 2 weeks at the College.
Dr. David Patterson Grass Technologist at Greenmount and Gareth Gormely co-ordinator of the North Down Grassland Management Team took the group out to the paddocks. Unfortunately bad weather came shortly after turnout and there has been an element of poaching in some of the paddocks. |
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In order to try and minimise poaching the cows had been driven to the furthest end of the paddock and a back fence had been used. One problem associated with pugged pasture is that it is impossible to get an accurate reading of the residual with a rising plate meter since the foot of the meter will often slide into a hoof print. David Patterson suggested that it would be better not even trying to measure pugged pasture with a plate meter but rather estimate the cover by eyeballing instead. The damage in the paddocks at Greenmount was as much as any of the group had seen on the farms and the hoof prints were deeper than those in the Ards. However the group considered the damage to the ground tolerable. It should also be pointed out that it was only a couple of areas that were grazed in wet weather that had any significant damage at all.
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David Patterson then gave the group an explanation of how grass budgeting could be used to help make informed decisions on when to turn out, how long to turn out and what area should be allocated.
The group examined a number of paddocks at the college and estimated the dry matter cover and compared this to plate meter readings. A number of points were made. The grass cover within a single paddock could vary considerable. Often heavier covers around the edge of a field and particularly at a gate could mislead farmers into thinking they had more grass than they really had. It was also suggested that the same route should be used each time to try and maintain a consistency in the readings. |
| The group examined the first paddock to be grazed. There was no poaching at all on this ground and as can be seen from the photograph there had been very good regrowth. |
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The group then went to the Greenmount Internet Suite to draw up grass budgets for their own farms using Excel.
They used current average farm covers along with expected calving pattern and estimated growth rates to try and determine the best strategy for their grazing. Most of the group hoped to be out day and night in early April. With some members able to go out before that. Those members with Excel at home where able to save their budgets onto disk so they could update their budgets at home with actual farm covers and more accurate growth rates. Others took a print out of their grass budget home for reference. |
An example of a grass budget
Date
Each row represents a time period (1 or 2 weeks). The dates displayed in this column are the last day in each time period.
Area
This is the amount of land (measured in hectares) allocated for grazing the dairy herd (i.e. excluding young stock and silage ground).
Growth
This is the expected grass growth rate in kilograms of drymatter per hectare per day. This figure will vary depending on weather conditions and fertiliser application. Recent years have seen a dramtic increase is early spring growth rates.
Supply
By Multiplying the area with the expected growth we can estimate total grass supply in any given time period.
Milking Cows
The number of milking cows at grass.
Grass Intake
This is the number of kilograms of dry matter of grazed grass that the cow will eat in one day. This will depend upon grass cover, area allocated (stocking density), and the length of time the cows are allowed to graze for. Cows out for 3-4 hours can eat between 3 - 5 kgDM. Cows out all day (i.e. from Morning to evening milking) can eat between 8 - 10 kgDM. Cows out full time with no silage being fed can eat in excess of 17 kgDM.
Demand
This is worked out by multiplying the cow numbers by intake per cow.
Change in Cover
By subtracting demand from supply we can work out the change in average farm over a set period.
Average Cover
This is the expected average farm cover at the end of the time period. We can compare these to predefined targets for average farm cover at various times of the grazing calendar.
Grazing Days
This is a function of herd demand and the amount of grass available on the farm above a typical grazing residual achieved by the cows (usually about 1500-1600 kgDM/ha). Basically if grass growth stopped this is the length of time it would take the cows to eat off all "available" pasture.
Stocking Rate
This is simple the number of cows per hectare of grazing ground. Typical late spring / early summer stocking rates in Northern Ireland are between 5 - 6 cows/ha.
Liveweight Per Hectare
Of more use to beef and sheep farmers this estimates the amount of liveweight per hectare. The formula can be adjusted depending on the size and breed of the cows.
