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One of the most common questions asked at the Irish Farmers Journal grassland management courses was how much area to give the cows.
For many farmers, it’s a guess and they adjust it from there. The problem with guessing is that the allocation will be wrong way more often than it will be right.
The result being the cows will be overfed or underfed most of the time. This article explains how to remove the guesswork and get it just right.
There are a few ways of doing this. The following are two example approaches.
1. Work out how many cows are going grazing and how much grass they are going to eat per grazing. For example, 15 cows eating 4kg of grass per grazing means the total amount of grass being allocated is 60kg of dry matter.
2. Work out the area of the paddocks and the amount of grass in it. For example, a 0.75ha paddock with a cover of 900kg/ha means the total amount of feed in the paddock is 675kg.
3. Divide the daily allocation by the total amount of feed in the field to work out how many grazings are in the paddock. In this example, there are 11 grazings in the paddock. Therefore, allocate one 11th of the paddock for that grazing.
This example is more suitable when cow numbers are changing regularly or where grass covers differ across the field.
1. Work out how many cows are grazing and how much grass they are eating in the 12-hour break. For example, 15 cows eating 4kg is a total demand of 60kg.
2. Work out how many square metres are needed to give 1kg of grass dry matter. To do this, divide the cover into 10,000. For example, a cover of 900kg into 10,000 is 11.1 metres square per kilo of dry matter. The higher the cover of grass, the lower the number of metres to get 1kg of dry matter.
3. Multiply this number by the demand to work out the total allocation. So in this case, 11.1 multiplied by 60kg is 666 metres square. This is how much area you need to give the cows.
4. To work out where to put the fence, measure the width of the paddock and then divide this into 666. For example, if the paddock is 75m wide, the strip wire should be placed 8.9m back.
Tweaks
Allocating the grass is only half the job. The amount of area being allocated daily needs to be tweaked, as cow intakes change constantly and so too does the amount of grass in the paddock.
Farmers should be looking at post-grazing heights and changing the allocation accordingly.
Stephen Connolly is co-ordinating the grassland management courses. There are still places available in some areas. He can be contacted on 087-669 6490.
The Grass+ page returns to the Irish Farmers Journal print edition of the paper this week.
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