Measuring grass using a simple system brings major advantages

John Large

John Large

What a difference one year can make. This time last year we were still feeding nuts and fodder-beet to lambed ewes. The only ewes getting any food but grass this spring are the few triplets and hoggets with twins.

By the end of March our grass was almost all eaten. To boost growth, 1 1/4 bags of 24-2.2-4.5 were spread on any ground that was grazed. The response has been really good with growth of 45kg/day recorded.

I measured grass with a plate metre. Firstly, record the number on the plate metre (eg 11,029). Then take 10 measurements randomly throughout the paddock.

This could give a recorded number (eg 11,141). To do your sum, subtract the first number from the second number and divide the answer by 20 to get the height of the grass.

11,141 - 11,029 = 112 ÷ 20 = 5.6cm.

This is your overall grass height so you subtract what will not be eaten. We aim to leave 3.5cm behind so there is 2.1cm to eat. Each centimetrein height is 200kg/ha, which gives 420kg/ha. Multiply by the size of the paddock -- 1.5ha gives 630kg of grass.

5.6cm - 3.5cm = 2.1cm x 200kg x 1.5ha = 630kg

Now allow for what each ewe will need to eat. A ewe rearing twin lambs of four weeks old needs 3kg/day. So a group of 50 ewes will need 150kg/day. We divide our total cover that will be eaten by our daily requirement (630kg ÷ 150kg) to give us 4.2 days grass for the 50 ewes and their lambs. I hope to manage my grass by using this method for this year. I will know when I have too much grass and I can take out paddocks for baled silage, and when there's not enough I can adjust numbers, spread fertiliser or wean the lambs earlier.

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The advantage of measuring grass for me is better quality, less fertiliser, knowing what grass is ahead of each group and allowing me to sell lambs earlier and leave more grass for ewes later in the year.


Lambs are doing very well on good grass and plenty of milk from their mothers. Our next big job will be giving the lambs their first dose.

This will be a levamisole-type drench at about 5-6 weeks and it is for nematodirus worms. I hope that this dose will be given the same day as the lambs will be weighed. This 40-day weight is recorded using an electronic weigher with the electronic tags in the lambs linking them to their birth weight and parentage.

The hoggets and repeat ewes are still lambing, with about 20 of each left. We've had no problems with the ewes but the one-year-old hoggets again suffered because no enzootic abortion vaccine has been available. From 94 in-lamb at scanning, we hope 78 rear lambs. This is very disappointing to have 16 without lambs, and means a loss of potential income in a year where lamb prices look good. If this vaccine is unavailable next year, I definitely will not lamb ewe-lambs.

These all lambed outside by day and in the shed at night. A small amount of meal was given when they came indoors in the evening. This worked out very well to train them to come to the shed. We had some big single lambs that needed some assistance and a few trips to the vet.

The one good thing was that they all looked after their lambs well, no running away after giving birth or not letting the lambs suck. The twins are now on good grass getting 0.5kg of meal and the lambs will get creep from next week.

The singles are on grass only. Both groups will be joined together in another few weeks and all the lambs will get creep fed, with the lambs weaned at 12 weeks to give their mothers more time to put on weight before mating again. Just on a personal note to someone who taught me something very important at lambing -- patience. Happy birthday Mam.

John Large is a sheep farmer at Gortnahoe, Thurles, Co Tipperary

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