Archive: Deferred grazing

Published 12 September 14

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Deferred grazing, an autumn opportunity

Autumn grown grass can be utilised well in the diet of the lactating cow if it’s managed well, and with information on how much stock are eating, says DairyCo technical extension officer Piers Badnell.

However, even at 12 ME it does not feed as well as spring grass, partly because of dry matter intakes (DMI) and for some with cows on autumn grass it may not be suitable. So what do you do with autumn grass if that is the case? By not doing anything you could carry too much cover into the winter, and end up with substandard pasture in the spring. This means you will not realise the profit potential  (see Picture 1 below).

Long _grass _over _winter

Picture 1: Spring grass showing the effects of too much grass over the winter.

Graph 1 shows this year’s growth rates compared to the five-year average. At the moment, with rates between 60 and 80kg DM/ha, they are above the five-year average. 

GG averages

Graph 1: 2014 grass growth average against averages for 2009-2013

Source: DairyCo Forage for Knowledge

With the fair weather set to continue, many of you could end up with a lot of grass. What are your options?

1. Silage – Do you need it? If not, there are costs to be paid. However, it can make anywhere in the range from good to very poor silage (link to autumn silage article).

2. Graze it – There is milk in it if you understand what it can and can’t do.

3. Defer it – For dry and youngstock.

Option 3 allows you to turn the grass growth into cost savings over the autumn/winter period.

Deferred grazing

If you are looking to defer grazing, rather than making late cuts of silage, shut up parcels of grazing land, perhaps on the perimeter of the grazing platform, from the end of August/beginning of September. Keep the cows off these areas until the middle of November, and then use the ground for grazing in-calf heifers, yearlings and dry cows. This dramatically reduces feed and housing costs.

As autumn grass growth rates can vary considerably, you need to be flexible in your approach when it comes to when and how much land to shut up. However, there are now excellent growth rates, so predicting the required amount is potentially easier. Still shutting a bit gives you more options.

With silage costs two to three times higher than grazing, and housing costs between £0.50 and £1.70 per day for milkers, it is reasonable to estimate a cost of £0.50 plus a day for heifers. Calculate your own figures to check if it is worth your while.

Letting the cows harvest the grass where it is, greatly reduces feed and housing costs, eg slurry disposal, bedding and diesel. Some producers who utilise deferred grazing divide the stock into small groups to minimise soil compaction and making a mess. Because of this, it probably has similar labour requirements to housed cows.

It’s important to understand what deferred grazing can provide nutritionally. From November onwards DM can range from 18 - 19% in dry conditions, to 14 - 15% in wet, ME will be around 11 MJ/kg DM. Therefore, a seven month old, 200kg heifer, which requires an average of 50MJ/day of energy for maintenance, needs 4.54kg DM/day to achieve the target live weight gain. 

As said earlier, if left grass maintains quality in the autumn, this is unlike spring time. This is because, in the spring, grass grows very quickly and the plant only has three live leaves. Short leaf appearance rates (can be between six and ten days due to warm weather, warm soil temperatures and good growing conditions) mean that if the grass is not grazed at a suitable round length (18 -25 days) dead leaves accumulate at the base of the sward and stem, dropping quality. In the autumn, once the sward has grown from now to mid-November, the temperature drops and day length reduces. This slows down growth and leaf appearance goes up to 30-40+ days. There is also far less dead leaf in the base of the sward. The plant is almost being held in ‘suspended animation’ waiting to be utilised through autumn and possibly early winter.

If not utilised in this period, degradation will occur eventually and compromise early season growth and quality.

Two years ago, some deferred grazing of a producer in Dorset was analysed. The results were: 11.6 ME, 16.2% CP and 23.5% DM. The DM was high and a reflection of a dry day. See pictures 2 and 3 below.

Heifers _deferred _grazing _1   Heifers _deferred _grazing _2
Pictures 2 and 3: Heifers deferred grazing taking place

If grass is grazed normally at this time of year, DM is in the top teens on a dry day and about 15% on a wet one. So will this provide adequate DMI for the heifers? In the example of a 200kg heifer, this is achievable. But you should measure and calculate grass consumed on a DM basis by plate metering to see what entry cover and residuals are to give, utilised per hectare. Combined with the area of the allocation, the DM figure per head can be calculated.

A grass sample sent to a lab (inform them it’s grazing as they may assume it is a silage sample) will give clarity. You can then calculate if the animal is getting enough, and if supplementation is needed.  

On the same principle, for an older animal that can eat 3% of its body weight, the calculation stands firm. A 300kg animal, at 3% of its body weight is 9kg dry matter. This knowledge is imperative so that we can be confident the animal is getting enough feed, in terms of both quantity and quality, to grow. If she does not hit the targets to calve at two years then it would be a false economy.

An example of working out the area needed in deferred grazing:

50 heifers eating 5kg DM day equals a demand per day of 250kg DM.

Deferred grazing top cover of 3,500kg DM/ha and stock grazing to 1,800kg DM/Ha = 1,700kg DM/ha available.

1,700 divided by 250 = 7 days to graze a hectare.  

With 10 hectare available, there are 70 days to graze.

Monitor animal growth and performance, and supplement if necessary. Deferred grazing is likely to do much more than you expect, so question yourself before going to concentrate. Do they need it and, if so how much? Feeding+ chapter 10 has tables of withers height for age targets. Withers height is a very good and simple way of monitoring growth rates. 

Deferred grazing action list

  • Shut up parcels of grazing land from the end of August/beginning of September ready to graze mid-November.
  • When grazing on a slope, always graze from the top down.
  • Graze in small groups to help reduce damage to soil. When using deferred grazing, work with the slope in fields, getting cows to graze at the top during wet weather and at the bottom during dry periods. By grazing a square, rather than a strip, the stock make less mess as they’re not repeatedly pacing the same strip. As seen in picture 4.

Richard _harbord
Picture 4: Deferred grazing in a square 

  • In some cases, there may be an impact on next season’s early grazing, especially if you are highly stocked (spring/early season grass makes money, don’t compromise this). Take this into account when deciding which areas to use and, if possible, think about using ‘sacrifice’ pasture that is due to be reseeded in spring. Any fields that are underperforming now could well be used, as an April reseed which will correct any compaction and enable stock to be kept out later.
  • Grass quality will depend on weather conditions this autumn but always monitor growth rates and add extra feed, if necessary.
  • Be aware that in harsh, wet and windy conditions, a heifer’s maintenance energy requirements will be greater, so keep an eye on conditions and how exposed the site is.
  • Be flexible in your approach to deferred grazing, as autumn grass growths can vary hugely.