The 5 steps to managing a grass rotation

The cost of keeping cows inside could make many producers think more seriously about getting more from grazed grass this season. Aly Balsom speaks to DairyCo extension officer Piers Badnell to find out how to manage a grazing rotation.

“Everyone has the potential to get more from grazed grass – the cheapest feed available. It will vary from farm to farm as to how much is achievable from grazing, but the key is to challenge yourself as to when cows go out.

“Most producers will make more money if they push the quality and quantity of grazed grass.”


• Under optimum conditions grazed grass has the potential to deliver 17-18kg DM a cow a day. At 12ME this could produce 25 litres Maintenance + (Mn+)

• Grass can deliver 12ME from February through until November, along with good protein levels

• Farmers need to be aware DM will be affected by rainfall and adjust rations accordingly

• Combining DM and ME with how much cows are eating can allow accurate prediction of what Mn+ can be achieved – the key is to know how much to allocate

• On a farm new to rotational grazing, with 150 black and white cows, yielding 7500 litres, aim for 12kg DM a cow a day throughout the season

• When you become more experienced, push for 14-15kg DM a cow a day


• Housing costs, excluding feed costs, range from 56p a cow a day to 170p a cow a day

• At £1 a day for a 100-cow herd, this equates to a £1400 saving by extending the grazing season by two weeks


• Don’t have a fixed turn out date in your head – walk the farm and assess how much grass you have – most producers will have more than they think

• Always try and get cows out earlier than previous years

• Increasing grazed grass in the diet should be viewed in the same way as setting up a winter ration – analyse grass fortnightly so you can accurately determine how much supplementation is needed throughout the season

• Whenever cows start to go out, start them off on 5kg DM a cow a day from grazed grass so there is no rapid change in diet – this should take her 3-4hrs to graze

• Aim to get cows out in February or at least two weeks earlier than usual – this will help set the grazing wedge up earlier

• Early grazing is probably best for in-calf, mid-late lactation cows


• The key is to allocate cows what you want them to graze, rather than giving them a choice

• Aim to have 20-30 grazing areas – you may only have five fields, but these can be split up into areas

• You don’t have to spend a fortune on set-up if you’re just starting out with a rotation – you can still get more from grass

• When thinking seriously about a rotation – think about investing more in tracks and water troughs


• Ideally you want all your fields at different stages of grass growth

• Grass should be grazed at the 2.5 to 3-leaf stage for maximum efficiency

• Cows should start grazing a field when grass cover is at 2700-2800kg DM/ha

• Grass should be grazed down to 1500kg DM/ha

• Overall, average farm cover should be about 2200kg DM/ha

• Each grazing rotation (around all fields) is likely to be an average 25-30 days

• At peak growth, the round may take 15-18 days, with the round extending to 30 days when growth slows

Tools to achieve a grass wedge

• Using a rising grass plate meter to assess farm grass cover allows a grazing wedge to be accurately set up

• The plate meter provides kg DM/ha figures for individual fields – these can then be inputted into computer software to produce a grazing wedge which can be used to determine which fields should be grazed or taken out for silage

• Walking the farm weekly and collating figures provides early warning as to whether you are likely to see a grass surplus or shortage in 10 days’ time

“Relying on grass height alone can give an inaccurate picture of grass cover,” says Mr Badnell. “Counting the leaves will give a better idea of whether a field is ready to be grazed – when a field has been grazed consistently all over, you will only need to count 2-3 plants to get an idea of cover.”

However, according to Mr Badnell, a plate meter is by far the best means of setting up a grass wedge. “The plate meter is equivalent to the weigh scales on the mixer wagon, providing you with actual figures you can use to calculate feed requirements.”


Assessing supply and demand is essential in managing the grass wedge:

Demand = Number of cows x required kg DM a cow a day from grass

for example, 150 cows x 15kg DM a cow a day = 2250kg DM demand

Supply = Total hectares of grass available x grass growth rate (Growth rate can be easily calculated when comparing covers from week to week using a plate meter)

for example, 45ha x 45kg DM growth a day = 2025kg DM supply

= This gives a 225kg DM shortfall

• In a period of high growth rate, grass could easily get ahead of you, so this in-balance could be in your favour

• Or to tackle this shortfall, you could alter the supply and demand calculation – can you reduce demand? Equally if supply outstrips demand, could you up the amount needed from grass or take more fields out for silage.


“A grazing residual of 1500kg DM a hectare should be the aim, although it is not necessarily easy to achieve, but there are a number of ways of encouraging cows to graze effectively,” says Mr Badnell.

• Ensure cows are put in front of good quality, fresh grass

• Mowing can be used to reinstate the residual – for example, when a high cover field is not grazed well, it can be mowed down the 5cm to reinstate optimum cover

• When you make a mistake in April, mowing can correct the grazing wedge and have a return on investment. However, doing the same in July, will be purely cosmetic

• Don’t put cows into a field above 2800kg DM/ha – she will waste it and then grass will be poor quality

• Cows should go out on the edge of appetite, not with a belly full of TMR

• Select grass varieties with good palatabilities

• Ensure cows go out to something fresh after milking

• Cows not used to grazing may stand at the gate for a couple of days and bellow – don’t listen, they will learn to graze, as long as what you put in front of them is quality.


A grass rotation: The basic principle

Setting up a grass rotation works on the principle of rotating stock between paddocks depending on grass growth.

Ideally you want all your fields at different stages of grass growth (some which have just been grazed and others that are ready to be grazed)

This gives you more control over grazing intakes and allows you to achieve maximum grass quality by grazing paddocks efficiently.

More online

• To see how a Wiltshire family manages a grass rotation in their herd of high yielding Holsteins

• Keep up to date with how grass is growing in your region and get technical advice on grazing management at GrassWatch

• Read about how mowing in front of cows can extend the grazing rotation

See more