We may still have a lot of winter to come but having got our cows milking well now and with no TB tests for a week or two and I have found a bit of time to look ahead the spring and the forthcoming grazing season.

With silage winter stocks tight and a yearning for some sun, there is a danger that some will turn cows out to grass in the next month or two, without giving much thought to how much grazed grass they expect them to eat each day and no idea of how much is available in the fields. I know how this happens – I’ve done it.

You don’t have to wear shorts all year round and speak with a Kiwi accent to manage grass – you just need to start making some simple calculations. Now, although I own a plate meter, I am no grass guru and many with spring calving herds would laugh at my ability to extract milk from grass. But, I’m learning and I understand that the potential to produce milk form grass is enormous if you spend some time managing it right. There are far better sources of information than this blog post – like the guys at DairyCo for example. But, here is some real beginners stuff that might help those aiming to get more out of grass in 2013 to start planning now.

Firstly, grazing is all about supply and demand. How much grass do your cows need and how much can your farm supply?



How much grass do you expect your cows to eat each day? I am told that I should aim to achieve intakes of around 15kg of grass dry matter (DM) a day, which equates to around 80kg of fresh grass depending on how wet the grass is. So, if I have 100 cows in milk all requiring 15kg of DM, I need to do my first simple calculation:

100 cows x 15kg DM = 1,500kg DM per day

This is my daily demand for grazed grass. Now, it is important to remember that this demand will vary throughout the grazing season, depending not only on the number of cows in milk but, also, the stage of lactation, supplementary feeding, weather and other variables. So, you need to reassess what you expect he cows to eat on a regular basis.



What grass is available to your cows through the grazing season? This will depend on tow factors – what area of grass you have available and the rate at which the grass grows. The key objective in this exercise is to match supply to demand. So, once we have established the amount of grass the herd requires we can provide whatever area is required to fulfil their demand.

One of the key things we need to know is grass growth rates throughout the season because these can vary enormously, as illustrated by the table below.

Month Grass Growth
(Kg DM / Ha / Day)*
January 5
February 8
March 20
April 60
May 100
June 80
July 65
August 50
September 45
October 30
November 10
December 5

*Kg of dry matter grown per hectare per day

The figures in the above table are for illustration only. You may achieve higher or lower growth rates on your farm depending on where you farm, the type of grass you have on the farm, what the weather does this year and how much manure and fertiliser you apply to your grass. However, it provides a useful starting point for those with no historical data for grass growth on their farm.


Matching supply and demand

Once we have established how much grass the cows require and the potential grass supply on our farm we can then begin to plan how we will match supply and demand.

Firstly, we need establish how much grass is already in the fields at the time we turn the cows out to graze. A rising platemeter is the ideal tool for this but you can use your welly boot as a guide. Aim to turn the cows out when there is an average grass cover of 2,000 – 2,200 kg of DM per hectare across the farm. This should be sufficient, with reasonable grass growth, to ensure that the cows don’t eat all the grass in a week and then go hungry.

It is important to note that not all of the grass in the field is available to the cows – they won’t eat it right down to the ground. What the cows leave behind is known as the ‘residual’ cover. Most grazing experts say we should move the cows on to the next field when the grass has been grazed down to a residual cover of 1,500 – 1,700kg DM per Ha. So, if the cows go into a field with 2,700kg DM per Ha, the actual grass available to the cows is 1,000kg DM per Ha (2,700 – 1,700).

If there is 2,700kg DM / Ha in a field when we turn the cows in to the field, how many hectares will we need to allocate the cows to meet their demand for grazed grass?

The following calculation illustrates how we can allocate the correct area for grazing each day.

Herd demand: 100 cows x 15kg DM = 1,500kg DM required
Grass cover on entry 2,700kg DM per Ha
Grass cover after grazing 1,700kg DM per Ha
Available grass 1,000kg DM per Ha
Grazing area required: 1,500kg required
1,000kg per Ha available
= 1.5 Hectares per day
(3.7 acres per day)


Planning ahead

Hopefully, you can now see that it is quite simple to assess daily demand and supply for grass on your farm. But, for good grassland management we need to look beyond what we will feed today or tomorrow and this is why continual assessment of grass growth rates is important throughout the grazing season.

If the cows are turned out to grass in March, there may be in excess of 2,000kg DM per Ha cover in the fields but, grass growth is relatively slow at this time and therefore it may be necessary to supplement the cows with silage to meet their total forage requirements. However, when we get to May grass growth is at a seasonal peak and may grow quicker than the cows can eat it. If we have already calculated how much grass we expect there to be on the farm throughout the coming season, we can plan for peaks and troughs in grass availability.

When we can see a surplus of grass building in front of the cows we can take certain fields out of the grazing rotation and cut the grass for conservation as winter forage – then releasing the field back to the cows later in the summer when grass growth rates begin to slow.



This is not intended to be a comprehensive guide to grazing management but, rather, a simple introduction for those who, like me, want to make better use of their grazing in the year ahead.

It is strange that we have always been pre-occupied with measuring things like the use of purchased feeds but have little or no idea of how much grass we feed to our cows. For some, grass has been regarded as somewhere comfortable for the cows to lie in the summer but others have realised that it can make a really significant contribution to the profitability of their herd when managed well.

Free Range Dairy isn’t just about promoting nice images of cows grazing in the sunshine – it is also about farmers helping one another to improve their business without resorting to expensive technology. The opportunities to do this are huge and there is help out there. DairyCo provide a lot of information on grass and it’s very easy to understand. Take a look at their website www.dairyco.org.uk where you will find much better information than I have provided here.

For me the most important thing you should do is get your wellies on and walk those fields. It might be wet and maybe we will have snow next week. But, it’s never too early to evaluate how your grass is looking. It’s all about planning – perhaps you will see some fencing that needs doing, think about how a new gateway here or there would help with access to fields, or think about putting in those bigger water troughs you have been promising the cows.

Don’t spend your life on the concrete – like our cows, farmers were meant to be outdoors!

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